Involvement of Enc1 in neuronal migration and differentiation in the developing neocortex
廣田 ゆき1,鶴重 千加子1,味岡 逸樹1,2,仲嶋 一範1

The mammalian cerebral neocortex is composed of 6 layers and exerts its crucial functions in cognition. During neocortical development, neurons are generated from radial glial cells in the ventricular zone or from progenitor cells in the subventricular zone, and then radially migrate toward the pial surface of cortex. Finally neurons reach their final positions in the cortical plate, undergo terminal differentiation and maturation, and form functional circuits. In these processes, various molecular and cellular mechanisms are involved. Ectodermal-Neural Cortex-1(Enc1), also known as a nuclear matrix protein termed“nuclear restricted protein in brain(NRP/B)”, was characterized as a Kelch-related protein expressed in the developing nervous system. Kelch family proteins are involved in various cellular processes including cell migration, cytoskeletal arrangement, protein degradation and gene expression. Enc1 is expressed in the telencephalon from early developmental stages and its possible roles in neuronal differentiation and neurite development were previously suggested. However, its precise expression pattern and physiological functions during neocortical development have not been examined yet. Here, we studied the expression pattern and function of Enc1 during mouse neocortical development. Immunostaining analysis showed that Enc1 is strongly localized in the nucleus of layer Vb/VI neurons. Suppression of Enc1 disturbed radial migration and differentiation of early-born neurons. These results suggest that Enc1 controls neuronal migration and differentiation during cortical development.
Astrocyte-derived factor enhances NMDA receptor functions in human induced pluripotent stem cell-derived neurons
佐藤 薫,高橋 華奈子,重本-最上 由香里,中條 かおり,関野 祐子

The cellular reprogramming technique in which terminally differentiated somatic cells can be converted into pluripotent stem cells, named human induced pluripotent stem cells(hiPSCs), is not only a clinically-relevant but also useful in drug development because they avoid ethical issues of embryonic stem cells and allow for homogeneous derivation of human mature cell types in large quantities, potentially in an autologous fashion. Particularly, in vitro use of neurons differentiated from hiPSC(hiPSC-neurons)is expected to improve prediction accuracy in the non-clinical drug development including searching therapeutic agents and safety pharmacological assessment. To accomplish these goals, functional maturation of hiPSC-neurons is required, however, a number of challenges still remain especially in stable reproduction of neuronal circuits of hiPSC-neurons in two dimensional culture systems. Recent reports have identified some astrocyte-derived factors which are important for functional synaptic maturation. We therefore examined the effects of X, one of these astrocyte-derived factors, on the functional differentiation of hiPSC-neurons(iCell neurons, CDI)in this study. In the fura2-Ca2+ imaging experiment, although hiPSC-neurons responded to L-glutamate(L-Glu)at 1DIV, neither NMDA receptor(NMDAR)-mediated responses were detected nor were vulnerable to excitotoxicity, a key contributor to neuronal injury in several acute and chronic neurodegenerative disorders, at 7DIV. However, 5 day-treatment with X from 2DIV induced NMDAR-mediated Ca2+ influx to hiPSC-neurons through enhancing translocation of NMDAR to the cell surface. We also found that hiPSC-neurons became responsive to excitotoxicity by the treatment with X. These results suggest that X enhanced the NMDAR-mediated functions in hiPSC-neurons. Glial factors may be key molecules to achieve functional maturation and neuronal ciucuitry of hiPSC-neurons.
金子 奈穂子,澤本 和延

Phagocytosis by resting microglia promotes neuronal turnover in the adult olfactory bulb
澤田 雅人1,神谷 幸余1,稲田 浩之2,田口 和己3,岡田 淳志3,郡 健二郎3,高坂 新一4,鍋倉 淳一2,澤本 和延1,5

New neurons are continuously added and old ones eliminated thourhgout life in the adult mouse olfactory bulb(OB). Previous studies suggest that olfactory experience controls the integration of these new neurons into mature circuits. Using in vivo two-photon laser-scanning microscopy(2PLSM)and sensory manipulations in adult live mice, we have previously reported that the turnover of OB neurons is regulated in spatiotemporal and olfactory-experience-dependent manners. Here, we investigated the role of microglia in neuronal turnover in the adult OB. It has been reported that resting microglia phagocytose apoptotic newborn cells to maintain the homeostasis of hippocampal neurogenesis(Sierra et al., Cell Stem Cell, 2010). Using in vivo 2PLSM, we observed the dynamic movement of resting microglia for the formation and retraction of a phagocytic pouch in the OB. Phagocytosed neurons were observed in the pouch of microglia. Microglial phagocytic activity was enhanced and suppressed by odor enrichment and deprivation, respectively. To investigate the role of microglia in neuronal turnover in the OB, we used colony stimulating factor-1 mutant osteopetrotic(op/op)mice, in which the density of microglia is decreased in the adult OB. Most of new neurons were observed in the vicinity of microglia, suggesting that microglia support the addition of new neurons. Taken together, these results suggest that phagocytosis of dying neurons by resting microglia promotes neuronal turnover in the adult OB.
武内 恒成,松下 夏樹
愛知医科大学・医・細胞生物 生物学