title: The molecular genetics of ovarian differentiation in the avian model.
abstract: In birds as in mammals, sex is determined at fertilization by the inheritance of sex chromosomes. However, sexual differentiation - development of a male or female phenotype - occurs during embryonic development. Sex differentiation requires the induction of sex-specific developmental pathways in the gonads, resulting in the formation of ovaries or testes. Birds utilize a different sex chromosome system to that of mammals, where females are the heterogametic sex (carrying Z and W chromosomes), while males are homogametic (carrying 2 Z chromosomes). Therefore, while some genes essential for testis and ovarian development are conserved, important differences also exist. Namely, the key mammalian male-determining factor SRY does not exist in birds, and another transcription factor, DMRT1, plays a central role in testis development. In contrast to our understanding of testis development, ovarian differentiation is less well-characterized. Given the presence of a female-specific chromosome, studies in chicken will provide insight into the induction and function of female-specific gonadal pathways. In this review, we discuss sexual differentiation in chicken embryos, with emphasis on ovarian development. We highlight genes that may play a conserved role in this process, and discuss how interaction between ovarian pathways may be regulated.
authors.affiliation: Murdoch Childrens Research Institute, Melbourne, Vic. 3052, Australia.
authors.forename: K L
authors.initials: KL
authors.lastname: Ayers
authors.forename: A H
authors.initials: AH
authors.lastname: Sinclair
authors.forename: C A
authors.initials: CA
authors.lastname: Smith
mesh_terms: D000818:Animals; D002645:Chickens / Q000235:genetics* / Q000254:growth & development*; D005260:Female; D023421:Models, Animal; D010053:Ovary / Q000254:growth & development* / Q000378:metabolism*; D019849:Sex Determination Processes / Q000235:genetics; D012733:Sex Differentiation / Q000235:genetics*; D015398:Signal Transduction / Q000235:genetics