Studies of molecular mechanisms on the sexual determination and differentiation

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The sex of birds is determined genetically. The bird with homogametic sex (ZZ) is male and has the testis, and the bird with heterogametic sex (ZW) is female and has the ovary. However, there are many unknown mechanisms about the gene expression in related with sexual determination and differentiation. We examined the gene expression of anti-Mullerian hormone (AMH), P450 cl17hydroxylase (P450c17) and P450aromatase (P450arom) in the gonads in chick embryo by in situ hybridization. Although, AMH mRNA was not detected in female gonad. from day 5 of incubation and increased with development, AMH mRNA was not detected in female gonad. P450c17 mRNA was detected in male and female gonads from day 5 of incubation. Although, P450arom mRNA was detected in the female gonad from day 5 of incubation and increased with development, P450arom mRNA was not detected in male gonad. When the female crick was injected with aromatase inhibitor at day 3 of incubation, the level P450arom mRNA was inhibited and the level of AMH mRNA was enhanced. When the male chick was injected with estradiol at day 3 of incubation, the level of AMH mRNA was inhibited and the level of P450arom m RNA was enhanced. These results suggested that AMH and P450arom may be a rival relation for sexual differentiation, and AMH has an important role for male and P450arom has an important role for female.