Increased (ectopic) all-trans retinoic acid concentration

65277-42-1

XMAYWYJOQHXEEK-OZXSUGGESA-N

Ketoconazole

, 2R,4S- Piperazine, 1-acetyl-4-[4-[[(2R,4S)-2-(2,4-dichlorophenyl)-2-(1H-imidazol-1-ylmethyl)-1,3-dioxolan-4-yl]methoxy]phenyl]-, rel- (.+-.)-Ketoconazole Brizoral cis-1-Acetyl-4-[4-[[2-(2,4-dichlorophenyl)-2-(1H-imidazole-1-ylmethyl)-1,3-dioxolan-4-yl]methoxy]phenyl]piperazine Ethanone, 1-[4-[4-[[(2R,4S)-2-(2,4-dichlorophenyl)-2-(1H-imidazol-1-ylmethyl)-1,3-dioxolan-4-yl]methoxy]phenyl]-1-piperazinyl]-, rel- Fungarest Fungoral Ketoconazol Ketoderm Ketoisdin Ketozoral Nizoral Onofin K Orifungal M Panfungol Piperazine, 1-acetyl-4-[4-[[2-(2,4-dichlorophenyl)-2-(1H-imidazol-1-ylmethyl)-1,3-dioxolan-4-yl]methoxy]phenyl]-, cis- Piperazine,1-acetyl-4-[4-[[(2R,4S)-2-(2,4-dichlorophenyl)-2-(1H-imidazol-1-ylmethyl)-1,3-dioxolan-4-yl]methoxy]phenyl]-, rel-

DTXSID7029879

115575-11-6

UGFHIPBXIWJXNA-UHFFFAOYNA-N

UGFHIPBXIWJXNA-UHFFFAOYSA-N

Liarozole

DTXSID9048277

80-05-7

IISBACLAFKSPIT-UHFFFAOYSA-N

Bisphenol A

BPA 4,4’-Propane-2,2-diyldiphenol Phenol, 4,4'-(1-methylethylidene)bis- (4,4'-Dihydroxydiphenyl)dimethylmethane 2,2-Bis(4'-hydroxyphenyl) propane 2,2'-Bis(4-hydroxyphenyl)propane 2,2-BIS-(4-HYDROXY-PHENYL)-PROPANE 2,2-Bis(4-hydroxyphenyl)propane 2,2-Bis(p-hydroxyphenyl)propane 2,2-Di(4-Hydroxyphenyl) Propane 2,2-DI(4-HYDROXYPHENYL)PROPANE 2,2-Di(4-phenylol)propane 4,4'-(1-Methylethylidene)bisphenol 4,4'-Bisphenol A 4,4'-DIHYDROXYPHENYL-2,2-PROPANE 4,4'-isopropilidendifenol 4,4'-Isopropylidendiphenol 4,4'-Isopropylidene bisphenol 4,4-ISOPROPYLIDENE DIPHENYL 4,4'-Isopropylidenebis[phenol] 4,4'-isopropylidenediphenol 4,4'-Methylethylidenebisphenol Bis(4-hydroxyphenyl)dimethylmethane Bis(p-hydroxyphenyl)propane BIS[PHENOL], 4,4'-(1-METHYLETHYLIDENE)- BISPHENOL, 4,4'-(1-METHYLETHYLIDENE)- BISPHENOL-A Diphenol methylethylidene Diphenylolpropane Hidorin F 285 Isopropylidenebis(4-hydroxybenzene) NSC 1767 NSC 17959 p,p'-Bisphenol A p,p'-Dihydroxydiphenylpropane P,P'-ISOPROPYLIDENE DIPHENOL p,p'-Isopropylidenebisphenol p,p'-Isopropylidenediphenol Parabis Parabis A Phenol, 4,4'-isopropylidenedi- Pluracol 245 Rikabanol β,β'-Bis(p-hydroxyphenyl)propane

DTXSID7020182

870093-23-5

SNFYYXUGUBUECJ-HXUWFJFHSA-N

(R)-Talarozole

DTXSID50236074

215543-92-3

JNDVEAXZWJIOKB-JYRVWZFOSA-N

su5402

DTXSID90415361

117-81-7

BJQHLKABXJIVAM-UHFFFAOYNA-N

BJQHLKABXJIVAM-UHFFFAOYSA-N

Di(2-ethylhexyl) phthalate

1,2-Benzenedicarboxylic acid, bis(2-ethylhexyl) ester DEHP 1,2-Benzedicarboxylic acid, bis(2-ethyl-hexyl) ester 1,2-Benzenedicarboxylic acid bis(2-ethylhexyl) ester 1,2-Benzenedicarboxylic acid, 1,2-bis(2-ethylhexyl) ester 1,2-Benzenedicarboxylic acid,bis(2-ethylhexylester) Bis(2-ethylhexyl) 1,2-benzenedicarboxylate Bis(2-ethylhexyl) o-phthalate bis(2-ethylhexyl) phthalate Bis(2-ethylhexyl)phthalat Bis(2-ethylhexyl)phthalate Bisoflex 81 Bisoflex DOP Corflex 400 Di(2-ethylhexyl)phthalate Di(isooctyl) phthalate Di-2-ethylhexlphthalate Di-2-ethylhexyl phthalate DI-2-ETHYLHEXYL-PHTHALATE Diacizer DOP Diethylhexyl phthalate Dioctylphthalate DOF Ergoplast FDO Ergoplast FDO-S ETHYLHEXYL PHTHALATE Eviplast 80 Eviplast 81 Fleximel Flexol DOD Flexol DOP ftlalato de bis(2-etilhexilo) Garbeflex DOP-D 40 Good-rite GP 264 Hatco DOP Jayflex DOP Kodaflex DEHP Kodaflex DOP Monocizer DOP NSC 17069 Palatinol AH Palatinol AH-L Phtalate de Bis (Ethyle-2-Hexyle) Phtalate de bis(2-ethylhexyle) PHTHALATE, BIS(2-ETHYLHEXYL) Phthalic acid di(2-ethylhexyl) ester Phthalic acid, bis(2-ethylhexyl) ester PHTHALIC ACID, BIS(2-ETHYLHEXYL)ESTER PHTHALSAEURE-BIS-(2-AETHYLHEXYL)-ESTER Pittsburgh PX 138 Plasthall DOP Reomol D 79P Sansocizer DOP Sansocizer R 8000 Sconamoll DOP Staflex DOP Truflex DOP Vestinol AH Vinycizer 80 Vinycizer 80K Witcizer 312

DTXSID5020607

302-79-4

SHGAZHPCJJPHSC-YCNIQYBTSA-N

all-trans-Retinoic acid

ATRA Tretinoin all-trans-Vitamin A acid Atragen Aberel (all-E)-3,7-Dimethyl-9-(2,6,6-trimethyl-1-cyclohexen-1-yl)-2,4,6,8-nonatetraenoic acid Retinoic acid (all-E)-3,7-Dimethyl-9-(2,6,6-trimethyl-1-cyclohexene-1-yl)-2,4,6,8-nonatetraenoic acid 2,4,6,8-Nonatetraenoic acid, 3,7-dimethyl-9-(2,6,6-trimethyl-1-cyclohexen-1-yl)-, (all-E)- 3,7-Dimethyl-9-(2,6,6-trimethyl-1-cyclohexen-1-yl)-2,4,6,8-nonatetraenoic acid Acide retinoique Aknoten all-(E)-Retinoic acid all-trans-Tretinoin all-trans-β-Retinoic acid Cordes Vas Dermairol Epi-Aberel NSC 122578 NSC 122758 Retacnyl Retin A Retinoic acid, all-trans- trans-Retinoic acid Tretin M Tretin M, 3,7-dimethyl-9-(2,6,6-trimethyl-1-cyclohexen-1-yl)-, (all-E)- tretinoine tretinoino Vesanoid Vesnaroid Vitamin A acid Vitamin A acid, all-trans- Vitamin A1 acid, all-trans- β-Retinoic acid

DTXSID7021239

23593-75-1

VNFPBHJOKIVQEB-UHFFFAOYSA-N

Clotrimazole

1H-Imidazole, 1-[(2-chlorophenyl)diphenylmethyl]- 1-(o-Chlorophenyldiphenylmethyl)imidazole 1-(o-Chlorotrityl)imidazole 1-[(2-Chlorophenyl)diphenylmethyl]-1H-imidazole Canesten Canifug Clotrimazol Desamix F Diphenyl(2-chlorophenyl)(1-imidazolyl)methane Empecid Femcare Gyne-Lotrimin Gyne-Lotrimin 7 Imidazole, 1-(o-chloro-α,α-diphenylbenzyl)- Lotrimin Lotrimin AF Cream Lotrimin AF Solution Lotrimin Jock-Itch Cream Lotrimin Jock-Itch Lotion Monobaycuten Mycelex Mycelex G Mycelex OTC Mycelex Troche Mycofug Mycosporin NSC 257473 Pedisafe Plimycol Rimazole Tibatin Trimysten Veltrim

DTXSID7029871

84625-61-6

VHVPQPYKVGDNFY-ZPGVKDDISA-N

Itraconazole

3H-1,2,4-Triazol-3-one, 4-[4-[4-[4-[[2-(2,4-dichlorophenyl)-2-(1H-1,2,4-triazol-1-ylmethyl)-1,3-dioxolan-4-yl]methoxy]phenyl]-1-piperazinyl]phenyl]-2,4-dihydro-2-(1-methylpropyl)- Canditral Cladosal 100 Itralek Itrizole Oriconazole Orungal Sempera Spherazole CR Spherazole IR Sporamelt Sporanox Sporonox Traconal Triasporin

DTXSID3023180

86386-73-4

RFHAOTPXVQNOHP-UHFFFAOYSA-N

Fluconazole

FLC 1H-1,2,4-Triazole-1-ethanol, α-(2,4-difluorophenyl)-α-(1H-1,2,4-triazol-1-ylmethyl)-

DTXSID3020627

145040-37-5

GHOSNRCGJFBJIB-UHFFFAOYNA-N

GHOSNRCGJFBJIB-UHFFFAOYSA-N

Candesartan cilexetil

DTXSID5020239

158966-92-8

UCHDWCPVSPXUMX-TZIWLTJVSA-N

Montelukast

Cyclopropaneacetic acid, 1-[[[(1R)-1-[3-[(1E)-2-(7-chloro-2-quinolinyl)ethenyl]phenyl]-3-[2-(1-hydroxy-1-methylethyl)phenyl]propyl]thio]methyl]-

DTXSID9023334

135062-02-1

FAEKWTJYAYMJKF-QHCPKHFHSA-N

Repaglinide

Benzoic acid, 2-ethoxy-4-[2-[[(1S)-3-methyl-1-[2-(1-piperidinyl)phenyl]butyl]amino]-2-oxoethyl]- (S)-(+)-2-Ethoxy-4-[[[N-[1-(2-piperidinophenyl)-3-methylbutyl]amino]carbonyl]methyl]benzoic acid AG-EE 623ZW Benzoic acid, 2-ethoxy-4-[2-[[3-methyl-1-[2-(1-piperidinyl)phenyl]butyl]amino]-2-oxoethyl]-, (S)- NovoNorm Prandin

DTXSID3023552

D005298

MESH fertility

D005298

MESH fertility

GO:0009566

GO fertilization

WIKI decreased

Ketoconazole

2017-05-02T11:08:42

Liarozole

2021-11-11T15:09:02

Bisphenol A

2019-12-29T18:38:03

(R)-Talarozole

2021-11-11T15:10:19

Stressor:282 Ketoconazole

2021-11-11T15:14:29

su5402

To clarify the critical stages of gbx2 regulation in the telencephalon, chemical treatment of zebrafish embryos started between 14 and 17 hpf and gbx2 expression was examined at 18 hpf. Alternatively, chemical treatment was started at 14 hpf and then embryos were washed between 15 and 18 hpf, cultured in the absence of chemicals, and gbx2 expression was examined at 18 hpf. Results showed SU5402  mediated repression of gbx2 expression in the telencephalon and MHB became less significant as the treatment start time was delayed from 14 hpf to 17 hpf, and gbx2 expression was gradually restored with earlier removal of the chemical, showing that FGF signaling is continuously required for gbx2 expression in the telencephalon (Z. Wang et al., 2018).

2021-07-15T09:38:10

2021-07-15T09:44:14

Bis(2-ethylhexyl) phthalate

2016-11-29T18:42:08

all-trans-Retinoic acid

2021-11-11T15:19:24

Clotrimazole

2017-05-17T13:22:09

Itraconazole

2021-11-11T15:02:36

Fluconazole

2017-05-17T13:19:33

Candesartan cilexetil

2021-11-11T15:03:24

Montelukast

2021-11-11T15:03:48

Repaglinide

2021-11-11T15:04:23

WikiUser_28

Vertebrates

WikiUser_17

mammals

WikiUser_1

Wikiuser: Cyauk human, mouse, rat

WikiUser_4

Wikiuser: Blandesmann Human, rat, mouse

10116

NCBI rat

10090

NCBI mouse

WCS_9606

common toxicological species human

Increased (ectopic) all-trans retinoic acid concentration

increased atRA concentration

Tissue

Retinoic acid (RA) function and metabolism RA and retinoid signaling is central for numerous physiological processes, and has important roles within reproduction, vision, development and the immune system (<a href="#_ENREF_11" title="O'Byrne, 2013 #68">O'Byrne & Blaner, 2013</a>). As an important morphogen, the levels of RA is tightly controlled within tissues both spatially and temporally. Both insufficient and excess RA has proven to cause severe adverse effects (<a href="#_ENREF_9" title="Kedishvili, 2013 #35">Kedishvili, 2013</a>). RA homeostasis is maintained by tissue-specific enzymes controlling a 2-step biosynthesis pathway: the precursor retinol is converted into retinaldehyde via retinol dehydrogenases (RDHs). Retinaldehyde dehydrogenases (RALDHs) then irreversibly oxidize retinaldehyde into biologically active RA (reviewed by (<a href="#_ENREF_13" title="Shannon, 2017 #15">Shannon et al, 2017</a>)). RA is removed via degradation to polar inactive metabolites by cytochrome P450 (CYP) family hydroxylases; chiefly CYP26A1, B1 and C1 (<a href="#_ENREF_17" title="Topletz, 2015 #61">Topletz et al, 2015</a>). RA signals through the nuclear Retinoic Acid Receptors (RARs) and Retinoid X Receptors (RXRs) thereby regulating transcription of target genes (<a href="#_ENREF_4" title="Cunningham, 2015 #32">Cunningham & Duester, 2015</a>).   Ectopic RA as Key Event Inhibition or disruption of any of the enzymes in the RA degradation pathway, including the Cyp26 family, lead to increased concentrations of biologically active RA in target cells. Equally, application of RA for medical treatments, including for acute promyelocytic leukemia and cystic acne, lead to increased concentrations of biologically active RA in target cells.

In vitro Indirect measurement of activity and potency of RXRs and RARs is possible via luciferase assays in cell lines, for example (<a href="#_ENREF_3" title="Chassot, 2020 #111">Chassot et al, 2020</a>; <a href="#_ENREF_8" title="Jurutka, 2019 #63">Jurutka & Wagner, 2019</a>).   In vivo Direct measurements of atRA in serum (humans, animals) can be performed by various chromatographic methods (<a href="#_ENREF_7" title="Gundersen, 2007 #67">Gundersen et al, 2007</a>), for instance by high performance liquid chromatography (HPLC) (<a href="#_ENREF_5" title="De Leenheer, 1982 #62">De Leenheer et al, 1982</a>) or liquid chromatography-tandem mass spectrometry (LC-MS) (<a href="#_ENREF_10" title="Morgenstern, 2021 #37">Morgenstern et al, 2021</a>). Indirect measurements in animal models can be performed with various reporter assays with RAR-RXR-RARE or RXR-RXR-RARE promoter elements driving expression of reporter proteins. These reporter assays can detect the presence of ATRA in tissues in a semi-quantitative manner. Examples include reporter mouse lines (<a href="#_ENREF_2" title="Carlsen, 2021 #345">Carlsen et al, 2021</a>; <a href="#_ENREF_12" title="Rossant, 1991 #38">Rossant et al, 1991</a>; <a href="#_ENREF_14" title="Solomin, 1998 #39">Solomin et al, 1998</a>).

The retinoid signaling pathway is highly evolutionary conserved between vertebrates. This KE is applicable for both mammalian sexes, across developmental stages into adulthood, in numerous cells and tissues and across taxa.

High Male High Female

Moderate

Fetal

Not Specified High <a name="_ENREF_1">Bowles J, Knight D, Smith C, Wilhelm D, Richman J, Mamiya S, Yashiro K, Chawengsaksophak K, Wilson MJ, Rossant J, Hamada H, Koopman P (2006) Retinoid signaling determines germ cell fate in mice. Science 312: 596-600</a> <a name="_ENREF_2">Carlsen H, Ebihara K, Kuwata NH, Kuwata K, Aydemir G, Rühl R, Blomhoff R (2021) A transgenic reporter mouse model for in vivo assessment of retinoic acid receptor transcriptional activation International Journal for Vitamin and Nutrition Research In Press</a> <a name="_ENREF_3">Chassot AA, Le Rolle M, Jolivet G, Stevant I, Guigonis JM, Da Silva F, Nef S, Pailhoux E, Schedl A, Ghyselinck NB, Chaboissier MC (2020) Retinoic acid synthesis by ALDH1A proteins is dispensable for meiosis initiation in the mouse fetal ovary. Sci Adv 6: eaaz1261</a> <a name="_ENREF_4">Cunningham TJ, Duester G (2015) Mechanisms of retinoic acid signalling and its roles in organ and limb development Nat Rev Mol Cell Biol 16: 110-123</a> <a name="_ENREF_5">De Leenheer AP, Lambert WE, Claeys I (1982) All-trans-retinoic acid: measurement of reference values in human serum by high performance liquid chromatography. J Lipid Res 23: 1362-1367</a> <a name="_ENREF_6">Esteban J, Serrano-Maciá M, Sánchez-Pérez i, Alonso-Magdalena P, Pellín MC, García-Arévalo M, Nadal A, Barril J (2019) In utero exposure to bisphenol-A disrupts key elements of retinoid system in male mice offspring. Food Chem Toxicol 126: 142-151</a> <a name="_ENREF_7">Gundersen TE, Bastani NE, Blomhoff R (2007) Quantitative high-throughput determination of endogenous retinoids in human plasma using triple-stage liquid chromatography/tandem mass spectrometry. Rapid Commun Mass Spectrom 21: 1176-1186</a> <a name="_ENREF_8">Jurutka PW, Wagner CE (2019) Methods to Assess Activity and Potency of Rexinoids Using Rapid Luciferase-Based Assays: A Case Study with NEt-TMN. Methods Mol Biol 2019</a> <a name="_ENREF_9">Kedishvili NY (2013) Enzymology of retinoic acid biosynthesis and degradation. J Lipid Res 54: 1744-1760</a> <a name="_ENREF_10">Morgenstern J, Fleming T, Kliemank E, Brune M, Nawroth P, Fischer A (2021) Quantification of All-Trans Retinoic Acid by Liquid Chromatography-Tandem Mass Spectrometry and Association with Lipid Profile in Patients with Type 2 Diabetes. Metabolites 11: 60</a> <a name="_ENREF_11">O'Byrne S, Blaner WS (2013) Retinol and retinyl esters: biochemistry and physiology. J Lipid Res 54: 1731-1743</a> <a name="_ENREF_12">Rossant J, Zirngibl R, Cado D, Shago M, Giguère V (1991) Expression of a retinoic acid response element-hsplacZ transgene defines specific domains of transcriptional activity during mouse embryogenesis. Genes Dev 5: 1333-1344</a> <a name="_ENREF_13">Shannon SR, Moise AR, Trainor PA (2017) New insights and changing paradigms in the regulation of vitamin A metabolism in development. Wiley Interdiscip Rev Dev Biol 6: 10.1002/wdev.1264</a> <a name="_ENREF_14">Solomin L, Johansson CB, Zetterström RH, Bissonnette RP, Heyman RA, Olson L, Lendahl U, Frisén J, Perlmann T (1998) Retinoid-X receptor signalling in the developing spinal cord. Nature 395: 398-402</a> <a name="_ENREF_15">Stevison F, Hogarth CA, Tripathy S, Kent T, Isoherranen N (2017) Inhibition of the all-trans Retinoic Acid ( at RA) Hydroxylases CYP26A1 and CYP26B1 Results in Dynamic, Tissue-Specific Changes in Endogenous at RA Signaling. Drug Metab Dispos 45</a> <a name="_ENREF_16">Stoppie P, Borgers M, Borghgraef P, Dillen L, Goossens J, Sanz G, Szel G, Van Hove C, Van Nyen G, Nobels G, Vanden Bossche H, Venet M, Willemsens G, Van Wauwe J (2000) R115866 inhibits all-trans-retinoic acid metabolism and exerts retinoidal effects in rodents. J Pharmacol Exp Ther 293: 304-312</a> <a name="_ENREF_17">Topletz AR, Tripathy S, Foti RS, Shimshoni JA, Nelson WL, Isoherranen N (2015) Induction of CYP26A1 by metabolites of retinoic acid: evidence that CYP26A1 is an important enzyme in the elimination of active retinoids. Mol Pharmacol 87: 430-441</a> AOPWiki 2021-05-29T11:55:01

2021-11-11T15:07:57

Increased premature meiotic initiation in fetal male germ cells

premature meiosis, male germ cells

Cellular

There are no OECD validated assays for measuring meiotic initiation. Meiotic factors, such as Stra8, Sycp3, gH2AX mRNA and protein levels can be measured using various probes and antibodies that are commercially available eg. (<a href="#_ENREF_2" title="Bowles, 2006 #3">Bowles et al, 2006</a>). Indirect measurements in animal models can be performed using the Stra8 promoter element driving expression of reporter protein GFP (<a href="#_ENREF_3" title="Feng, 2021 #69">Feng et al, 2021</a>). This reporter assay can detect the presence (GFP) or absence (GFP negative) of Stra8 induction in a semi-quantitative manner.

Fetal male germ cells must enter cell cycle quiescence (G0/G1 arrest) during fetal life and premature meiosis in gonocytes leads to their removal/death (<a href="#_ENREF_10" title="Spiller, 2017 #47">Spiller et al, 2017</a>). This process is conserved between mice, rats and humans.

High Male

Moderate

Foetal

Not Specified High <a name="_ENREF_1">Bowles J, Feng CW, Spiller CM, Davidson TL, Jackson A, Koopman P (2010) FGF9 suppresses meiosis and promotes male germ cell fate in mice. Dev Cell 19: 440-449</a> <a name="_ENREF_2">Bowles J, Knight D, Smith C, Wilhelm D, Richman J, Mamiya S, Yashiro K, Chawengsaksophak K, Wilson MJ, Rossant J, Hamada H, Koopman P (2006) Retinoid signaling determines germ cell fate in mice. Science 312: 596-600</a> <a name="_ENREF_3">Feng CW, Burnet G, Spiller CM, Cheung FKM, Chawengsaksophak K, Koopman P, Bowles J (2021) Identification of regulatory elements required for Stra8 expression in fetal ovarian germ cells of the mouse. Development 148: dev194977</a> <a name="_ENREF_4">Jørgensen A, Nielsen JE, Perlman S, Lundvall L, Mitchell RT, Juul A, Rajpert-De Meyts E (2015) Ex vivo culture of human fetal gonads: manipulation of meiosis signalling by retinoic acid treatment disrupts testis development. Hum Reprod 30: 2351-2363</a> <a name="_ENREF_5">Koubova J, Menke DB, Zhou Q, Capel B, Griswold MD, Page DC (2006) Retinoic acid regulates sex-specific timing of meiotic initiation in mice. Proc Natl Acad Sci U S A 103: 2474-2479</a> <a name="_ENREF_6">MacLean G, Li H, Metzger D, Chambon P, Petkovich M (2007) Apoptotic extinction of germ cells in testes of Cyp26b1 knockout mice. Endocrinology 148: 4560-4567</a> <a name="_ENREF_7">McCarrey JR (2013) Toward a more precise and informative nomenclature describing fetal and neonatal male germ cells in rodents. Biol Reprod 89: 47</a> <a name="_ENREF_8">McLaren A (1984) Meiosis and differentiation of mouse germ cells. Symp Soc Exp Biol 38: 7-23</a> <a name="_ENREF_9">Spiller C, Bowles J (2019) Sexually dimorphic germ cell identity in mammals. Curr Top Dev Biol 134: 252-288</a> <a name="_ENREF_10">Spiller C, Koopman P, Bowles J (2017) Sex Determination in the Mammalian Germline. Annu Rev Genet 51: 265-285</a> <a name="_ENREF_11">Trautmann E, Guerquin MJ, Duquenne C, Lahaye JB, Habert R, Livera G (2008) Retinoic acid prevents germ cell mitotic arrest in mouse fetal testes. Cell Cycle 7: 656-664</a> AOPWiki 2021-05-29T12:12:05

2026-04-24T03:56:03

Decrease (loss of) fetal male germ cells

Germ cell loss, male

Cellular

Apoptosis is most routinely detected by DNA ladder assay, TUNEL assay or Comet assay (<a href="#_ENREF_11" title="Majtnerová, 2018 #93">Majtnerová & Rou&scaron;ar, 2018</a>). Terminal deoxynucleotidyl transferase dUTP nick end labeling (TUNEL) assay, which detects apoptotic DNA fragmentations (<a href="#_ENREF_6" title="Gorczyca, 1992 #92">Gorczyca et al, 1992</a>) is available commercially from numerous companies using various staining technologies. DNA laddering can be used to measure apoptosis at later stages only and is used to detect apoptosis of many cells, as it involves separation of DNA by agarose gel electrophoresis (<a href="#_ENREF_5" title="Gong, 1994 #94">Gong et al, 1994</a>).  Comet assay, or single cell gel electrophoresis assay, can detect DNA damage at single-cell resolution (<a href="#_ENREF_20" title="Singh, 1988 #96">Singh et al, 1988</a>). The alkaline Comet Assay is part of OECD Test Guideline 489 (<a href="#_ENREF_15" title="OECD, 2016 #95">OECD, 2016</a>). Direct measurements of total germ cell number in animal models can be performed with using various probes and antibodies to germ cell markers that are commercially available and reporter assays using germ cell specific promoter elements driving expression of reporter proteins. These reporter assays can detect the presence of germ cells in a quantitative manner. Examples include reporter mouse line OG2 (<a href="#_ENREF_21" title="Szabó, 2002 #100">Szabó et al, 2002</a>).

Fetal male germ cells must enter cell cycle quiescence during fetal life (<a href="#_ENREF_13" title="McLaren, 2001 #102">McLaren, 2001</a>). This process is conserved between mice, rats and humans (<a href="#_ENREF_4" title="Francavilla, 1990 #101">Francavilla et al, 1990</a>)

High Male

High

Fetal

Moderate <a name="_ENREF_1">Aitken RJ, Findlay JK, Hutt KJ, Kerr JB (2011) Apoptosis in the germ line. Reproduction 141: 139-150</a> <a name="_ENREF_2">Coucouvanis EC, Sherwood SW, Carswell-Crumpton C, Spack EG, Jones PP (1993) Evidence that the mechanism of prenatal germ cell death in the mouse is apoptosis. Exp Cell Res 209: 238-247</a> <a name="_ENREF_3">Cupp AS, Dufour JM, Kim G, Skinner MK, Kim KH (1999) Action of retinoids on embryonic and early postnatal testis development. Endocrinology 140: 2343-2352</a> <a name="_ENREF_4">Francavilla S, Cordeschi G, Properzi G, Concordia N, Cappa F, Pozzi V (1990) Ultrastructure of fetal human gonad before sexual differentiation and during early testicular and ovarian development. J Submicrosc Cytol Pathol 22: 389-400</a> <a name="_ENREF_5">Gong J, Traganos F, Darzynkiewicz Z (1994) A selective procedure for DNA extraction from apoptotic cells applicable for gel electrophoresis and flow cytometry. Anal Biochem 218: 314-319</a> <a name="_ENREF_6">Gorczyca W, Bruno S, Darzynkiewicz R, Gong J, Darzynkiewicz Z (1992) DNA strand breaks occurring during apoptosis - their early insitu detection by the terminal deoxynucleotidyl transferase and nick translation assays and prevention by serine protease inhibitors. Int J Oncol 1: 639-648</a> <a name="_ENREF_7">Jørgensen A, Nielsen JE, Perlman S, Lundvall L, Mitchell RT, Juul A, Rajpert-De Meyts E (2015) Ex vivo culture of human fetal gonads: manipulation of meiosis signalling by retinoic acid treatment disrupts testis development. Hum Reprod 30: 2351-2363</a> <a name="_ENREF_8">Knudson CM, Tung KS, Tourtellotte WG, Brown GA, Korsmeyer SJ (1995) Bax-deficient mice with lymphoid hyperplasia and male germ cell death. Science 270: 96-99</a> <a name="_ENREF_9">Livera G, Rouiller-Fabre V, Durand P, Habert R (2000) Multiple effects of retinoids on the development of Sertoli, germ, and Leydig cells of fetal and neonatal rat testis in culture. Biol Reprod 62: 1303-1314</a> <a name="_ENREF_10">MacLean G, Li H, Metzger D, Chambon P, Petkovich M (2007) Apoptotic extinction of germ cells in testes of Cyp26b1 knockout mice. Endocrinology 148: 4560-4567</a> <a name="_ENREF_11">Majtnerová P, Rou&scaron;ar T (2018) An overview of apoptosis assays detecting DNA fragmentation. Mol Biol Rep 45: 1469-1478</a> <a name="_ENREF_12">Marinos E, Kulukussa M, Zotos A, Kittas C (1995) Retinoic acid affects basement membrane formation of the seminiferous cords in 14-day male rat gonads in vitro. Differentiation 59: 87-94</a> <a name="_ENREF_13">McLaren A (2001) Mammalian germ cells: birth, sex, and immortality. Cell Struct Funct 26: 119-122</a> <a name="_ENREF_14">Nguyen DH, Soygur B, Peng SP, Malki S, Hu G, Laird DJ (2020) Apoptosis in the fetal testis eliminates developmentally defective germ cell clones. Nat Cell Biol 22: 1423-1435</a> <a name="_ENREF_15">OECD. (2016) Test No. 489: In Vivo Mammalian Alkaline Comet Assay. OECD Guidelines for the Testing of Chemicals, Section 4. OECD Publishing, Paris.</a> <a name="_ENREF_16">Rahban R, Nef S (2020) Regional difference in semen quality of young men: a review on the implication of environmental and lifestyle factors during fetal life and adulthood. Basic Clin Androl 30: 16</a> <a name="_ENREF_17">Rodriguez I, Ody C, Araki K, Garcia I, Vassalli P (1997) An early and massive wave of germinal cell apoptosis is required for the development of functional spermatogenesis. EMBO J 16: 2262-2270</a> <a name="_ENREF_18">Rucker 3rd EB, Dierisseau P, Wagner KU, Garrett L, Wynshaw-Boris A, Flaws JA, Hennighausen L (2000) Bcl-x and Bax regulate mouse primordial germ cell survival and apoptosis during embryogenesis. Mol Endocrinol 14: 1038-1052</a> <a name="_ENREF_19">Ryu JY, Whang J, Park H, Im JY, Kim J, Ahn MY, Lee J, Kim HS, Lee BM, Yoo SD, Kwack SJ, Oh JH, Park KL, Han SY, Kim SH (2007) Di(2-ethylhexyl) phthalate induces apoptosis through peroxisome proliferators-activated receptor-gamma and ERK 1/2 activation in testis of Sprague-Dawley rats. J Toxicol Environ Health A 70: 1296-1303</a> <a name="_ENREF_20">Singh NP, McCoy MT, Tice RR, Schneider EL (1988) A simple technique for quantitation of low levels of DNA damage in individual cells. Exp Cell Res 175: 184-191</a> <a name="_ENREF_21">Szabó PE, Hübner K, Schöler H, Mann JR (2002) Allele-specific expression of imprinted genes in mouse migratory primordial germ cells. Mech Dev 115: 157-160</a> <a name="_ENREF_22">Trautmann E, Guerquin MJ, Duquenne C, Lahaye JB, Habert R, Livera G (2008) Retinoic acid prevents germ cell mitotic arrest in mouse fetal testes. Cell Cycle 7: 656-664</a> <a name="_ENREF_23">Wang C, Cui YG, Wang XH, Jia Y, Hikim AS, Lue YH, Tong JS, Qian LX, Sha JH, Zhou ZM, Hull L, Leung A, Swerdloff RS (2007) transient scrotal hyperthermia and levonorgestrel enhance testosterone-induced spermatogenesis suppression in men through increased germ cell apoptosis. J Clin Endocrinol Metab 92: 3292-3304</a> <a name="_ENREF_24">Wang RA, Nakane PK, Koji T (1998) Autonomous cell death of mouse male germ cells during fetal and postnatal period. Biol Reprod 58: 1250-1256</a> <a name="_ENREF_25">Working PK (1988) Male reproductive toxicology: comparison of the human to animal models. Environ Health Perspect 77: 37-44</a> AOPWiki 2021-05-29T12:15:11

2021-11-11T15:17:53

Reduce, Sperm count

Individual

AOPWiki 2020-04-06T09:49:03

2020-04-06T11:40:28

Inhibition of CYP26B1 activity

CYP26B1, inhibition

Molecular

CYP26B1 and its function Numerous physiological processes as well as fetal development is dependent on correct levels of retinoic acid (RA). RA homeostasis is tightly regulated and involves, amongst many other factors, breakdown by the Cytochrome P450 enzymes of family 26 (<a href="#_ENREF_7" title="Kedishvili, 2013 #35">Kedishvili, 2013</a>; <a href="#_ENREF_19" title="White, 1997 #335">White et al, 1997</a>; <a href="#_ENREF_20" title="White, 1996 #336">White et al, 1996</a>). The family consists of the enzymes CYP26A1, CYP26B1, and CYP26C1 (<a href="#_ENREF_6" title="Isoherranen, 2019 #34">Isoherranen & Zhong, 2019</a>). These RA-metabolizing enzymes convert all-trans-RA to more polar metabolites, including 4-hydroxy-RA and 4-oxo-RA (<a href="#_ENREF_20" title="White, 1996 #336">White et al, 1996</a>; <a href="#_ENREF_21" title="White, 2000 #337">White et al, 2000</a>). CYP26B1 is particularly important for the clearance of RA in the fetal mouse testis, with knockout models having established its critical role in normal testis development in preventing premature meiotic initiation of male germ cells (<a href="#_ENREF_2" title="Bowles, 2018 #4">Bowles et al, 2018</a>; <a href="#_ENREF_3" title="Bowles, 2006 #3">Bowles et al, 2006</a>; <a href="#_ENREF_9" title="Li, 2009 #327">Li et al, 2009</a>; <a href="#_ENREF_11" title="MacLean, 2007 #26">MacLean et al, 2007</a>). CYP26B1 is necessary for steroidogenesis and male reproductive tract formation (<a href="#_ENREF_2" title="Bowles, 2018 #4">Bowles et al, 2018</a>), and may also play a role in maintaining normal spermatogenesis in the adult male mouse (<a href="#_ENREF_5" title="Hogarth, 2015 #75">Hogarth et al, 2015</a>). CYP26B1 has been shown to be expressed in the postnatal mouse ovary, where it is proposed to regulate granulosa cell proliferation (<a href="#_ENREF_8" title="Kipp, 2011 #326">Kipp et al, 2011</a>). In addition to reproductive development, CYP26B1 is important for other aspects of embryonic development. The expression of CYP26B1 is initiated at embryonic day 8 in the mouse hindbrain and is expressed in the limb buds from the beginning of their outgrowth as well as later in many different tissues during organ development including the genital tubercle, craniofacial areas, and spinal cord (<a href="#_ENREF_1" title="Abu-Abed, 2002 #323">Abu-Abed et al, 2002</a>; <a href="#_ENREF_10" title="MacLean, 2001 #328">MacLean et al, 2001</a>; <a href="#_ENREF_13" title="Ross, 2011 #203">Ross & Zolfaghari, 2011</a>). Consistent with this, Cyp26b1-knockout mice display various developmental defects including severe limb malformations and pups born alive die right after birth due to respiratory distress (<a href="#_ENREF_22" title="Yashiro, 2004 #338">Yashiro et al, 2004</a>).  Besides from the important role CYP26B1 plays during fetal development, CYP26B1 is also expressed in multiple tissues in the adult human including adipose tissue, bladder, blood vessels, brain, kidney, adrenals, liver, lung, pancreas, intestines, testis, uterus, and skin (<a href="#_ENREF_15" title="The-Human-Protein-Atlas, 2021 #331">The-Human-Protein-Atlas, 2021</a>; <a href="#_ENREF_17" title="Topletz, 2012 #333">Topletz et al, 2012</a>).   CYP26B1 inhibition as Key Event The main function of CYP26B1 is to inactivate all-trans RA. The major primary metabolites formed from RA by CYP26B1 are 4-OH-RA and 18-OH-RA (<a href="#_ENREF_17" title="Topletz, 2012 #333">Topletz et al, 2012</a>) and CYP26B1 shows preference for the following substrates: all-trans-RA > 9-cis-RA > 13-cis-RA (<a href="#_ENREF_17" title="Topletz, 2012 #333">Topletz et al, 2012</a>; <a href="#_ENREF_21" title="White, 2000 #337">White et al, 2000</a>). CYP26B1 is regulated by a range of molecular factors but also by RA itself (<a href="#_ENREF_6" title="Isoherranen, 2019 #34">Isoherranen & Zhong, 2019</a>; <a href="#_ENREF_21" title="White, 2000 #337">White et al, 2000</a>).

CYP26B1 is highly evolutionary conserved with e.g. a human to mouse sequence homology of 93% (<a href="#_ENREF_14" title="Thatcher, 2009 #330">Thatcher & Isoherranen, 2009</a>). This KE is applicable for both sexes, across developmental stages into adulthood, in numerous cells and tissues and across taxa.

High Male High Female

Moderate

All life stages

Moderate <a name="_ENREF_1">Abu-Abed S, MacLean G, Fraulob V, Chambon P, Petkovich M, Dollé P (2002) Differential expression of the retinoic acid-metabolizing enzymes CYP26A1 and CYP26B1 during murine organogenesis. Mech Dev 110: 173-177</a> <a name="_ENREF_2">Bowles J, Feng CW, Inseson J, Miles K, Spiller CM, Harley VR, Sinclair AH, Koopman P (2018) Retinoic Acid Antagonizes Testis Development in Mice. Cell Rep 24: 1330-1341</a> <a name="_ENREF_3">Bowles J, Knight D, Smith C, Wilhelm D, Richman J, Mamiya S, Yashiro K, Chawengsaksophak K, Wilson MJ, Rossant J, Hamada H, Koopman P (2006) Retinoid signaling determines germ cell fate in mice. Science 312: 596-600</a> <a name="_ENREF_4">Foti RS, Diaz P, Douguet D (2016) Comparison of the ligand binding site of CYP2C8 with CYP26A1 and CYP26B1: a structural basis for the identification of new inhibitors of the retinoic acid hydroxylases. J Enzyme Inhib Med Chem 31: 148-161</a> <a name="_ENREF_5">Hogarth CA, Evans E, Onken J, Kent T, D. M, Petkovich M, Griswold MD (2015) CYP26 Enzymes Are Necessary Within the Postnatal Seminiferous Epithelium for Normal Murine Spermatogenesis. Biol Reprod 93: 19</a> <a name="_ENREF_6">Isoherranen N, Zhong G (2019) Biochemical and physiological importance of the CYP26 retinoic acid hydroxylases. Pharmacol Ther 204: 107400</a> <a name="_ENREF_7">Kedishvili NY (2013) Enzymology of retinoic acid biosynthesis and degradation. J Lipid Res 54: 1744-1760</a> <a name="_ENREF_8">Kipp JL, Golebiowski A, Rodriguez G, Demczuk M, Kilen SM, Mayo KE (2011) Gene expression profiling reveals Cyp26b1 to be an activin regulated gene involved in ovarian granulosa cell proliferation. Endocrinology 152: 303-312</a> <a name="_ENREF_9">Li H, MacLean G, Cameron D, Clagett-Dame M, Petkovich M (2009) Cyp26b1 expression in murine Sertoli cells is required to maintain male germ cells in an undifferentiated state during embryogenesis. PLoS One 4: e7501</a> <a name="_ENREF_10">MacLean G, Abu-Abed S, Dollé P, Tahayato A, Chambon P, Petkovich M (2001) Cloning of a novel retinoic-acid metabolizing cytochrome P450, Cyp26B1, and comparative expression analysis with Cyp26A1 during early murine development. Mech Dev 107: 195-201</a> <a name="_ENREF_11">MacLean G, Li H, Metzger D, Chambon P, Petkovich M (2007) Apoptotic extinction of germ cells in testes of Cyp26b1 knockout mice. Endocrinology 148: 4560-4567</a> <a name="_ENREF_12">Nelson CH, Buttrick BR, Isoherranen N (2013) Therapeutic potential of the inhibition of the retinoic acid hydroxylases CYP26A1 and CYP26B1 by xenobiotics. Curr Top Med Chem 13: 1402-1428</a> <a name="_ENREF_13">Ross AC, Zolfaghari R (2011) Cytochrome P450s in the regulation of cellular retinoic acid metabolism. Annu Rev Nutr 31: 65-87</a> <a name="_ENREF_14">Thatcher JE, Isoherranen N (2009) The role of CYP26 enzymes in retinoic acid clearance. Expert Opin Drug Metab Toxicol 5: 875-886</a> <a name="_ENREF_15">The-Human-Protein-Atlas. (2021) Tissue expression of CYP26B1.</a> <a name="_ENREF_16">Tiboni GM, Marotta F, Carletti E (2009) Fluconazole alters CYP26 gene expression in mouse embryos. Reprod Toxicol 27: 199-202</a> <a name="_ENREF_17">Topletz AR, Thatcher JE, Zelter A, Lutz JD, Tay S, Nelson WL, Isoherranen N (2012) Comparison of the function and expression of CYP26A1 and CYP26B1, the two retinoic acid hydroxylases. Biochem Pharmacol 83: 149-163</a> <a name="_ENREF_18">Van Wauwe JP, Coene MC, Goossens J, Van Nijen G, Lauwers W (1988) Ketoconazole inhibits the in vitro and in vivo metabolism of all-trans-retinoic acid. J Pharmacol Exp Ther 245: 718-722</a> <a name="_ENREF_19">White JA, Beckett-Jones B, Guo YD, Dilworth FJ, Bonasoro J, Jones G, Petkovich M (1997) cDNA cloning of human retinoic acid-metabolizing enzyme (hP450RAI) identifies a novel family of cytochromes P450. J Biol Chem 272: 18538-18541</a> <a name="_ENREF_20">White JA, Guo YD, Baetz K, Beckett-Jones B, Bonasoro J, Hsu KE, Dilworth FJ, Jones G, Petkovich M (1996) Identification of the retinoic acid-inducible all-trans-retinoic acid 4-hydroxylase. J Biol Chem 271: 29922-29927</a> <a name="_ENREF_21">White JA, Ramshaw H, Taimi M, Stangle W, Zhang A, Everingham S, Creighton S, Tam SP, Jones G, Petkovich M (2000) Identification of the human cytochrome P450, P450RAI-2, which is predominantly expressed in the adult cerebellum and is responsible for all-trans-retinoic acid metabolism. Proc Natl Acad Sci U S A 97: 6403-6408</a> <a name="_ENREF_22">Yashiro K, Zhao X, Uehara M, Yamashita K, Nishijima M, Nishino J, Saijoh Y, Sakai Y, Hamada H (2004) Regulation of retinoic acid distribution is required for proximodistal patterning and outgrowth of the developing mouse limb. Dev Cell 6: 411-422</a> AOPWiki 2021-05-28T09:44:43

2021-11-11T15:00:11

decreased, Fertility

Individual

Biological state capability to produce offspring Biological compartments System General role in biology Fertility is the capacity to conceive or induce conception. Impairment of fertility represents disorders of male or female reproductive functions or capacity.

As a measure, fertility rate, is the number of offspring born per mating pair, individual or population.

Plausible domain of applicability Taxonomic applicability: The impaired fertility may also have relevance for fish, mammals, amphibians, reptiles, birds and and invertebrates with sexual reproduction. Life stage applicability: The impaired fertility can be measured at juveniles and adults. Sex applicability: The impaired fertility can be measured in both male and female species.

High Male High Female

High

Adult, reproductively mature

High

Juvenile

High

Adults

High High High

OECD (2001), Test No. 416: Two-Generation Reproduction Toxicity, OECD Guidelines for the Testing of Chemicals, Section 4, OECD Publishing, Paris, <a href="https://doi.org/10.1787/9789264070868-en">https://doi.org/10.1787/9789264070868-en</a>. OECD (2018), Test No. 443: Extended One-Generation Reproductive Toxicity Study, OECD Guidelines for the Testing of Chemicals, Section 4, OECD Publishing, Paris, <a href="https://doi.org/10.1787/9789264185371-en">https://doi.org/10.1787/9789264185371-en</a>. OECD (2018), Test No. 414: Prenatal Developmental Toxicity Study, OECD Guidelines for the Testing of Chemicals, Section 4, OECD Publishing, Paris, <a href="https://doi.org/10.1787/9789264070820-en">https://doi.org/10.1787/9789264070820-en</a>. OECD (2018), "Reproduction/Developmental Toxicity Screening Test (OECD TG 421) and Combined Repeated Dose Toxicity Study with the Reproduction/Developmental Toxicity Screening Test (OECD TG 422)", in Revised Guidance Document 150 on Standardised Test Guidelines for Evaluating Chemicals for Endocrine Disruption, OECD Publishing, Paris, <a href="https://doi.org/10.1787/9789264304741-25-en">https://doi.org/10.1787/9789264304741-25-en</a>. AOPWiki 2016-11-29T18:41:24

2024-12-17T15:46:15

Increased, Retinoic Acid Receptor Activation

Increased, RAR activation

Tissue

This KE refers to increased activation of the retinoic acid receptor (RAR) occurring in complex biological systems in vivo, such as tissues and organs. Thus, increased activation of RAR is here distinguished from direct agonism of the RAR and from increased (or ectopic) availability or synthesis of its endogenous ligand, all‑trans retinoic acid (atRA). Instead, it may occur downstream of these events. This KE occurs in tissues and organs in vivo, and it is not a tissue‑specific event. RARs are ligand-activated receptors regulated by retinoid ligands, particularly atRA. They mediate several crucial biological processes (e.g., morphogenesis, cell growth regulation, apoptosis, homeostasis etc.). Perturbations of RAR signaling are associated with adverse developmental and physiological outcomes. RARs are members of the nuclear hormone receptor superfamily. There are three major subtypes: RARα, RARβ, and RARγ. RARα may be broadly expressed, while RARβ is related to neurogenesis and development of epithelial tissues, and RARγ in bone and cartilage development. There are different isoforms for each subtypes arising from alternative splicing (RARα1-2, RARβ1–4, and RARγ1-2) (<a href="https://www.sciencedirect.com/science/article/abs/pii/S0031699724117036" style="color:#467886; text-decoration:underline">Germain et al, 2006</a>, <a href="https://pubmed.ncbi.nlm.nih.gov/36149754/" style="color:#467886; text-decoration:underline">Petkovich et al, 2022</a>). The canonical signaling mechanism of RARs involves heterodimerization with retinoid X receptors (RXRs), DNA binding to retinoic acid response elements (RAREs), and ligand‑dependent regulation of transcription. RARs heterodimerize with RXRs, with the RAR-RXR complex binding to RAREs in promoters of their target genes. In the absence of ligand, RAR–RXR complexes are often associated with co‑repressor proteins (e.g., NCoR and SMRT), maintaining transcriptional repression. Upon ligand binding with atRA or other retinoids, the RAR–RXR heterodimers undergo conformational changes that promote dissociation of co‑repressors and recruitment of co‑activator proteins (e.g., SRC1-3), leading to chromatin remodeling and transcriptional activation of several target genes (<a href="https://www.sciencedirect.com/science/article/abs/pii/S0031699724117036" style="color:#467886; text-decoration:underline">Germain et al, 2006</a>, <a href="https://pubmed.ncbi.nlm.nih.gov/36149754/" style="color:#467886; text-decoration:underline">Petkovich et al, 2022</a>, <a href="https://pubmed.ncbi.nlm.nih.gov/22318625/" style="color:#467886; text-decoration:underline">Rhinn et al, 2012</a>, <a href="https://pubmed.ncbi.nlm.nih.gov/24962881/" style="color:#467886; text-decoration:underline">Gutierrez et al, 2014</a>). Increased RAR activation can result from direct agonism of RAR or from increased availability of atRA, its main endogenous ligand; for instance by inhibiting CYP26 enzyme activity required for degradation of atRA (<a href="https://pmc.ncbi.nlm.nih.gov/articles/PMC3789243/" style="color:#467886; text-decoration:underline">Ross et al, 2013</a>). RAR agonism can arise from several retinoids that possess higher potency compared to the endogenous ligand. Increased RAR activation can also be caused by increased atRA levels (due to increased synthesis, e.g., CYP26B inhibition) that has been associated with homeostasis imbalances. Both mechanisms increase RAR‑dependent gene expression and disrupt the tightly controlled retinoid‑regulated biological processes (<a href="https://www.sciencedirect.com/science/article/abs/pii/S0031699724117036" style="color:#467886; text-decoration:underline">Germain et al, 2006</a>, <a href="https://pubmed.ncbi.nlm.nih.gov/17906642/" style="color:#467886; text-decoration:underline">Altucci et al, 2007</a>, <a href="https://pubmed.ncbi.nlm.nih.gov/28446509/" style="color:#467886; text-decoration:underline">Stevison et al, 2017</a>, <a href="https://pubmed.ncbi.nlm.nih.gov/23630397/" style="color:#467886; text-decoration:underline">Kedishvili et al, 2013</a>). Non‑canonical RAR signaling mechanisms, independent of direct transcriptional regulation, have been described in some experimental systems. However, their conservation and quantitative contribution to adverse outcomes in vivo remain unclear (<a href="https://pubmed.ncbi.nlm.nih.gov/23440512/" style="color:#467886; text-decoration:underline">Al Tanoury et al 2013</a>). Accordingly, this KE addresses decreased RAR activation via the canonical, transcription‑dependent pathway.

This KE describes increased RAR activation in vivo; however, presently there are no methods available to directly measure this endpoint. Currently, indirect assessment of RAR activation is limited to in vitro RAR and RAR-RXR transactivation assays (<a href="https://www.oecd.org/en/publications/detailed-review-paper-on-the-retinoid-system_4fbb70a9-en.html" style="color:#467886; text-decoration:underline">OECD Detailed Paper Review on Retinoids</a>, <a href="https://www.oecd.org/content/dam/oecd/en/events/2025/09/peer-review-of-the-retinoic-acid-receptor-transactivation-method-validation/validation-report-retinoic-acid-receptor-transactivation-method.pdf" style="color:#467886; text-decoration:underline">Validation report on a RAR transactivation method</a>). AOP developers are encouraged to add new methods to measure RAR activation levels in vivo whenever they become available.

RARs are well-conserved throughout vertebrate evolution, therefore this KE should be considered broadly applicable across vertebrate species. Regarding invertebrates, evidence for the presence of RARs has been reported within chordate phyla, including non-vertebrate chordates. However, multiple invertebrate lineages appear to have lost RAR genes. Although components of RA signaling have been described in some invertebrate species, it remains debated whether they possess a functional RA signaling pathway (<a href="https://pubmed.ncbi.nlm.nih.gov/28446509/" style="color:#467886; text-decoration:underline">Stevison et al, 2017</a>). AOP developers are encouraged to add additional relevant knowledge to expand on the applicability to also include other vertebrates.

Al Tanoury Z, Piskunov A, Rochette-Egly C. Vitamin A and retinoid signaling: genomic and nongenomic effects. J Lipid Res. 2013;54(7):1761-1775. doi:10.1194/jlr.R030833 Altucci L, Leibowitz MD, Ogilvie KM, de Lera AR, Gronemeyer H. RAR and RXR modulation in cancer and metabolic disease. Nat Rev Drug Discov. 2007;6(10):793-810. doi:10.1038/nrd2397 Kedishvili NY. Enzymology of retinoic acid biosynthesis and degradation. J Lipid Res. 2013;54(7):1744-1760. doi:10.1194/jlr.R037028 Germain P, Chambon P, Eichele G, et al. International Union of Pharmacology. LX. Retinoic acid receptors. Pharmacol Rev. 2006;58(4):712-725. doi:10.1124/pr.58.4.4 Gutierrez-Mazariegos J, Schubert M, Laudet V. Evolution of retinoic acid receptors and retinoic acid signaling. Subcell Biochem. 2014;70:55-73. doi:10.1007/978-94-017-9050-5_4 Organisation for Economic Co-operation and Development (OECD). Detailed Review Paper on the Retinoid System. OECD Environment Directorate, Chemicals and Biotechnology Committee; 2021. Accessed April 23, 2026. https://www.oecd.org/en/publications/detailed-review-paper-on-the-retinoid-system_4fbb70a9-en.html Organisation for Economic Co‑operation and Development (OECD). Peer Review of the Retinoic Acid Receptor Transactivation Method Validation: Validation Report. OECD; 2025. Accessed April 23, 2026. https://www.oecd.org/content/dam/oecd/en/events/2025/09/peer-review-of-the-retinoic-acid-receptor-transactivation-method-validation/validation-report-retinoic-acid-receptor-transactivation-method.pdf Petkovich M, Chambon P. Retinoic acid receptors at 35 years. J Mol Endocrinol. 2022;69(4):T13-T24. Published 2022 Oct 11. doi:10.1530/JME-22-0097 Rhinn M, Dollé P. Retinoic acid signalling during development. Development. 2012;139(5):843-858. doi:10.1242/dev.065938 Ross AC, Zolfaghari R. Cytochrome P450s in the regulation of cellular retinoic acid metabolism. Annu Rev Nutr. 2011;31:65-87. doi:10.1146/annurev-nutr-072610-145127 Stevison F, Hogarth C, Tripathy S, Kent T, Isoherranen N. Inhibition of the all-trans Retinoic Acid (atRA) Hydroxylases CYP26A1 and CYP26B1 Results in Dynamic, Tissue-Specific Changes in Endogenous atRA Signaling. Drug Metab Dispos. 2017;45(7):846-854. doi:10.1124/dmd.117.075341 AOPWiki 2026-04-22T04:46:42

2026-04-23T05:19:45

<upstream-id>f5508ac6-c70c-4fb1-87ad-36f79b462370</upstream-id> <downstream-id>6e0bcb3e-37c0-4fd2-841f-cc4da3fb561d</downstream-id>

AOPWiki 2026-04-24T03:47:12

2026-04-24T03:47:12

<upstream-id>6e0bcb3e-37c0-4fd2-841f-cc4da3fb561d</upstream-id> <downstream-id>b3116804-2ca7-4305-af9b-e9a503360641</downstream-id> Germs cells undergo meiotic cell division to produce haploid sperm or eggs from diploid gonocytes or oocytes, respectively. Meiotic entry occurs during fetal life in germ cells of ovaries but postnatally in germ cells of testes (<a href="#_ENREF_22" title="Spiller, 2017 #47">Spiller et al, 2017</a>). During late fetal life, germ cells in testes remain in a state of mitotic quiescence and it isn’t until prior to puberty that they initiate meiotic entry. All-trans retinoic acid (atRA) is suggested to induce meiosis in both males and females at the appropriate life stages. atRA prompts germ cells of the developing ovary to initiate first round of meiosis during fetal life, whereas male germ cells in the developing testis is prevented from entering meiosis until puberty by the effective breakdown of atRA by CYP26 enzymes. In the absence of atRA, fetal male germ cells enter cell cycle quiescence (<a href="#_ENREF_22" title="Spiller, 2017 #47">Spiller et al, 2017</a>). If, however, atRA is ectopically expressed in the fetal testis, premature meiotic initiation is induced in fetal male germ cells, which ultimately disrupts gonocyte development.

The majority of evidence for this KER is derived from rodent studies. Gonad explants are predominantly used for evidence supporting this KER in humans. The overall strength of evidence will be evaluated upon further studies of relevant literature included from the literature search.

In mammalian germ cells, expression of the pre-meiotic marker Stimulated by retinoic acid gene 8 (Stra8) is a critical factor for meiotic onset and progression (<a href="#_ENREF_3" title="Baltus, 2006 #25">Baltus et al, 2006</a>; <a href="#_ENREF_6" title="Bowles, 2006 #3">Bowles et al, 2006</a>; <a href="#_ENREF_9" title="Feng, 2021 #69">Feng et al, 2021</a>; <a href="#_ENREF_12" title="Koubova, 2014 #70">Koubova et al, 2014</a>; <a href="#_ENREF_13" title="Koubova, 2006 #45">Koubova et al, 2006</a>). In male mice lacking Stra8, the germ cells fail to initiate meiosis at puberty (<a href="#_ENREF_1" title="Anderson, 2008 #103">Anderson et al, 2008</a>), which has also been shown to be the case in the fetal female (<a href="#_ENREF_3" title="Baltus, 2006 #25">Baltus et al, 2006</a>) underlining that Stra8 seems to be required for correct meiotic initiation in both sexes. Though the mechanistic details of the spatiotemporal regulation of Stra8 are yet unclear, robust evidence suggests that atRA is a main regulator of Stra8 expression (<a href="#_ENREF_10" title="Griswold, 2012 #105">Griswold et al, 2012</a>). Germ cells from embryos from pregnant vitamin A (the precursor of atRA) deficient rats fail to upregulate Stra8 and enter meiosis (<a href="#_ENREF_15" title="Li, 2009 #123">Li & Clagett-Dame, 2009</a>) and several functional atRA response elements have been identified within the Stra8 promoter (<a href="#_ENREF_9" title="Feng, 2021 #69">Feng et al, 2021</a>). In the fetal male, somatic expression of the cytochrome P450 (CYP) enzyme CYP26B1 ensures atRA degradation, thus avoiding initiation of meiosis (<a href="#_ENREF_5" title="Bowles, 2018 #4">Bowles et al, 2018</a>; <a href="#_ENREF_6" title="Bowles, 2006 #3">Bowles et al, 2006</a>; <a href="#_ENREF_13" title="Koubova, 2006 #45">Koubova et al, 2006</a>; <a href="#_ENREF_16" title="Li, 2009 #327">Li et al, 2009</a>; <a href="#_ENREF_19" title="MacLean, 2007 #26">MacLean et al, 2007</a>). However, if atRA is not cleared effectively, male germ cells will initiate expression of Stra8, and aberrantly enter meiosis (<a href="#_ENREF_6" title="Bowles, 2006 #3">Bowles et al, 2006</a>; <a href="#_ENREF_13" title="Koubova, 2006 #45">Koubova et al, 2006</a>). Genetic deletion of Cyp26b1 in mice increases endogenous atRA levels in the fetal testis and the germ cells abnormally start to express Stra8 and enter meiosis (<a href="#_ENREF_6" title="Bowles, 2006 #3">Bowles et al, 2006</a>; <a href="#_ENREF_19" title="MacLean, 2007 #26">MacLean et al, 2007</a>). Exogenous atRA can stimulate male germ cells to induce Stra8 expression and meiosis in mouse testis explants (<a href="#_ENREF_6" title="Bowles, 2006 #3">Bowles et al, 2006</a>; <a href="#_ENREF_13" title="Koubova, 2006 #45">Koubova et al, 2006</a>; <a href="#_ENREF_23" title="Trautmann, 2008 #76">Trautmann et al, 2008</a>). This effect seems to be conserved in humans, though limited studies are available. A key difference, however, has been the observation that CYP26B1 is expressed at equal or even higher levels in the fetal ovary than in the fetal human testis (<a href="#_ENREF_8" title="Childs, 2011 #28">Childs et al, 2011</a>; <a href="#_ENREF_11" title="Jørgensen, 2012 #97">Jørgensen et al, 2012</a>). This is in contrast to the sexually dimorphic expression patterns observed in fetal rodents. Lastly, in accordance with the above mentioned rodent studies, single cell suspension cultures of human fetal testes showed increased STRA8 expression in response to exogenous atRA, however, no effect was observed on the gene expression of meiosis markers SYCP3 and DMC1 (<a href="#_ENREF_8" title="Childs, 2011 #28">Childs et al, 2011</a>).

Animal models <table cellspacing="0" class="MsoTableGrid" style="border-collapse:collapse; border:none"> <tbody> <tr> <td style="background-color:gray; border-bottom:1px solid black; border-left:1px solid black; border-right:1px solid black; border-top:1px solid black; vertical-align:top; width:200px"> Model </td> <td style="background-color:gray; border-bottom:1px solid black; border-left:none; border-right:1px solid black; border-top:1px solid black; vertical-align:top; width:200px"> Relevant observations </td> <td style="background-color:gray; border-bottom:1px solid black; border-left:none; border-right:1px solid black; border-top:1px solid black; vertical-align:top; width:200px"> Reference </td> </tr> <tr> <td style="border-bottom:1px solid black; border-left:1px solid black; border-right:1px solid black; border-top:none; vertical-align:top; width:200px"> Cyp26b1 knockout mice </td> <td style="border-bottom:1px solid black; border-left:none; border-right:1px solid black; border-top:none; vertical-align:top; width:200px"> Stra8 and Sycp3 are abnormally expressed in the embryonic testes of Cyp26b1 knockout mice, and this is followed by a loss of male germ cells </td> <td style="border-bottom:1px solid black; border-left:none; border-right:1px solid black; border-top:none; vertical-align:top; width:200px"> (<a href="#_ENREF_19" title="MacLean, 2007 #26">MacLean et al, 2007</a>) </td> </tr> <tr> <td style="border-bottom:1px solid black; border-left:1px solid black; border-right:1px solid black; border-top:none; vertical-align:top; width:200px"> Cyp26b1 knockout mice </td> <td style="border-bottom:1px solid black; border-left:none; border-right:1px solid black; border-top:none; vertical-align:top; width:200px"> Stra8 and Sycp3 are abnormally expressed in the embryonic testes of Cyp26b1 knockout mice </td> <td style="border-bottom:1px solid black; border-left:none; border-right:1px solid black; border-top:none; vertical-align:top; width:200px"> (<a href="#_ENREF_6" title="Bowles, 2006 #3">Bowles et al, 2006</a>) </td> </tr> </tbody> </table>   In vitro/ex vivo <table cellspacing="0" class="MsoTableGrid" style="border-collapse:collapse; border:none; width:604px"> <tbody> <tr> <td style="background-color:gray; border-bottom:1px solid black; border-left:1px solid black; border-right:1px solid black; border-top:1px solid black; vertical-align:top; width:75px"> Study type </td> <td style="background-color:gray; border-bottom:1px solid black; border-left:none; border-right:1px solid black; border-top:1px solid black; vertical-align:top; width:57px"> Species </td> <td style="background-color:gray; border-bottom:1px solid black; border-left:none; border-right:1px solid black; border-top:1px solid black; vertical-align:top; width:88px"> Compound </td> <td style="background-color:gray; border-bottom:1px solid black; border-left:none; border-right:1px solid black; border-top:1px solid black; vertical-align:top; width:56px"> Effect Dose </td> <td style="background-color:gray; border-bottom:1px solid black; border-left:none; border-right:1px solid black; border-top:1px solid black; vertical-align:top; width:62px"> Duration </td> <td style="background-color:gray; border-bottom:1px solid black; border-left:none; border-right:1px solid black; border-top:1px solid black; vertical-align:top; width:145px"> Results </td> <td style="background-color:gray; border-bottom:1px solid black; border-left:none; border-right:1px solid black; border-top:1px solid black; vertical-align:top; width:121px"> Reference </td> </tr> <tr> <td style="border-bottom:1px solid black; border-left:1px solid black; border-right:1px solid black; border-top:none; vertical-align:top; width:75px"> Embryonic stem cells </td> <td style="border-bottom:1px solid black; border-left:none; border-right:1px solid black; border-top:none; vertical-align:top; width:57px"> Mouse </td> <td style="border-bottom:1px solid black; border-left:none; border-right:1px solid black; border-top:none; vertical-align:top; width:88px"> atRA </td> <td style="border-bottom:1px solid black; border-left:none; border-right:1px solid black; border-top:none; vertical-align:top; width:56px"> 100 nM </td> <td style="border-bottom:1px solid black; border-left:none; border-right:1px solid black; border-top:none; vertical-align:top; width:62px"> 4-10 d </td> <td style="border-bottom:1px solid black; border-left:none; border-right:1px solid black; border-top:none; vertical-align:top; width:145px"> Activates meiosis-related gene network </td> <td style="border-bottom:1px solid black; border-left:none; border-right:1px solid black; border-top:none; vertical-align:top; width:121px"> (<a href="#_ENREF_2" title="Aoki, 2012 #119">Aoki & Takada, 2012</a>) </td> </tr> <tr> <td style="border-bottom:1px solid black; border-left:1px solid black; border-right:1px solid black; border-top:none; vertical-align:top; width:75px"> Fetal testes in culture </td> <td style="border-bottom:1px solid black; border-left:none; border-right:1px solid black; border-top:none; vertical-align:top; width:57px"> Mouse </td> <td style="border-bottom:1px solid black; border-left:none; border-right:1px solid black; border-top:none; vertical-align:top; width:88px"> atRA </td> <td style="border-bottom:1px solid black; border-left:none; border-right:1px solid black; border-top:none; vertical-align:top; width:56px"> 1 µM </td> <td style="border-bottom:1px solid black; border-left:none; border-right:1px solid black; border-top:none; vertical-align:top; width:62px"> 48 h or 72 h </td> <td style="border-bottom:1px solid black; border-left:none; border-right:1px solid black; border-top:none; vertical-align:top; width:145px"> Ectopic expression of meiotic markers (Stra8, Sycp3, Dmc1) and decrease in pluripotency marker Oct4 </td> <td style="border-bottom:1px solid black; border-left:none; border-right:1px solid black; border-top:none; vertical-align:top; width:121px"> (<a href="#_ENREF_6" title="Bowles, 2006 #3">Bowles et al, 2006</a>) </td> </tr> <tr> <td style="border-bottom:1px solid black; border-left:1px solid black; border-right:1px solid black; border-top:none; vertical-align:top; width:75px"> Fetal testes in culture </td> <td style="border-bottom:1px solid black; border-left:none; border-right:1px solid black; border-top:none; vertical-align:top; width:57px"> Mouse </td> <td style="border-bottom:1px solid black; border-left:none; border-right:1px solid black; border-top:none; vertical-align:top; width:88px"> Ketoconazole (Cyp26 inhibitor) </td> <td style="border-bottom:1px solid black; border-left:none; border-right:1px solid black; border-top:none; vertical-align:top; width:56px"> 40 µM </td> <td style="border-bottom:1px solid black; border-left:none; border-right:1px solid black; border-top:none; vertical-align:top; width:62px"> 48 h or 72 h </td> <td style="border-bottom:1px solid black; border-left:none; border-right:1px solid black; border-top:none; vertical-align:top; width:145px"> Ectopic expression of meiotic markers (Stra8, Sycp3, Dmc1) and decrease in pluripotency marker Oct4 </td> <td style="border-bottom:1px solid black; border-left:none; border-right:1px solid black; border-top:none; vertical-align:top; width:121px"> (<a href="#_ENREF_6" title="Bowles, 2006 #3">Bowles et al, 2006</a>) </td> </tr> <tr> <td style="border-bottom:1px solid black; border-left:1px solid black; border-right:1px solid black; border-top:none; vertical-align:top; width:75px"> Fetal testes in culture </td> <td style="border-bottom:1px solid black; border-left:none; border-right:1px solid black; border-top:none; vertical-align:top; width:57px"> Mouse </td> <td style="border-bottom:1px solid black; border-left:none; border-right:1px solid black; border-top:none; vertical-align:top; width:88px"> BMS-194753 (RAR-α agonist) </td> <td style="border-bottom:1px solid black; border-left:none; border-right:1px solid black; border-top:none; vertical-align:top; width:56px"> 0.5 µM </td> <td style="border-bottom:1px solid black; border-left:none; border-right:1px solid black; border-top:none; vertical-align:top; width:62px"> 2 d </td> <td style="border-bottom:1px solid black; border-left:none; border-right:1px solid black; border-top:none; vertical-align:top; width:145px"> Ectopic Stra8 expression </td> <td style="border-bottom:1px solid black; border-left:none; border-right:1px solid black; border-top:none; vertical-align:top; width:121px"> (<a href="#_ENREF_13" title="Koubova, 2006 #45">Koubova et al, 2006</a>) </td> </tr> <tr> <td style="border-bottom:1px solid black; border-left:1px solid black; border-right:1px solid black; border-top:none; vertical-align:top; width:75px"> Fetal testes in culture </td> <td style="border-bottom:1px solid black; border-left:none; border-right:1px solid black; border-top:none; vertical-align:top; width:57px"> Mouse </td> <td style="border-bottom:1px solid black; border-left:none; border-right:1px solid black; border-top:none; vertical-align:top; width:88px"> BMS-213309 (RAR-β agonist) </td> <td style="border-bottom:1px solid black; border-left:none; border-right:1px solid black; border-top:none; vertical-align:top; width:56px"> 0.5 µM </td> <td style="border-bottom:1px solid black; border-left:none; border-right:1px solid black; border-top:none; vertical-align:top; width:62px"> 2 d </td> <td style="border-bottom:1px solid black; border-left:none; border-right:1px solid black; border-top:none; vertical-align:top; width:145px"> Ectopic Stra8 expression </td> <td style="border-bottom:1px solid black; border-left:none; border-right:1px solid black; border-top:none; vertical-align:top; width:121px"> (<a href="#_ENREF_13" title="Koubova, 2006 #45">Koubova et al, 2006</a>) </td> </tr> <tr> <td style="border-bottom:1px solid black; border-left:1px solid black; border-right:1px solid black; border-top:none; vertical-align:top; width:75px"> Fetal testes in culture </td> <td style="border-bottom:1px solid black; border-left:none; border-right:1px solid black; border-top:none; vertical-align:top; width:57px"> Mouse </td> <td style="border-bottom:1px solid black; border-left:none; border-right:1px solid black; border-top:none; vertical-align:top; width:88px"> BMS-270394 (RAR-γ agonist) </td> <td style="border-bottom:1px solid black; border-left:none; border-right:1px solid black; border-top:none; vertical-align:top; width:56px"> 0.5 µM </td> <td style="border-bottom:1px solid black; border-left:none; border-right:1px solid black; border-top:none; vertical-align:top; width:62px"> 2 d </td> <td style="border-bottom:1px solid black; border-left:none; border-right:1px solid black; border-top:none; vertical-align:top; width:145px"> Ectopic Stra8 expression </td> <td style="border-bottom:1px solid black; border-left:none; border-right:1px solid black; border-top:none; vertical-align:top; width:121px"> (<a href="#_ENREF_13" title="Koubova, 2006 #45">Koubova et al, 2006</a>) </td> </tr> <tr> <td style="border-bottom:1px solid black; border-left:1px solid black; border-right:1px solid black; border-top:none; vertical-align:top; width:75px"> Fetal testes in culture </td> <td style="border-bottom:1px solid black; border-left:none; border-right:1px solid black; border-top:none; vertical-align:top; width:57px"> Mouse </td> <td style="border-bottom:1px solid black; border-left:none; border-right:1px solid black; border-top:none; vertical-align:top; width:88px"> atRA </td> <td style="border-bottom:1px solid black; border-left:none; border-right:1px solid black; border-top:none; vertical-align:top; width:56px"> 0.7 µM </td> <td style="border-bottom:1px solid black; border-left:none; border-right:1px solid black; border-top:none; vertical-align:top; width:62px"> 2 d </td> <td style="border-bottom:1px solid black; border-left:none; border-right:1px solid black; border-top:none; vertical-align:top; width:145px"> Ectopic Stra8 expression </td> <td style="border-bottom:1px solid black; border-left:none; border-right:1px solid black; border-top:none; vertical-align:top; width:121px"> (<a href="#_ENREF_13" title="Koubova, 2006 #45">Koubova et al, 2006</a>) </td> </tr> <tr> <td style="border-bottom:1px solid black; border-left:1px solid black; border-right:1px solid black; border-top:none; vertical-align:top; width:75px"> Fetal testes in culture </td> <td style="border-bottom:1px solid black; border-left:none; border-right:1px solid black; border-top:none; vertical-align:top; width:57px"> Mouse </td> <td style="border-bottom:1px solid black; border-left:none; border-right:1px solid black; border-top:none; vertical-align:top; width:88px"> Ketoconazole (Cyp26 inhibitor) </td> <td style="border-bottom:1px solid black; border-left:none; border-right:1px solid black; border-top:none; vertical-align:top; width:56px"> 0.7 µM </td> <td style="border-bottom:1px solid black; border-left:none; border-right:1px solid black; border-top:none; vertical-align:top; width:62px"> 2 d </td> <td style="border-bottom:1px solid black; border-left:none; border-right:1px solid black; border-top:none; vertical-align:top; width:145px"> Ectopic Stra8 expression </td> <td style="border-bottom:1px solid black; border-left:none; border-right:1px solid black; border-top:none; vertical-align:top; width:121px"> (<a href="#_ENREF_13" title="Koubova, 2006 #45">Koubova et al, 2006</a>) </td> </tr> <tr> <td style="border-bottom:1px solid black; border-left:1px solid black; border-right:1px solid black; border-top:none; vertical-align:top; width:75px"> Fetal testes in culture </td> <td style="border-bottom:1px solid black; border-left:none; border-right:1px solid black; border-top:none; vertical-align:top; width:57px"> Mouse </td> <td style="border-bottom:1px solid black; border-left:none; border-right:1px solid black; border-top:none; vertical-align:top; width:88px"> R115866 (Cyp26 inhibitor) </td> <td style="border-bottom:1px solid black; border-left:none; border-right:1px solid black; border-top:none; vertical-align:top; width:56px"> 0.7 µM </td> <td style="border-bottom:1px solid black; border-left:none; border-right:1px solid black; border-top:none; vertical-align:top; width:62px"> 2 d </td> <td style="border-bottom:1px solid black; border-left:none; border-right:1px solid black; border-top:none; vertical-align:top; width:145px"> Ectopic Stra8 expression </td> <td style="border-bottom:1px solid black; border-left:none; border-right:1px solid black; border-top:none; vertical-align:top; width:121px"> (<a href="#_ENREF_13" title="Koubova, 2006 #45">Koubova et al, 2006</a>) </td> </tr> <tr> <td style="border-bottom:1px solid black; border-left:1px solid black; border-right:1px solid black; border-top:none; vertical-align:top; width:75px"> Fetal testes in culture </td> <td style="border-bottom:1px solid black; border-left:none; border-right:1px solid black; border-top:none; vertical-align:top; width:57px"> Rats </td> <td style="border-bottom:1px solid black; border-left:none; border-right:1px solid black; border-top:none; vertical-align:top; width:88px"> atRA </td> <td style="border-bottom:1px solid black; border-left:none; border-right:1px solid black; border-top:none; vertical-align:top; width:56px"> 1 µM and 0.031 µM </td> <td style="border-bottom:1px solid black; border-left:none; border-right:1px solid black; border-top:none; vertical-align:top; width:62px"> 2 or 3 d </td> <td style="border-bottom:1px solid black; border-left:none; border-right:1px solid black; border-top:none; vertical-align:top; width:145px"> Increased apoptosis of germ cells, reduction in total number of germ cells </td> <td style="border-bottom:1px solid black; border-left:none; border-right:1px solid black; border-top:none; vertical-align:top; width:121px"> (<a href="#_ENREF_17" title="Livera, 2000 #78">Livera et al, 2000a</a>) </td> </tr> <tr> <td style="border-bottom:1px solid black; border-left:1px solid black; border-right:1px solid black; border-top:none; vertical-align:top; width:75px"> Culture of fetal testis single cell suspension </td> <td style="border-bottom:1px solid black; border-left:none; border-right:1px solid black; border-top:none; vertical-align:top; width:57px"> Human </td> <td style="border-bottom:1px solid black; border-left:none; border-right:1px solid black; border-top:none; vertical-align:top; width:88px"> atRA </td> <td style="border-bottom:1px solid black; border-left:none; border-right:1px solid black; border-top:none; vertical-align:top; width:56px"> 1 µM </td> <td style="border-bottom:1px solid black; border-left:none; border-right:1px solid black; border-top:none; vertical-align:top; width:62px"> 24 h </td> <td style="border-bottom:1px solid black; border-left:none; border-right:1px solid black; border-top:none; vertical-align:top; width:145px"> Increased STRA8 expression, but had no effect on DMC1 or SYCP3 expression </td> <td style="border-bottom:1px solid black; border-left:none; border-right:1px solid black; border-top:none; vertical-align:top; width:121px"> (<a href="#_ENREF_8" title="Childs, 2011 #28">Childs et al, 2011</a>) </td> </tr> </tbody> </table>

Mouse deletion model for the atRA synthesis enzymes Aldh1a1, Aldh1a2 and Aldh1a3 showed decreased expression of  Stra8 in double (Aldh1a2/3) and triple (Aldh1a1/2/3) knockouts, although ultimately germ cells were observed undergoing meiosis in these ovaries, suggesting redundant role for atRA (<a href="#_ENREF_7" title="Chassot, 2020 #111">Chassot et al, 2020</a>; <a href="#_ENREF_14" title="Kumar, 2011 #121">Kumar et al, 2011</a>). Similarly, transgenic mice lacking the three atRA nuclear receptors (RAR-a, -b, -g) showed reduced levels of Stra8, although ultimately germ cells were observed undergoing meiosis and were capable of producing live offspring (<a href="#_ENREF_24" title="Vernet, 2020 #109">Vernet et al, 2020</a>). Whether or not these models led to impaired fertility (such as sub-fertility) has not been elucidated and the size of their oocyte pools were not determined. Gain of function mouse ovary models for CYP26A1 and CYP26B1 shows that CYP26B1 can prevent oocytes from entering meiosis (as in, failure to induce Stra8 expression), whereas CYP26A1 does not have the same effect despite being a potent atRA degrading enzyme. This suggests that factor(s) in addition to atRA are required for meiosis induction (<a href="#_ENREF_4" title="Bellutti, 2019 #113">Bellutti et al, 2019</a>).

There is a very limited quantitative understanding of this KER other than the knowledge that when germ cells, from either testis or ovary, are cultured in the presence of atRA, at concentrations as low as 10nM, Stra8 expression is rapidly induced (<a href="#_ENREF_21" title="Spiller, 2019 #71">Spiller & Bowles, 2019</a>).

In vitro and ex vivo, it has been conclusively shown that low levels of exogenous atRA can induce germ cells to enter meiosis in mice (<a href="#_ENREF_6" title="Bowles, 2006 #3">Bowles et al, 2006</a>) and rats (<a href="#_ENREF_18" title="Livera, 2000 #124">Livera et al, 2000b</a>) and, similarly, that it is necessary to achieve meiosis in in-vitro-derived oocytes via PGCLCs (<a href="#_ENREF_20" title="Miyauchi, 2017 #195">Miyauchi et al, 2017</a>). Yet, its exact role in vivo is debated. Whilst the relative levels of endogenous atRA produced by the ovary (for any species) remains unknown, similarly, the quantitative relationship between atRA levels and induction of meiosis also remains unclear. As such, the quantitative understanding of how much atRA needs to be reduced to prevent germ cells from entering meiosis in vivo is rated low.

High Male

Moderate

Fetal

High Moderate Low

<a name="_ENREF_1">Anderson EL, Baltus AE, Roepers-Gajadien HL, Hassold TJ, de Rooij DG, van Pelt AMM, Page DC (2008) Stra8 and its inducer, retinoic acid, regulate meiotic initiation in both spermatogenesis and oogenesis in mice. Proc Natl Acad Sci U S A 105: 14976-14980</a> <a name="_ENREF_2">Aoki T, Takada T (2012) Bisphenol A modulates germ cell differentiation and retinoic acid signaling in mouse ES cells. Reprod Toxicol 34: 463-470</a> <a name="_ENREF_3">Baltus AE, Menke DB, Hu YC, Goodheart ML, Carpenter AE, de Rooij DG, Page DC (2006) In germ cells of mouse embryonic ovaries, the decision to enter meiosis precedes premeiotic DNA replication. Nat Genet 38: 1430-1434</a> <a name="_ENREF_4">Bellutti L, Abby E, Tourpin S, Messiaen S, Moison D, Trautmann E, Guerquin MJ, Rouiller-Fabre V, Habert R, Livera G (2019) Divergent Roles of CYP26B1 and Endogenous Retinoic Acid in Mouse Fetal Gonads. Biomolecules 9: 536</a> <a name="_ENREF_5">Bowles J, Feng CW, Inseson J, Miles K, Spiller CM, Harley VR, Sinclair AH, Koopman P (2018) Retinoic Acid Antagonizes Testis Development in Mice. Cell Rep 24: 1330-1341</a> <a name="_ENREF_6">Bowles J, Knight D, Smith C, Wilhelm D, Richman J, Mamiya S, Yashiro K, Chawengsaksophak K, Wilson MJ, Rossant J, Hamada H, Koopman P (2006) Retinoid signaling determines germ cell fate in mice. Science 312: 596-600</a> <a name="_ENREF_7">Chassot AA, Le Rolle M, Jolivet G, Stevant I, Guigonis JM, Da Silva F, Nef S, Pailhoux E, Schedl A, Ghyselinck NB, Chaboissier MC (2020) Retinoic acid synthesis by ALDH1A proteins is dispensable for meiosis initiation in the mouse fetal ovary. Sci Adv 6: eaaz1261</a> <a name="_ENREF_8">Childs AJ, Cowan G, Kinnell HL, Anderson RA, Saunders PTK (2011) Retinoic Acid signalling and the control of meiotic entry in the human fetal gonad. PLoS One 6: e20249</a> <a name="_ENREF_9">Feng CW, Burnet G, Spiller CM, Cheung FKM, Chawengsaksophak K, Koopman P, Bowles J (2021) Identification of regulatory elements required for Stra8 expression in fetal ovarian germ cells of the mouse. Development 148: dev194977</a> <a name="_ENREF_10">Griswold MD, Hogarth CA, Bowles J, Koopman P (2012) Initiating meiosis: the case for retinoic acid. Biol Reprod 86: 35</a> <a name="_ENREF_11">Jørgensen A, Nielsen JE, Blomberg Jensen M, Græm N, Rajpert-De Meyts E (2012) Analysis of meiosis regulators in human gonads: a sexually dimorphic spatio-temporal expression pattern suggests involvement of DMRT1 in meiotic entry. Mol Hum Reprod 18: 523-534</a> <a name="_ENREF_12">Koubova J, Hu YC, Bhattacharyya T, Soh YQS, Gill ME, Goodheart ML, Hogarth CA, Griswold MD, Page DC (2014) Retinoic acid activates two pathways required for meiosis in mice. PLoS Genet 10: e1004541</a> <a name="_ENREF_13">Koubova J, Menke DB, Zhou Q, Capel B, Griswold MD, Page DC (2006) Retinoic acid regulates sex-specific timing of meiotic initiation in mice. Proc Natl Acad Sci U S A 103: 2474-2479</a> <a name="_ENREF_14">Kumar S, Chatzi C, Brade T, Cunningham TJ, Zhao X, Duester G (2011) Sex-specific timing of meiotic initiation is regulated by Cyp26b1 independent of retinoic acid signalling. Nat Commun 2: 151</a> <a name="_ENREF_15">Li H, Clagett-Dame M (2009) Vitamin A deficiency blocks the initiation of meiosis of germ cells in the developing rat ovary in vivo Biol Reprod 81: 996-1001</a> <a name="_ENREF_16">Li H, MacLean G, Cameron D, Clagett-Dame M, Petkovich M (2009) Cyp26b1 expression in murine Sertoli cells is required to maintain male germ cells in an undifferentiated state during embryogenesis. PLoS One 4: e7501</a> <a name="_ENREF_17">Livera G, Rouiller-Fabre V, Durand P, Habert R (2000a) Multiple effects of retinoids on the development of Sertoli, germ, and Leydig cells of fetal and neonatal rat testis in culture. Biol Reprod 62: 1303-1314</a> <a name="_ENREF_18">Livera G, Rouiller-Fabre V, Valla J, Habert R (2000b) Effects of retinoids on the meiosis in the fetal rat ovary in culture. Mol Cell Endocrinol 165: 225-231</a> <a name="_ENREF_19">MacLean G, Li H, Metzger D, Chambon P, Petkovich M (2007) Apoptotic extinction of germ cells in testes of Cyp26b1 knockout mice. Endocrinology 148: 4560-4567</a> <a name="_ENREF_20">Miyauchi H, Ohta H, Nagaoka S, Nakaki F, Sasaki K, Hayashi K, Yabuta Y, Nakamura T, Yamamoto T, Saitou M (2017) Bone morphogenetic protein and retinoic acid synergistically specify female germ-cell fate in mice. EMBO J 36: 3100-3119</a> <a name="_ENREF_21">Spiller C, Bowles J (2019) Sexually dimorphic germ cell identity in mammals. Curr Top Dev Biol 134: 252-288</a> <a name="_ENREF_22">Spiller C, Koopman P, Bowles J (2017) Sex Determination in the Mammalian Germline. Annu Rev Genet 51: 265-285</a> <a name="_ENREF_23">Trautmann E, Guerquin MJ, Duquenne C, Lahaye JB, Habert R, Livera G (2008) Retinoic acid prevents germ cell mitotic arrest in mouse fetal testes. Cell Cycle 7: 656-664</a> <a name="_ENREF_24">Vernet N, Condrea D, Mayere C, Féret B, Klopfenstein M, Magnant W, Alunni V, Teletin M, Souali-Crespo S, Nef S, Mark M, Ghyselinck NB (2020) Meiosis occurs normally in the fetal ovary of mice lacking all retinoic acid receptors. Sci Adv 6: eaaz1139</a> AOPWiki 2021-11-10T03:28:34

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AOPWiki 2026-04-24T03:50:49

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AOPWiki 2026-04-24T03:51:45

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Inhibition of CYP26B1 activity in fetal testis leading to reduced fertility

Inhibition CYP26B1 in fetal testis leads to reduced fertility

Terje Svingen

BY-SA

2.0

Under REACH, information on reproductive toxicity is required for chemicals with an annual production/importation volume of 10 metric tonnes or more. Standard information requirements include a screening study on reproduction toxicity (OECD TG 421/422) at Annex VIII (10-100 t.p.a), a prenatal developmental toxicity study (OECD 414) on a first species at Annex IX (100-1000 t.p.a), and from March 2015 the OECD 443(Extended One-Generation Reproductive Toxicity Study) is reproductive toxicity requirement instead of the two generation reproductive toxicity study (OECD TG 416). If not conducted already at Annex IX, a prenatal developmental toxicity study on a second species at Annex X (≥ 1000 t.p.a.). Under the Biocidal Products Regulation (BPR), information is also required on reproductive toxicity for active substances as part of core data set and additional data set (EU 2012, ECHA 2013). As a core data set, prenatal developmental toxicity study (EU TM B.31) in rabbits as a first species and a two-generation reproduction toxicity study (EU TM B.31) are required. OECD TG 443 (Extended One-Generation Reproductive Toxicity Study) shall be considered as an alternative approach to the multi-generation study.) According to the Classification, Labelling and Packaging (CLP) regulation (EC, 200; Annex I: 3.7.1.1): a) “reproductive toxicity” includes adverse effects on sexual function and fertility in adult males and females, as well as developmental toxicity in the offspring; b) “effects on fertility” includes adverse effects on sexual function and fertility; and c) “developmental toxicity” includes adverse effects on development of the offspring.

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High Male

<div> <table class="table table-bordered table-fullwidth"> <thead> <tr> <th>Modulating Factor (MF)</th> <th>Influence or Outcome</th> <th>KER(s) involved</th> </tr> </thead> <tbody> <tr> <td> </td> <td> </td> <td> </td> </tr> </tbody> </table> </div>

AOPWiki 2021-05-29T12:26:47

2026-05-01T07:46:27