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Relationship: 2127

Title

A descriptive phrase which clearly defines the two KEs being considered and the sequential relationship between them (i.e., which is upstream, and which is downstream). More help

Altered, Transcription of genes by the AR leads to AGD, decreased

Upstream event

The causing Key Event (KE) in a Key Event Relationship (KER). More help

Altered, Transcription of genes by the AR

Downstream event

The responding Key Event (KE) in a Key Event Relationship (KER). More help

AGD, decreased

Key Event Relationship Overview

The utility of AOPs for regulatory application is defined, to a large extent, by the confidence and precision with which they facilitate extrapolation of data measured at low levels of biological organisation to predicted outcomes at higher levels of organisation and the extent to which they can link biological effect measurements to their specific causes.Within the AOP framework, the predictive relationships that facilitate extrapolation are represented by the KERs. Consequently, the overall WoE for an AOP is a reflection in part, of the level of confidence in the underlying series of KERs it encompasses. Therefore, describing the KERs in an AOP involves assembling and organising the types of information and evidence that defines the scientific basis for inferring the probable change in, or state of, a downstream KE from the known or measured state of an upstream KE. More help

AOPs Referencing Relationship

AOP Name	Adjacency	Weight of Evidence	Quantitative Understanding	Point of Contact	Author Status	OECD Status
5α-reductase inhibition leading to short anogenital distance (AGD) in male (mammalian) offspring	non-adjacent	Moderate		Terje Svingen (send email)	Under development: Not open for comment. Do not cite	Under Review
Androgen receptor (AR) antagonism leading to short anogenital distance (AGD) in male (mammalian) offspring	non-adjacent	Moderate		Terje Svingen (send email)	Under development: Not open for comment. Do not cite	Under Review
Decreased testosterone synthesis leading to short anogenital distance (AGD) in male (mammalian) offspring	non-adjacent	Moderate	Low	Terje Svingen (send email)	Under development: Not open for comment. Do not cite	Under Review

Taxonomic Applicability

Latin or common names of a species or broader taxonomic grouping (e.g., class, order, family) that help to define the biological applicability domain of the KER.In general, this will be dictated by the more restrictive of the two KEs being linked together by the KER. More help

Term	Scientific Term	Evidence	Link
human, mouse, rat	human, mouse, rat	High	NCBI

Sex Applicability

An indication of the the relevant sex for this KER. More help

Sex	Evidence
Male	High

Life Stage Applicability

An indication of the the relevant life stage(s) for this KER. More help

Term	Evidence
Fetal to Parturition	High

Key Event Relationship Description

Provides a concise overview of the information given below as well as addressing details that aren’t inherent in the description of the KEs themselves. More help

During male reproductive development, the androgen receptor (AR) regulates gene transcription in target tissues to induce masculinization. Target tissues include the perineum, the tissue located between the anus and the genitals. This tissue is sexually dimorphic, with males developing the levator ani-bulbocavernosus (LABC) muscle complex in response to androgen signaling. The anogenital distance (AGD) is about twice as long in newborn males than in females in many mammals such mice, rats and humans.

A consequence of reduced androgen action during the masculinization programming window in utero, the male AGD will end up being shorter, approaching female AGD when AR signaling is almost blocked. Measuring of the AGD thus serves as a morphometric biomarker for compromised androgen action during fetal life and is used in OECD test guidelines for assessing endocrine disruption.

This KER refers to a tissue-specific alteration in AR-mediated gene transcription during fetal development leading to a decreased AGD in male offspring. It should be noted that the AR‑mediated transcription operates within a broader developmental context, where timing, tissue specificity, and local signaling environments, including patterning mechanisms and morphogen gradients, jointly determine masculinization outcomes such as AGD. While such contextual influences are acknowledged, the KER remains focused on the androgen‑dependent transcriptional component that drives AGD outcomes.

Evidence Collection Strategy

Include a description of the approach for identification and assembly of the evidence base for the KER. For evidence identification, include, for example, a description of the sources and dates of information consulted including expert knowledge, databases searched and associated search terms/strings. Include also a description of study screening criteria and methodology, study quality assessment considerations, the data extraction strategy and links to any repositories/databases of relevant references.Tabular summaries and links to relevant supporting documentation are encouraged, wherever possible. More help

Search in pubmed (14/12-23): (((antiandrogen) OR (androgen receptor) or (AR)) AND ((transcription) OR (transcriptome*) OR (transcriptomics) OR (differentially expressed)) AND ((perineum) OR (anogenital) OR (bulbocavernosus))): 43 hits.

The following inclusion and exclusion criteria were used for screening the titles and abstracts

Inclusion criteria:

Transcriptional data from perineal tissue after anti-androgenic stressor exposure leading to decreased AGD.

Exclusion criteria:

Not in English
Abstracts and other non-full text publications

After screening, two studies were included.

Evidence Supporting this KER

Addresses the scientific evidence supporting KERs in an AOP setting the stage for overall assessment of the AOP. More help

Biological Plausibility

Addresses the biological rationale for a connection between KEupstream and KEdownstream. This field can also incorporate additional mechanistic details that help inform the relationship between KEs, this is useful when it is not practical/pragmatic to represent these details as separate KEs due to the difficulty or relative infrequency with which it is likely to be measured. More help

Sexual differentiation initiates during fetal life when a surge in testosterone induces masculinization of a range of tissues and organs (Welsh et al). Testosterone and the more potent metabolite DHT mediate masculinization via activation of the AR; a nuclear transcription factor. Androgens thus induce masculinization via altered AR gene transcription in target tissues. This includes the perineum (Niel et al 2008; Ipulan et al 2014) which can be measured as the AGD and is approximately twice as long in newborn male rodents and humans compared to female (Schwartz et al 2019a). This is also evident in male AR knockout mice which present with an AGD that is indistinguishable from wildtype female littermates (MacLean et al 2008; Notini et al 2005). This AR knockout model disrupts the second zinc finger required for DNA binding, demonstrating that genomic (DNA-binding-dependent) actions of the AR are essential for normal male AGD development.

Empirical Evidence

Provides specific (citable) evidence that supports the idea of a change in the upstream KE (KEupstream) leading to, or being associated with, a subsequent change in the downstream KE (KEdownstream), assuming the perturbation of KEupstream is sufficient. More help

Current evidence for direct transcriptional changes mediated by AR disruption in the perineum leading to shorter male AGD is limited. Two studies were identified investigating the transcriptional footprint in the perineum after anti-androgen exposure:

Gestational exposure of rats to the 5α-reductase inhibitor finasteride (leading to decreased DHT levels) decreased fetal male AGD with 37% at gestational day (GD) 21. Microarray was used to compare transcriptional profiles between control males, finasteride-exposed males, and control females, revealing a sexually dimorphic transcriptional profile of the perineum, with the profile of finasteride-exposed males being intermediary to the male and female control groups (Schwartz et al 2019b).

Gestational exposure of rats to the AR antagonist triticonazole induced decreased fetal male AGD at GD21 and a differentially expressed set of genes investigated by whole transcriptome sequencing in the perineum at both GD17 and GD21 (Draskau et al 2022).

Uncertainties and Inconsistencies

Addresses inconsistencies or uncertainties in the relationship including the identification of experimental details that may explain apparent deviations from the expected patterns of concordance. More help

Known modulating factors

This table captures specific information on the MF, its properties, how it affects the KER and respective references.1.) What is the modulating factor? Name the factor for which solid evidence exists that it influences this KER. Examples: age, sex, genotype, diet 2.) Details of this modulating factor. Specify which features of this MF are relevant for this KER. Examples: a specific age range or a specific biological age (defined by...); a specific gene mutation or variant, a specific nutrient (deficit or surplus); a sex-specific homone; a certain threshold value (e.g. serum levels of a chemical above...) 3.) Description of how this modulating factor affects this KER. Describe the provable modification of the KER (also quantitatively, if known). Examples: increase or decrease of the magnitude of effect (by a factor of...); change of the time-course of the effect (onset delay by...); alteration of the probability of the effect; increase or decrease of the sensitivity of the downstream effect (by a factor of...) 4.) Provision of supporting scientific evidence for an effect of this MF on this KER. Give a list of references. More help

Quantitative Understanding of the Linkage

Captures information that helps to define how much change in the upstream KE, and/or for how long, is needed to elicit a detectable and defined change in the downstream KE. More help

Response-response Relationship

Provides sources of data that define the response-response relationships between the KEs. More help

Time-scale

Information regarding the approximate time-scale of the changes in KEdownstream relative to changes in KEupstream (i.e., do effects on KEdownstream lag those on KEupstream by seconds, minutes, hours, or days?). More help

Known Feedforward/Feedback loops influencing this KER

Define whether there are known positive or negative feedback mechanisms involved and what is understood about their time-course and homeostatic limits. More help

Domain of Applicability

A free-text section of the KER description that the developers can use to explain their rationale for the taxonomic, life stage, or sex applicability structured terms. More help

Species

This KER applies to humans, mice, and rats based on biological plausibility. Current empirical evidence is from rat studies only.

Fetal masculinization including the AGD is regulated by androgens interacting with the AR in all mammals, including humans (Murashima et al., 2015; Thankamony et al., 2016), although, the size of the AGD and difference between the sexes vary between species. A large number of studies exist showing that fetal exposure to anti-androgens causes shortened AGD in male rats and mice (Schwartz et al., 2019a). Some epidemiological studies find associations between exposure to anti-androgenic compounds and shorter AGD in boys (Thankamony et al., 2016). However, the associations are not very clear and confidence in the data is limited by conflicting results, possibly due to differences in study design and methods for exposure measurements and analyses. Nevertheless, the KER is considered applicable to humans, based on current understanding of the role of AR activation in fetal masculinization.

Life stage

The length of the AGD is programmed during fetal life during the masculinization programming window. This takes place in rats around embryonic days 15.5-19.5 (GD16-20) and likely gestation weeks 8-14 in humans (Welsh et al., 2008). It should be mentioned that though AGD is believed to be relatively stable throughout life, it can be responsive to postnatal changes in androgen levels (Schwartz et al., 2019a).

Sex

A decrease in the male AGD is a consequence of disrupted androgen action (Welsh et al 2008). While exposure to chemicals during fetal life can also shorten female AGD, the biological significance and the mechanism driving the effect is unknown (Schwartz et al 2019a).

References

List of the literature that was cited for this KER description. More help

Draskau MK, Schwartz CL, Evrard B, Lardenois A, Pask A, Chalmel F and Svingen T (2022). The anti-androgenic fungicide triticonazole induces region-specific transcriptional changes in the developing rat perineum and phallus. Chemosphere 308(Pt 2):136346. doi: 10.1016/j.chemosphere.2022.136346

Ipulan LA, Suzuki K, Sakamoto Y, Murashima A, Imai Y, Omori A, Nakagata N, Nishinakamura R, Valasek P and Yamada G (2014). Nonmyocytic androgen receptor regulates the sexually dimorphic development of the embryonic bulbocavernosus muscle. Endocrinology 155(7):2467-79. doi: 10.1210/en.2014-1008

MacLean HE, Chiu WS, Notini AJ, Axell AM, Davey RA, McManus JF, Ma C, Plant DR, Lynch GS and Zajac JD (2008). Impaired skeletal muscle development and function in male, but not female, genomic androgen receptor knockout mice. FASEB J 22(8):2676-89. doi: 10.1096/fj.08-105726

Murashima, Aki, Satoshi Kishigami, Axel Thomson, and Gen Yamada. “Androgens and Mammalian Male Reproductive Tract Development.” Biochimica et Biophysica Acta (BBA) - Gene Regulatory Mechanisms 1849, no. 2 (February 2015): 163–70. https://doi.org/10.1016/j.bbagrm.2014.05.020.

Niel L, Willemsen KR, Volante SN and Monks DA (2008). Sexual dimorphism and androgen regulation of satellite cell population in differentiating rat levator ani muscle. Dev Neurobiol 68(1):115-22. doi: 10.1002/dneu.20580

Notini AJ, Davey RA, McManus JF, Bate KL and Zajac JD (2005). Genomic actions of the androgen receptor are required for normal male sexual differentiation in a mouse model. J Mol Endocrinol 35(3):547-55. doi: 10.1677/jme.1.0188

Schwartz CL, Christiansen S, Vinggaard AM, Axelstad M, Hass U and Svingen T (2019a). Anogenital distance as a toxicological or clinical marker for fetal androgen action and risk for reproductive disorders. Arch Toxicol 93(2):253-272. doi: 10.1007/s00204-018-2350-5

Schwartz CL, Vinggaard AM, Christiansen S, Darde TA, Chalmel F and Svingen T (2019b). Distinct Transcriptional Profiles of the Female, Male, and Finasteride-Induced Feminized Male Anogenital Region in Rat Fetuses. Toxicol Sci 169(1):303-311. doi: 10.1093/toxsci/kfz046

Thankamony, A., V. Pasterski, K. K. Ong, C. L. Acerini, and I. A. Hughes. “Anogenital Distance as a Marker of Androgen Exposure in Humans.” Andrology 4, no. 4 (July 2016): 616–25. https://doi.org/10.1111/andr.12156.

Welsh M, Saunders PT, Fisken M, Scott HM, Hutchison GR, Smith LB, Sharpe RM. Identification in rats of a programming window for reproductive tract masculinization, disruption of which leads to hypospadias and cryptorchidism. J Clin Invest 118(4):1479-90. doi: 10.1172/JCI34241