Expression of Transforming Growth Factor-β mRNA in Chicken Ovarian Follicular Tissue

RNA was isolated from chicken thecal tissue from the largest (F1), third largest (F3), and fifth largest (F5) preovulatory follicles, from small yolky follicles, and from granulosa tissue from F1 follicles. Transforming growth factor β (TGF-β) gene expression was measured using reverse transcription polymerase chain reaction. Thecal cells from all follicles sizes expressed all three isoforms of TGF-β. TGF-β 1 mRNA was detected in granulosa cells at levels comparable to those seen in thecal cells. However, TGF-β 2 and TGF-β 3 mRNA was expressed at significantly lower levels in granulosa than in thecal tissue. This is the first demonstration of TGF-β gene expression in the ovary of a nonmammalian species. The similarities between mammalian and avian TGF-β gene expression are remarkable, especially in light of the distinctive patterns of avian follicular development and the differing steroidogenic capacities of ovarian cell types of the two classes of vertebrates.