Gene expression during gonadogenesis in the chicken embryo

Genes implicated in vertebrate sex determination and differentiation were s tudied in embryonic chicken gonads using reverse transcription and the poly merase chain reaction (RT-PCR). Expression profiles were obtained during go nadal sex differentiation for AMH, SOX9, SOX3, the Wilm's Tumour gene, WT1, and the orphan nuclear receptor genes, SF1 and DAX1. Some of these genes s howed sexually dimorphic expression profiles during gonadal development, wh ereas others were expressed at similar levels in both sexes. The gene encod ing Anti-Mullerian hormone (AMH) was expressed in both sexes prior to and d uring sexual differentiation of the gonads, with levels of expression consi stently higher in males than in females. SOX9 expression was male-specific, and was up-regulated after the detection of AMH transcripts. SOX3 expressi on was observed prior to clear SOX9 expression and was up-regulated in both sexes at the onset of gonadal sex differentiation (but declined later in d evelopment). The WT1 gene was highly expressed in both sexes, whereas SF1 e xpression was dearly higher in developing ovaries compared to testes. DAX1 transcripts were observed in both sexes at all stages examined, but express ion appeared somewhat higher in developing ovaries. These expression profil es are analysed in terms of current theories of vertebrate sex determinatio n. (C) 1999 Elsevier Science B.V. All rights reserved.