Avian TVB (DR5-like) death receptor expression in hen ovarian follicles

TVB is an avian death domain-containing receptor belonging to the TNF receptor family and is proposed to be the ortholog to mammalian DR5. Although TVB receptor activation has been demonstrated to mediate apoptosis in chick embryo fibroblasts, there is essentially no information regarding TVB expression or regulation in the mature hen ovary, and in particular within the follicle granulosa layer where apoptosis is known to promote atresia. Significantly, the TVB receptor represents the fourth death domain-containing receptor (also including Fas, TNF-R1, and DR6) found to be expressed within hen granulosa cells. Levels of TVB expression are higher in prehierarchal follicles actively undergoing atresia compared to healthy follicles. However, increased TVB expression does not precede follicle death induced in vitro. Furthermore, TVB expression within granulosa cells is highest during the final stages of follicle development when follicles are not normally susceptible to undergoing atresia. These results provide evidence that TVB receptor signaling in the ovary may function in a capacity other than solely to mediate granulosa cell death and follicle atresia.