Draxin-mediated Regulation of Granule Cell Progenitor Differentiation in the Postnatal Hippocampal Dentate Gyrus

The hippocampus is characterized by the presence of life-long neurogenesis. To elucidate the molecular mechanism regulating hippocampal neurogenesis, we studied the functions of the chemorepellent Draxin in neuronal proliferation and differentiation in the postnatal dentate gyrus. The present in vivo cell labeling and fate tracking analyses revealed enhanced differentiation of hippocampal neural stem and progenitor cells (hNSPCs) in the subgranular zone (SGZ) of Draxin-deficient mice. We observed a reduction in the number of BrdU-pulse labeled or Ki-67 immunopositive SGZ cells in the mutant mice. However, Draxin deficiency did not affect cell cycle duration of SGZ cells. In situ hybridization analysis indicated that the receptor component of the canonical Wnt pathway, Lrp6, is expressed in SGZ cells, including Nestin and Sox2 double-positive hNSPCs. Taken together with the previous finding that Draxin interacts physically with Lrp6, we postulate that Draxin plays a pivotal role in the regulation of Wnt-driven hNSPC differentiation to modulate the rate of neuronal differentiation in the progenitor population.