TROY, a novel member of the tumor necrosis factor receptor superfamily in the central nervous system.

Using a signal sequence trap method, we isolated TROY, a novel member of the tumor necrosis factor receptor superfamily (TNFRSF), from a mouse brain cDNA library. TROY mRNA is strongly expressed in brain and embryo. In situ hybridization analysis of the embryo showed that TROY mRNA was exclusively expressed in the epithelium of many tissues, including neuroepithelium. In the developing central nervous system, TROY mRNA was strongly expressed in the ventricular and subventricular zones, which contain neuronal and glial precursors during mouse embryogenesis that are both region-specific and stagedependent. In addition, TROY mRNA was expressed in the developing olfactory bulb from embryonic day (E) 13.5 to neonate. Next, we focused on the detailed cellular characterization of TROY-expressing cells in the developing olfactory system.TROYmRNAwas first detected in the olfactory nerve layer (ONL) of the olfactory bulb at E13.5 and was expressed most intensely in the inner ONL (ONL-i) during late embryogenesis. In the postnatal olfactory bulb, TROY-expressing cells were also detected in the glomerular layer (GL) and ONL-i. TROY was intensely expressed in olfactory ensheathing cells (OECs) of the ONL-i, which are positive for neuropeptide Y (NPY), but negative for S-100 or p75 low-affinity nerve growth factor receptor. Furthermore, TROY was also detected in glial fibrillary acidic protein (GFAP)-positive glial cells of the ONL-i and GL. Thus, TROY was expressed in some specific subsets of glial cells in the olfactory bulb, including OECs, and may play some roles in the developing and adult olfactory system.