Alternatively Spliced Variants of Gallus gallus TNFRSF23 Are Expressed in the Ovary and Differentially Regulated by Cell Signaling Pathways

As a result of searching recently available chicken (ch) expressed sequence tag databases, a new Tumor Necrosis Factor Receptor Super Family (TNFRSF) member with similarity to the murine (m) TNFRSF23 decoy receptor (DcR) has been identified. However, by comparison with the mTNFRSF23, there exist at least two splice variants of chTNFRSF23, one of which includes an intracellular death domain (TNFRSF23.v1) characteristic of death receptors, and the other with a truncated cytoplasmic domain of a DcR (named TNFRSF23.v2). These two splice variants of chTNFRSF23 display differential patterns of mRNA expression across various hen tissues, with the highest levels observed within reproductive tissues. More specifically, TNFRSF23.v1 is most highly expressed in preovulatory follicle granulosa cells in the ovary, whereas TNFRSF23.v2 mRNA is found at highest levels in ovarian stromal tissue. Primary culture experiments with granulosa cells determined that expression of TNFRSF23.v1 mRNA was decreased by protein kinase A signaling and enhanced by transforming growth factor (TGF) (alpha)treatment. Interestingly, TGF?1 and signaling via protein kinase C also enhanced levels of TNFRSF23.v1 expression but only in undifferentiated granulosa cells from prehierarchal follicles. Based on patterns of mRNA expression and its endocrine/paracrine regulation, we predict that ovarian chTNFRSF23 represents a modulator of granulosa cell survival and/or differentiation. Finally, the characterization of these receptor variants is of considerable interest from an evolutionary perspective in that they provide additional evidence to support a continuing divergence of TNFRSF members throughout vertebrate evolution.