Fig 2. ahr2^osu1 mutants are resistant to TCDD-induced developmental toxicity.

(A) Lateral view of representative bright field images of 5 dpf ahr2⁺ and ahr2^osu1 zebrafish developmentally exposed to embryo medium (EM), 0.1% DMSO, or 1 ng/mL TCDD. J = jaw, E = eye, PE = pericardial edema, and YE = yolk sac edema. Black bar in bottom right corner = 100 μm. (B) A 5 dpf zebrafish embryo-larval developmental toxicity assay for ahr2⁺ and ahr2^osu1 mutants developmentally exposed to DMSO or TCDD (n = 32). The wild-type embryos exposed to TCDD exhibited significant malformations for 11 endpoints examined, including yolk sac and pericardial edema, and craniofacial malformations. No significant malformations were observed in the AHR2^-null zebrafish exposed to TCDD. Morphological evaluations were completed in a binary notation (present/absent) and statistically compared using Fisher’s exact test at p < 0.05 for each endpoint.