Sema4C expression in neural stem/progenitor cells and in adult neurogenesis induced by cerebral ischemia.

Sema4C is a transmembrane protein that belongs to axon guidance molecules of semaphorin family. Previous reports have shown that Sema4C could interact with postsynaptic protein PSD95, etc, but the expression and the role of Sema4C in neurogenesis remains unknown. In this study, whole-mount in situ hybridization result showed that Sema4C was expressed abundantly in the areas of lateral ventricle, the striatum, the wall of midbrain, and the pons/midbrain junction of E11.5 embryos brain. Neural stem/progenitor cells (NSPs) obtained from E13.5 embryonic rat midbrain are also positive for Sema4C immunoreactivity. Sema4C expression was dramatically downregulated during induction of NSP differentiation. In order to confirm the involvement of Sema4C in neurogenesis, we used the rat global cerebral ischemia model to make adult neurogenesis in vivo. The robust proliferative NSPs were monitored by labeling with bromodeoxyuridine (BrdU) within the subventricular zone and dentate gyrus that continues for at least 2 weeks. Immunohistochemistry and Western blot analysis showed that Sema4C expression was dramatically upregulated during neurogenesis after cerebral ischemia-perfusion injury. Double immunostaining and stereologic counting analysis indicated that a high proportion of BrdU-positive proliferative cells were Nestin-positive NSPs, and also, Sema4C was highly expressed in these proliferative populations at specific stages after ischemic injury. These observations provide the evidence to support a putative role of Sema4C during neurogenesis both in vivo and in vitro.