API

Relationship: 984

Title

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Activation, AhR leads to Increase, Early Life Stage Mortality

Upstream event

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Activation, AhR

Downstream event

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Increase, Early Life Stage Mortality

Key Event Relationship Overview

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AOPs Referencing Relationship

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Taxonomic Applicability

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Term Scientific Term Evidence Link
chicken Gallus gallus High NCBI
Japanese quail Coturnix japonica High NCBI
Ring-necked pheasant Phasianus colchicus High NCBI
turkey Meleagris gallopavo High NCBI
bobwhite quail Colinus virginianus High NCBI
American kestrel Falco sparverius High NCBI
Double-crested cormorant Double-crested cormorant High NCBI
Eastern bluebird Eastern bluebird High NCBI
zebrafish Danio rerio High NCBI
Fundulus heteroclitus Fundulus heteroclitus High NCBI
Mus musculus Mus musculus High NCBI
Oncorhynchus mykiss Oncorhynchus mykiss Moderate NCBI
Xenopus laevis Xenopus laevis Low NCBI
rat Rattus norvegicus High NCBI

Sex Applicability

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Sex Evidence
Unspecific High

Life Stage Applicability

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Term Evidence
Embryo High
Development High

Key Event Relationship Description

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The aryl hydrocarbon receptor is commonly known for its involvement in xenobiotic metabolism and clearance, but it also regulates a number of endogenous processes including angiogenesis, immune responses, neuronal processes, metabolism, and development of numerous organ systems (Duncan et al., 1998; Emmons et al., 1999; Hahn et al 2002; Lahvis and Bradfield, 1998).  Strong AHR agonists that cause sustained AHR activation interfere with the receptor's endogenous role in embryogenesis, which causes numerous developmental abnormalities and ultimately leads to embryonic death (Kopf and Walker 2009; Carreira et al 2015).

It's important to note that his relationship only applies to AHR agonists that cause sustained AHR activation.  Strong AHR agonists that are rapidly metabolized, such as polycyclic aromatic hydrocarbons, only cause transient AHR activation leading to an alternate mode of toxicity.

This Key Event Relationship describes the indirect link between the Molecular Initiating Event (activation of the AhR) and the Adverse Outcome (increased early life stage mortality).

Evidence Supporting this KER

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Biological Plausibility

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AHR Ligand Binding Domain

  • Mammalian and avian sensitivity to DLCs ultimately comes down to the identity of two particular amino acids in the ligand binding domain (LBD) of the AHR: positions 375 and 319 in mice and 380 and 324 in birds.
    • A 10-fold difference between two strains of mice (non-responsive DBA/2 mouse, and responsive C57BL/6 14 mouse) in CYP1A induction, lethality and teratogenicity following TCDD exposure (Poland et al. 1976), was attributed to  a single nucleotide polymorphism at position 375 (Ema et al. 1994; Poland et al. 1994; Poland and Knutson 1982).
    • Several other studies reported the importance of this amino acid in birds and mammals (Backlund and Ingelman-Sundberg 2004; Ema et al. 1994; Karchner et al. 2006; Murray et al. 2005; Pandini et al. 2007; Pandini et al. 2009; Poland et al. 1994; Ramadoss and Perdew 2004).
  • The amino acid at position 319 plays an important role in ligand-binding affinity to the AHR and transactivation ability of the AHR, due to its involvement in LBD cavity volume and its steric effect (Pandini et al. 2009).
    • Mutation at position 319 in the mouse eliminated AHR DNA binding (Pandini et al. 2009).

Using AHR LBD Constructs to Determine Avian Sensitivity

  • Using chimeric AHR1 constructs combining three AHR1 domains (DBD, LBD and TAD) from the chicken (highly sensitive to DLC toxicity) and common tern (resistant to DLC toxicity), Karchner and colleagues (2006), showed that amino acid differences within the LBD were responsible for differences in TCDD sensitivity between the chicken and common tern.
    • They specifically attributed positions 324 and 380 with differences in TCDD binding affinity and transactivation between the chicken (Ile324_Ser380) and common tern (Val324_Ala380) receptors.
  • The LBD of over 85 bird species have since been analyzed to find that 6 amino acid residues differed among species (Farmahin et al. 2013; Head et al. 2008), but only positions 324 and 380 in the AHR1 LBD were associated with differences in DLC toxicity in ovo and AHR1-mediated gene expression in vitro (Farmahin et al. 2013; Head et al. 2008; Manning et al. 2012).
    • Based on these results, avian species can be divided into one of three AHR1 types based on the amino acids found at positions 324 and 380 of the AHR1 LBD: type 1 (Ile324_Ser380; most sensitive), type 2 (Ile324_Ala380; moderately sensitive) and type 3 (Val324_Ala380; least sensitive) (Farmahin et al. 2013; Head et al. 2008; Manning et al. 2012).
    • A sampling of bird species and their AHR LBD category is described in table 1. A list of 86 species and their subtype can be found in Farmahin et al. (2013).

AHR1 LBD Types.png

Empirical Evidence

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Mammals:

  • AhR deficient strains of mice (Mus musculus) are unaffected by exposure to agonists of the AhR (Fernandez-Salguero et al 1996).
  • Strains of mice that express AhRs with lesser affinity for agonists are more tolerant to adverse effects of exposure relative to strains of mice that express AhRs with greater affinity for agonists (Bisson et al 2009; Ema et al 1993).

Birds:

Binding of dioxin-like compounds (DLCs) to avian AHR1 (Farmahin et al. 2014; Karchner et al. 2006) and AHR1-mediated transactivation measured using luciferase reporter gene (LRG) assays have been demonstrated in domestic and wild species of birds (Farmahin et al. 2012; Farmahin et al. 2013b; Fujisawa et al. 2012; Lee et al. 2009; Manning et al. 2012; Mol et al. 2012), and binding affinity was found to be strongly correlated with embryotoxicity (Manning et al. 2012) .

Fish:

  • Knockdown of the AhR2 prevents mortality following exposure to agonist of the AhR in fishes (Clark et al 2010; Hanno et al 2010; Prasch et al 2003; Van Tiem & Di Giulio 2011). Relative potencies of dioxin-like compounds for activation of AHR2 alpha of rainbow trout (Oncorhynchus mykiss) is predictive of relative potencies for early life stage mortality (Abnet et al 1999).

Amphibians:

  • AhR1s of amphibians studied to date are insensitive to activation by dioxin-like compounds in vitro, while amphibians studies to date are extremely tolerant to adverse effects of exposure to dioxin-like compounds in vivo (Jung et al 1997; Lavine et al 2005; Shoots et al 2015).

Invertebrates:

  • Chemicals that activate the AhR of vertebrates are not known to bind AhRs of invertebrates and increased mortality in invertebrates has never been observed as a result of exposure to these agonists (Hahn 2002; Hahn et al 1994).

Uncertainties and Inconsistencies

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Interestingly, interference with endogenous AHR functions, either by knock-out or by agonist exposure during early development, causes similar cardiac abnormalities (Carreira et al 2015). Although this is counterintuitive, it demonstrates that the AHR has an optimal window of activity, and deviation either above or below this range results in toxicity.

Uncertainites:

  • Only limited AhR activation information is currently available for fishes.
  • Only limited AhR activation information and mortality information is currently available for reptiles and amphibians.
  • Despite decades of research into the molecular initiating event (i.e., binding of chemicals to the AhR) and resulting adverse outcomes (i.e. mortality), less is known about the precise cascade of key events that link activation of the AhR to the adverse outcome (Doering et al 2016).
  • However, hundreds to thousands of different genes are regulated, either directly or indirectly, by activation of the AhR, which presents major uncertainties in the precise pathway of key events or whether perturbation to multiple pathways is the cause of mortality (Brinkmann et al 2016; Doering et al 2016; Huang et al 2014; Li et al 2013; Whitehead et al 2010).
  • Despite these uncertainties in the AOP, considerable research has investigated the indirect relationship between activation of the AhR and increased mortality among different chemicals, species, and taxa (Doering et al 2013).

Inconsistencies:

  • There are no currently known inconsistencies between AhR activation and increased mortality among vertebrates.

Quantitative Understanding of the Linkage

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Birds:

The predictive ability of an LRG assay measuring induction of AHR1-mediated gene expression in cells transfected with different avian AHR1 expression vectors was demonstrated by linear regression analysis comparing log-transformed LD50 values obtained from the literature to log-transformed PC20 values from the LRG assay (Farmahin et al. 2013b; Manning et al. 2012). PC20 values represent the concentration of DLC that elicited 20% of the TCDD maximal response, and were calculated according to the procedure described in OECD guideline 455 (OECD 2009). LD50 values used in regression analyses were obtained from the literature. As shown in the linear regression analysis (Figure 1), logLD50 values were associated with logPC20 and a significant relationship (R2 = 0.93, p < 0.0001) was observed. Thus, to predict the in ovo LD50 for a given species and DLC, one could use the species’ AHR1 LBD sequence to design an AHR1 expression vector, measure the PC20 of the DLC in the LRG assay, and use the regression to obtain an LD50 value.

LRG Linear Regression Avian.jpg

Figure 1. Linear regression analysis comparing LD50 values with PC20 (logLD50 = 0.79logPC20 + 0.51) values derived from luciferase reporter gene (LRG) assay concentration-response curves. Open symbols represent LRG data from wild-type chicken, ring-necked pheasant or Japanese quail AHR1 expression vectors. Closed symbols represent LRG data from mutant AHR1 (Source: Manning, G. E. et al. (2012). Toxicol. Appl. Pharmacol. 263(3), 390-399.)

Mammals:

A quantitative model has been developed linking in silico activation of the AhR with acute lethality (measured as dose to cause 50 % lethality; LD50) among 7 species of mammals with an R2 of 0.99 (Wang et al 2013). The model is described in detail by Wang et al (2013). The model is described as:

If steric (LJ12-6) < 0 then Log (LD50) = 13.273Log(NOQ) + 5.167Log(-Steric(PLP))-0.157Log(-steric(LJ12-6))-1.799Log(-(H-bond))-24.625

If steric (LJ12-6) > 0 then Log (LD50) = 13.273Log(NOQ) + 5.167Log(-Steric(PLP))+0.157Log(-steric(LJ12-6))-1.799Log(-(H-bond))-24.625

Fishes:

Limited information is currently available across fishes. However, a quantitative model has been developed linking in vitro activation of the AhR2 alpha in transfected COS-7 cells (meaured as concentration to cause 50 % effect; EC50) with early life stage mortality (measured as dose to cause 50 % lethality; LD50) for rainbow trout (Oncorhynchus mykiss) across 6 chemicals with an R2 of 0.81 (Abnet et al 1999). The model is described in detail by Abnet et al (1999). The model is described as:

LD50 = 1.57*(EC50)-0.2418

Amphibians and reptiles:

No quantitative models are currently available for amphibians or reptiles.

Response-response Relationship

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Time-scale

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Known modulating factors

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Known Feedforward/Feedback loops influencing this KER

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Domain of Applicability

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  • Overall, this KER is believed to be applicable to all vertebrates based on mortality as a result of exposure to known agonists of the AhR (Buckler et al 2015; Cohen-Barnhouse et al 2011; Elonen et al 1998; Johnson et al 1998; Jung et al 1997; Kopf & Walker 2009; Park et al 2014; Tillitt et al 2016; Toomey et al 2001; Walker et al 1991; Wang et al 2013; Yamauchi et al 2006; Zabel et al 1995).

 

  • The correlation between AHR-mediated reporter gene activity and embryo death has been demonstrated in avian species as described above.
  • Little is known about differences in binding affinity of AhRs and how this relates to sensitivity in non-avian taxa.
  • Low binding affinity for DLCs of AhR1s of African clawed frog (Xenopus laevis) and axolotl (Ambystoma mexicanum) has been suggested as a mechanism for tolerance of these amphibians to DLCs (Lavine et al 2005; Shoots et al 2015).
  • Among reptiles, only AhRs of American alligator (Alligator mississippiensis) have been investigated and little is known about the sensitivity of American alligator or other reptiles to DLCs (Oka et al 2016).
  • Among fishes, great differences in sensitivity to DLCs are known both for AhRs and for embryos among species that have been tested (Doering et al 2013; 2014).
  • Differences in binding affinity of the AhR2 have been demonstrated to explain differences in sensitivity to DLCs between sensitive and tolerant populations of Atlantic Tomcod (Microgadus tomcod) (Wirgin et al 2011).
  • Information is not yet available regarding whether differences in binding affinity of AhRs of fishes are predictive of differences in sensitivity of embryos, juveniles, or adults (Doering et al 2013).

References

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1. Backlund, M., and Ingelman-Sundberg, M. (2004). Different structural requirements of the ligand binding domain of the aryl hydrocarbon receptor for high- and low-affinity ligand binding and receptor activation. Mol. Pharmacol. 65(2), 416-425.

2. Ema, M., Ohe, N., Suzuki, M., Mimura, J., Sogawa, K., Ikawa, S., and Fujii-Kuriyama, Y. (1994). Dioxin binding activities of polymorphic forms of mouse and human arylhydrocarbon receptors. J. Biol. Chem. 269(44), 27337-27343.

3. Farmahin, R., Manning, G. E., Crump, D., Wu, D., Mundy, L. J., Jones, S. P., Hahn, M. E., Karchner, S. I., Giesy, J. P., Bursian, S. J., Zwiernik, M. J., Fredricks, T. B., and Kennedy, S. W. (2013). Amino acid sequence of the ligand-binding domain of the aryl hydrocarbon receptor 1 predicts sensitivity of wild birds to effects of dioxin-like compounds. Toxicol. Sci. 131(1), 139-152.

4. Head, J. A., Hahn, M. E., and Kennedy, S. W. (2008). Key amino acids in the aryl hydrocarbon receptor predict dioxin sensitivity in avian species. Environ. Sci. Technol. 42(19), 7535-7541.

5. Karchner, S. I., Franks, D. G., Kennedy, S. W., and Hahn, M. E. (2006). The molecular basis for differential dioxin sensitivity in birds: Role of the aryl hydrocarbon receptor. Proc. Natl. Acad. Sci. U. S. A 103(16), 6252-6257.

6. Manning, G. E., Farmahin, R., Crump, D., Jones, S. P., Klein, J., Konstantinov, A., Potter, D., and Kennedy, S. W. (2012). A luciferase reporter gene assay and aryl hydrocarbon receptor 1 genotype predict the embryolethality of polychlorinated biphenyls in avian species. Toxicol. Appl. Pharmacol. 263(3), 390-399.

7. Murray, I. A., Reen, R. K., Leathery, N., Ramadoss, P., Bonati, L., Gonzalez, F. J., Peters, J. M., and Perdew, G. H. (2005). Evidence that ligand binding is a key determinant of Ah receptor-mediated transcriptional activity. Arch. Biochem. Biophys. 442(1), 59-71.

8. Pandini, A., Denison, M. S., Song, Y., Soshilov, A. A., and Bonati, L. (2007). Structural and functional characterization of the aryl hydrocarbon receptor ligand binding domain by homology modeling and mutational analysis. Biochemistry 46(3), 696-708.

9. Pandini, A., Soshilov, A. A., Song, Y., Zhao, J., Bonati, L., and Denison, M. S. (2009). Detection of the TCDD binding-fingerprint within the Ah receptor ligand binding domain by structurally driven mutagenesis and functional analysis. Biochemistry 48(25), 5972-5983.

10. Poland, A., Glover, E., and Kende, A. S. (1976). Stereospecific, high affinity binding of 2,3,7,8-tetrachlorodibenzo-p-dioxin by hepatic cytosol. Evidence that the binding species is receptor for induction of aryl hydrocarbon hydroxylase. J. Biol. Chem. 251(16), 4936-4946.

11. Poland, A., and Knutson, J. C. (1982). 2,3,7,8-tetrachlorodibenzo-p-dioxin and related halogenated aromatic hydrocarbons: examination of the mechanism of toxicity. Annu. Rev. Pharmacol. Toxicol. 22, 517-554. 12. Poland, A., Palen, D., and Glover, E. (1994). Analysis of the four alleles of the murine aryl hydrocarbon receptor. Mol. Pharmacol. 46(5), 915-921.

13. Ramadoss, P., and Perdew, G. H. (2004). Use of 2-azido-3-[125I]iodo-7,8-dibromodibenzo-p-dioxin as a probe to determine the relative ligand affinity of human versus mouse aryl hydrocarbon receptor in cultured cells. Mol. Pharmacol. 66(1), 129-136.

14. Farmahin, R., Wu, D., Crump, D., Hervé, J.C., Jones, S.P., Hahn, M.E., Karchner, S.I., Giesy, J.P., Bursian, S.J., Zwiernik, M.J., Kennedy, S.W. (2012) Sequence and in vitro function of chicken, ring-necked pheasant, and Japanese quail AHR1 predict in vivo sensitivity to dioxins. Environ Sci Technol. 46(5), 2967-75.

15. Mimura, J., and Fujii-Kuriyama, Y. (2003). Functional role of AhR in the expression of toxic effects by TCDD. Biochimica et Biophysica Acta - General Subjects 1619, 263-268.

16. Wirgin, I., Roy, N. K., Loftus, M., Chambers, R. C., Franks, D. G., and Hahn, M. E. (2011). Mechanistic basis of resistance to PCBs in Atlantic tomcod from the Hudson River. Science 331, 1322-1325

17. Kopf, P. G., and Walker, M. K. (2009). Overview of developmental heart defects by dioxins, PCBs, and pesticides. J. Environ. Sci. Health C. Environ. Carcinog. Ecotoxicol. Rev. 27(4), 276-285.

18. Lavine, J.A.; Rowatt, A.J.; Klimova, T.; Whitington, A.J.; Dengler, E.; Beck, C.; Powell, W.H. 2005. Aryl hydrocarbon receptors in the frog Xenopus laevis: two AhR1 paralogs exhibit low affinity for 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD). Toxicol. Sci. 88 (1), 60-72.

19. Shoots, J.; Fraccalvieri, D.; Franks, D.G.; Denison, M.S.; Hahn, M.E.; Bonati, L.; Powell, W.H. 2015. An aryl hydrocarbon receptor from the salamander Ambystoma mexicanum exhibits low sensitivity to 2,3,7,8-tetrachlorodibenzo-p-dioxin. Enviro. Sci. Technol. 49, 6993-7001.

20. Oka, K.; Kohno, S.; Ohta, Y.; Guillette, L.J.; Iguchi, T.; Katsu, Y. (2016). Molecular cloning and characterization of the aryl hydrocarbon receptors and aryl hydrocarbon receptor nuclear translocators in the American alligator. Gen. Comp. Endo. 238, 13-22.

21. Doering, J.A.; Giesy, J.P.; Wiseman, S.; Hecker, M. Predicting the sensitivity of fishes to dioxin-like compounds: possible role of the aryl hydrocarbon receptor (AhR) ligand binding domain. Environ. Sci. Pollut. Res. Int. 2013, 20(3), 1219-1224.

22. Doering, J.A.; Farmahin, R.; Wiseman, S.; Kennedy, S.; Giesy J.P.; Hecker, M. 2014. Functionality of aryl hydrocarbon receptors (AhR1 and AhR2) of white sturgeon (Acipenser transmontanus) and implications for the risk assessment of dioxin-like compounds. Enviro. Sci. Technol. 48, 8219-8226.

Abnet, C.C.; Tanguay, R.L.; Heideman, W.; Peterson, R.E. 1999. Transactivation activity of human, zebrafish, and rainbow trout aryl hydrocarbon receptors expressed in COS-7 cells: Greater insight into species differences in toxic potency of polychlorinated dibenzo-p-dioxin, dibenzofuran, and biphenyl congeners. Toxicol. Appl. Pharmacol. 159, 41-51.

Bisson, W.H.; Koch, D.C.; O’Donnell, E.F.; Khalil, S.M.; Kerkvliet, N.I.; Tanguay, R.L.; Abagyan, R.; Kolluri, S.K. 2009. Modeling of the aryl hydrocarbon receptor (AhR) ligand binding domain and its utility in virtual ligand screening to predict new AhR ligands. J. Med. Chem. 52, 5635-5641.

Brinkmann, M.; Koglin, S.; Eisner, B.; Wiseman, S.; Hecker, M.; Eichbaum, K.; Thalmann, B.; Buchinger, S.; Reifferscheid, G.; Hollert, H. 2016. Characterization of transcriptional responses to dioxins and dioxin-like contaminants in roach (Rutilus rutilus) using whole transcriptome analysis. Sci. Totl. Enviro. 541, 412-423.

Buckler J.; Candrl, J.S.; McKee, M.J.; Papoulias, D.M.; Tillitt, D.E.; Galat, D.L. Sensitivity of shovelnose sturgeon (Scaphirhynchus platorynchus) and pallid sturgeon (S. albus) early life stages to PCB-126 and 2,3,7,8-TCDD exposure. Enviro. Toxicol. Chem. 2015, 34(6), 1417-1424.

Clark, B.W.; Matson, C.W.; Jung, D.; Di Giulio, R.T. 2010. AHR2 mediates cardiac teratogenesis of polycyclic aromatic hydrocarbons and PCB-126 in Atlantic killifish (Fundulus heteroclitus). Aquat. Toxicol. 99, 232-240.

Doering, J.A.; Tang, S.; Peng, H.; Eisner, B.K.; Sun, J.; Giesy, J.P.; Wiseman, S.; Hecker, M. 2016. High conservation in transcriptomic and proteomic response of white sturgeon to equipotent concentrations of 2,3,7,8-TCDD, PCB 77, and benzo[a]pyrene. Enviro. Sci. Technol. 50 (9), 4826-4835.

Doering, J.A.; Giesy, J.P.; Wiseman, S.; Hecker, M. Predicting the sensitivity of fishes to dioxin-like compounds: possible role of the aryl hydrocarbon receptor (AhR) ligand binding domain. Environ. Sci. Pollut. Res. Int. 2013, 20(3), 1219-1224.

Dong, W.; Matsumura, F.; Kullman, S.W. (2010). TCDD induced pericardial edema and relative COX-2 expression in medaka (Oryzias latipes) embryos. Toxicol. Sci. 118 (1), 213-223.

Duncan, D.M.; Burgess, E.A.; Duncan, I. 1998. Control of distal antennal identity and tarsal development in Drosophila by spineless-aristapedia, a homolog of the mammalian dioxin receptor. Genes Dev. 12, 1290-1303.

Elonen, G.E.; Spehar, R.L.; Holcombe, G.W.; Johnson, R.D.; Fernandez, J.D.; Erickson, R.J.; Tietge, J.E.; Cook, P.M. Comparative toxicity of 2,3,7,8-tetrachlorodibenzo-p-dioxin to seven freshwater fish species during early life-stage development. Enviro. Toxico. Chem. 1998, 17, 472-483.

Ema, M.; Ohe, N.; Suzuki, M.; Mimura, J.; Sogawa, K.; Ikawa, S.; Fujii-Kuriyama, Y. 1993. Dioxin binding activities of polymorphic forms of mouse and human aryl hydrocarbon receptors. J. Biol. Chem. 269 (44), 27337-27343

Emmons, R.B.; Duncan, D.; Estes, P.A.; Kiefel, P.; Mosher, J.T.; Sonnenfeld, M.; Ward, M.P.; Duncan, I.; Crews, S.T. 1999. The spineless-aristapedia and tango bHLH-PAS proteins interact to control antennal and tarsal development in Drosophila. Development. 126, 3937-3945.

Farmahin, R.; Manning, G.E.; Crump, D.; Wu, D.; Mundy, L.J.; Jones, S.P.; Hahn, M.E.; Karchner, S.I.; Giesy, J.P.; Bursian, S.J.; Zwiernik, M.J.; Fredricks, T.B.; Kennedy, S.W. 2013. Amino acid sequence of the ligand-binding domain of the aryl hydrocarbon receptor 1 predicts sensitivity of wild birds to effects of dioxin-like compounds. Toxicol. Sci. 131 (1), 139-152.

Farmahin, R.; Wu, D.; Crump, D.; Herve, J.C.; Jones, S.P.; Hahn, M.E.; Karchner, S.I.; Giesy, J.P.; Bursian, S.J.; Zwiernik, M.J.; Kennedy, S.W. 2012. Sequence and in vitro function of chicken, ring-necked pheasant, and Japanese quail AHR1 predict in vivo sensitivity to dioxins. Enviro. Sci. Toxicol. 46 (5), 2967-2975.

Hahn, M.E. 2002. Aryl hydrocarbon receptors: diversity and evolution. Chemico-Biol. Interact. 141, 131-160.

Hahn, M.E.; Poland, A.; Glover, E.; Stegeman, J.J. 1994. Photoaffinity labeling of the Ah receptor: phylogenetic survey of diverse vertebrate and invertebrate species. Arch. Biochem. Biophys. 310, 218-228.

Huang, L.; Zuo, Z.; Zhang, Y.; Wu, M.; Lin, J.J.; Wang, C. 2014. Use of toxicogenomics to predict the potential toxic effects of benzo(a)pyrene on zebrafish embryos: Ocular developmental toxicity. Chemosphere. 108, 55-61.

Lahvis, G.P.; Bradfield, C.A. 1998. Ahr null alleles: distinctive or different? Biochem. Pharmacol. 56, 781-787.

Li, Z.; Xu, H.; Zheng, W.; Lam, S.H.; Gong, Z. 2013. RNA-sequencing analysis of TCDD-induced responses in zebrafish liver reveals high relatedness to in vivo mammalian models and conserved biological pathways. PLOS ONE. 8 (10), e77292.

Jung, R.E.; Walker, M.K. (1997). Effects of 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) on development of anuran amphibians. Enviro. Toxicol. Chem. 16 (2), 230-240.

Fernandez-Salquero, P.M.; Hilbert, D.M.; Rudikoff, S.; Ward, J.M.; Gonzalez, F.J. (1996). Aryl-hydrocarbon receptor-deficient mice are resistant to 2,3,7,8-tetrachlorodibenzo-p-dioxin-induced toxicity. Toxicol. Appl. Pharmacol. 140 (1), 173-179.

Karchner, S.I.; Franks, D.G.; Kennedy, S.W.; Hahn, M.E. 2006. The molecular basis for differential dioxin sensitivity in birds: Role of the aryl hydrocarbon receptor. Proc. Natl. Acad. Sci. USA. 103, 6252-6257.

Lavine, J.A.; Rowatt, A.J.; Klimova, T.; Whitington, A.J.; Dengler, E.; Beck, C.; Powell, W.H. 2005. Aryl hydrocarbon receptors in the frog Xenopus laevis: two AhR1 paralogs exhibit low affinity for 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD). Toxicol. Sci. 88 (1), 60-72.

Johnson, R.D.; Tietge, J.E.; Jensen, K.M.; Fernandez, J.D.; Linnum, A.L.; Lothenbach, D.B.; Holcombe, G.W.; Cook, P.M.; Christ, S.A.; Lattier, D.L.; Gordon, D.A. Toxicity of 2,3,7,8-tetrachlorodibenzo-p-dioxin to early life stage brooke trout (Salvelinus fontinalis) following parental dietary exposure. Enviro. Toxicol. Chem. 1998, 17 (12), 2408-2421.

Kopf, P.G.; Walker, M.K. (2009). Overview of developmental heart defects by dioxins, PCBs, and pesticides. J. Environ. Sci. Health C. Environ. Carcinog. Ecotoxicol. Rev. 27 94), 276-285.

Manning G.E.; Farmahin, R.; Crump, D.; Jones, S.P.; Klein, J.; Konstantinov, A.; Potter, D.; Kennedy, S.W. 2012. A luciferase reporter gene assay and aryl hydrocarbon receptor 1 genotype predict the LD50 of polychlorinated biphenyls in avian species. Toxicol. Appl. Pharm. 263, 390-401.

Park, Y.J.; Lee, M.J.; Kim, H.R.; Chung, K.H.; Oh, S.M. Developmental toxicity of 2,3,7,8-tetrachlorodibenzo-p-dioxin in artificially fertilized crucian carp (Carassius auratus) embryo. Sci. Totl. Enviro. 2014, 491-492, 271-278.

Prasch, A.L.; Teraoka, H.; Carney, S.A.; Dong, W.; Hiraga, T.; Stegeman, J.J.; Heideman, W.; Peterson, R.E. 2003. Toxicol. Sci. Aryl hydrocarbon receptor 2 mediated 2,3,7,8-tetrachlorodibenzo-p-dioxin developmental toxicity in zebrafish. 76 (1), 138-150.

Shoots, J.; Fraccalvieri, D.; Franks, D.G.; Denison, M.S.; Hahn, M.E.; Bonati, L.; Powell, W.H. 2015. An aryl hydrocarbon receptor from the salamander Ambystoma mexicanum exhibits low sensitivity to 2,3,7,8-tetrachlorodibenzo-p-dioxin. Enviro. Sci. Technol. 49, 6993-7001.

Teraoka, H.; Kubota, A.; Kawai, Y.; Hiraga, T. (2008). Prostanoid signaling mediates circulation failure caused by TCDD in developing zebrafish. Interdis. Studies Environ. Chem. Biol. Resp. Chem. Pollut. 61-80.

Teraoka, H.; Okuno, Y.; Nijoukubo, D.; Yamakoshi, A.; Peterson, R.E.; Stegeman, J.J.; Kitazawa, T.; Hiraga, T.; Kubota, A. (2014). Involvement of COX2-thromboxane pathway in TCDD-induced precardiac edema in developing zebrafish. Aquat. Toxicol. 154, 19-25.

Tillitt, D.E.; Buckler, J.A.; Nicks, D.K.; Candrl, J.S.; Claunch, R.A.; Gale, R.W.; Puglis, H.J.; Little, E.E.; Linbo, T.L.; Baker, M. Sensitivity of lake sturgeon (Acipenser fulvescens) early life stages to 2,3,7,8-tetrachlorodibenzo-p-dioxin and 3,3’,4,4’,5-pentachlorobiphenyl. 2015. Enviro. Toxicol. Chem. DOI: 10.1002/etc.3614.

Van den Berg, M.; Birnbaum, L.; Bosveld, A.T.C.; Brunstrom, B.; Cook, P.; Feeley, M.; Giesy, J.P.; Hanberg, A.; Hasegawa, R.; Kennedy, S.W.; Kubiak, T.; Larsen, J.C.; van Leeuwen, R.X.R.; Liem, A.K.D.; Nolt, C.; Peterson, R.E.; Poellinger, L.; Safe, S.; Schrenk, D.; Tillitt, D.; Tysklind, M.; Younes, M.; Waern, F.; Zacharewski, T. Toxic equivalency factors (TEFs) for PCBs, PCDDs, PECDFs for human and wildlife. Enviro. Hlth. Persp. 1998, 106, 775-792.

Van Tiem, L.A.; Di Giulio, R.T. 2011. AHR2 knockdown prevents PAH-mediated cardiac toxicity and XRE- and ARE-associated gene induction in zebrafish (Danio rerio). Toxicol. Appl. Pharmacol. 254 (3), 280-287.

Wang, Y.; Wang, Q.; Wu, B.; Li, Y.; Lu, G. (2013). Correlation between TCDD acute toxicity and aryl hydrocarbon receptor structure for different mammals. Ecotox. Enviro. Saf. 89, 84-88.

Whitehead, A.; Triant, D.A.; Champlin, D.; Nacci, D. 2010. Comparative transcriptomics implicates mechanisms of evolved pollution tolerance in a killifish population. Molec. Ecol. 19, 5186-5203.

Carreira VS, Fan Y, Kurita H, Wang Q, Ko C-I, Naticchioni M, et al. (2015) Disruption of Ah Receptor Signaling during Mouse Development Leads to Abnormal Cardiac Structure and Function in the Adult. PLoS ONE 10(11): e0142440. doi:10.1371/journal.pone.0142440