Makhsud Tagirov, Ukrainian Academy of Agrarian Sciences, Borky, Ukraine
Szymon Drobniak, Jagiellonian University, Krakow, Poland
Joanna Rutkowska, Jagiellonian University, Krakow, Poland
Sexual dimorphism in prenatal development is widespread among vertebrates, including birds. Its mechanism remains unclear although it is known to be connected with the effect of maternal steroid hormones. The aim of this study was to investigate how increased levels of steroid hormones in the eggs influence early embryonic development of male and female offspring. We also asked whether maternal hormones take part in the control of sex-specific expression of genes involved in prenatal development. We experimentally manipulated hormones’ concentration in the egg yolk by injecting zebra finch females prior to ovulation with testosterone or corticosterone. We assessed growth rate and expression level of CDK7, FBP1 and GHR genes in 37h-old embryos. We found faster growth and higher expression of two studied genes in male compared to female embryos. Hormonal treatment, despite clearly differentiating egg steroid levels, had no effect on the sex-specific pattern of embryonic gene expression. Our study indicates high stability of early sex differences in embryonic development before the onset of sexual differentiation and demonstrates their independence of maternal hormones in the egg.