cDNA cloning and sequence analysis of a chicken gene expressed during the gonadal development and homologous to mammalian cytochrome P-450c17.

A cDNA clone, pLOA0511, was isolated from the cDNA library prepared from the left ovaries of one- to three-day-old chickens. The transcript corresponding to this cDNA clone is approx. 1.9 kb in length and is present in steroidogenic tissues (ovary, testis and adrenal gland) but is undetectable in non-steroidogenic tissues. Relative abundance of the transcript in the ovary and testis is high and developmentally regulated but is much lower in the adrenal gland. Relative levels of this transcript in the developing left ovary and the regressing right ovary of the one- to three-day-old chicken are similar. The nucleotide sequence of this cDNA clone shows significant homology to some mammalian cytochromes P-450. Out of the 508 amino acids (aa) coded, 244 and 243 aa residues are identical with those of the bovine and human cytochrome P-450c17 (steroid 17 alpha-hydroxylase/17,20 lyase), respectively. There are three highly conserved regions among the bovine, human and chicken sequences, one of which is unique to P-450c17. These data suggest strongly that this cDNA corresponds to the mRNA of a chicken cytochrome P-450c17.