Molecular characterization, expression and cellular localization of CYP17 gene during geese (Anser cygnoides) follicular development

As a key member of the cytochrome P450 gene superfamily, CYP17 gene encodes 17α-hydroxylase/C17,20-lyase that is critical for directing androgen synthesis. The CYP17 gene has been identified in several species, yet little is known about its distribution and expression profile during goose follicular development. In the present study, we obtained the full-length coding sequence of goose CYP17 (gCYP17) gene for the first time using RACE method. Its sequence alignment and phylogenetic analysis suggested that gCYP17 was highly conserved with those of other birds and consisted of four main functional domains like other species. Results from immunohistochemistry, quantitative real-time PCR and Western blotting suggested that gCYP17 was predominantly located in theca interna throughout follicular development. Furthermore, levels of gCYP17 reached the maximum in theca layer of the 6-8 mm follicles which were significantly higher than in those of other follicles (P < 0.05). In addition, gCYP17 was expressed at much higher levels in the F4 theca layer than the F1 follicle (P < 0.05). Therefore, these results indicated that the fluctuating expression pattern and specific cellular localization of gCYP17 during follicular development might be closely related to androgen secretion, and thereby follicular maturation.