Mechanism of Sex Differentiation in Chicken:Screening for Female and Male Specific Genes in Chicken Early Embryo

点击翻译按钮获取中文摘要

We are looking for the gene which has essential roles in determination of sexes and developmental control of reproductive organs in chick early embryo. In avian species, sex steroid hormones, especially estrogen in early embryo was reported to act a crucial function to determine the sex and in gonadal development. To obtain a clue to mechanism which regulate the steroidogenic genes, we have cloned some cDNAs and a 5'-upstream sequence of a gene which code enzymes catalyzing successive reactions in sex-steroid hormone's biosynthesis.We have previously cloned a chicken cytochrome P-450c17 cDNA. This enzyme has two kinds of activities, 17-alpha hydroxylase activity and 17,20-lyase activity. I recently discovered that an amino acid at c-terminal region of chicken P-450c17 had important role especially in its 17,20-lyase activity. And I observed an incidental conversion of an amino acid in this region led to limited loss of only 17,20-lyase activity of this enzyme. Now,I am carrying out experiments to confirm whether this 'mutated' enzyme actually exists in vivo and has a role in steroid metabolism in chicken, or not.Other works relating to sex-steroid hormone's biosynthesis are as follows: The cDNA of chicken 3-beta HSD had been cloned and its activity was confirmed by introduction of cDNA- expression vector into cos7 cells. cDNA cloning of chicken 17-beta HSD is now on the way.Complete length cDNA of chicken FSH-receptor was cloned, and specific activity binding to human FSH hormone was ascertained by expression of this cDNA in human 293 cells.A project to elucidate the cis-elements which regulate the expression of cytochrome P- 450arom gene has been recently progressed to localize at least two or more cis regulatory regions, one of which facilitates the expression of P-450arom gene in primarily cultured theca cells prepared from chicken ovarian follicles, and the other represent repressive control for the same gene's expression in chicken embryonic fibroblast cells.