Sawamoto Lab 澤本研究室

The Journal of Neuroscience, November 21, 2007, 27(47):12829-12838

Cyclin-Dependent Kinase 5 Is Required for Control of Neuroblast Migration in the Postnatal Subventricular Zone

Yuki Hirota, Toshio Ohshima, Naoko Kaneko, Makiko Ikeda, Takuji Iwasato, Ashok B. Kulkarni, Katsuhiko Mikoshiba, Hideyuki Okano, and Kazunobu Sawamoto

At the lateral wall of the lateral ventricles in the adult rodent brain, neuroblasts form an extensive network of elongated cell aggregates called chains in the subventricular zone and migrate toward the olfactory bulb. The molecular mechanisms regulating this migration of neuroblasts are essentially unknown. Here, we report a novel role for cyclin-dependent kinase 5 (Cdk5), a neuronal protein kinase, in this process. Using in vitro and in vivo conditional knock-out experiments, we found that Cdk5 deletion impaired the chain formation, speed, directionality, and leading process extension of the neuroblasts in a cell-autonomous manner. These findings suggest that Cdk5 plays an important role in neuroblast migration in the postnatal subventricular zone.

Key words: Cdk5; neuroblast; migration; subventricular zone; rostral migratory stream; postnatal neurogenesis

Stem Cells. 2007 Aug 2; PMID: 17673525

β-catenin signaling promotes proliferation of progenitor cells in the adult mouse subventricular zone

Kazuhide Adachi, Zaman Mirzadeh, Masanori Sakaguchi, Toru Yamashita, Tania Nikolcheva, Yukiko Gotoh, Gary Peltz, Leyi Gong, Takeshi Kawase, Arturo Alvarez-Buylla, Hideyuki Okano, Kazunobu Sawamoto

Abstract

The subventricular zone (SVZ) is the largest germinal zone in the mature rodent brain, and it continuously produces young neurons that migrate to the olfactory bulb. Neural stem cells in this region generate migratory neuroblasts via highly proliferative transit-amplifying cells. The Wnt/β-catenin signaling pathway partially regulates the proliferation and neuronal differentiation of neural progenitor cells in the embryonic brain. Here, we studied the role of beta-catenin signaling in the adult mouse SVZ. β-catenin-dependent expression of a destabilized form of green fluorescent protein was detected in progenitor cells in the adult SVZ of Axin2-d2EGFP reporter mice. Retrovirus-mediated expression of a stabilized β-catenin promoted the proliferation of Mash1+ cells and inhibited their differentiation into neuroblasts. Conversely, the expression of Dkk1, an inhibitor of Wnt signaling, reduced the proliferation of Mash1+ cells. In addition, an inhibitor of GSK3 promoted the proliferation of Mash1+ cells, and increased the number of new neurons in the olfactory bulb 14 days later. These results suggest that β-catenin signaling plays a role in the proliferation of progenitor cells in the SVZ of the adult mouse brain.

Key Words. β-catenin, neurogenesis, cell proliferation, subventricular zone, olfactory bulb, Mash1