若手道場

若手道場4

2021/9/30　14:00～15:00　ZOOM 若手道場 WD4-1 髄鞘形成前オリゴデンドロサイトを可視化する Visualization of Newly Formed Oligodendrocytes ^○横山貴一, Kenji F Tanaka 慶應義塾大学　医学部　精神・神経科学教室 ^○Kiichi Yokoyama, Kenji F Tanaka Departemnt of Neuropsychiatry, Keio University School of Medicine Oligodendrocyte-lineage cells have been categorized into three developmental groups, oligodendrocyte precursor cells, pre-myelinating oligodendrocytes, and mature oligodendrocytes. A new definition based on single-cell RNA sequencing of oligodendrocyte-lineage cells subdivided the groups into 13 distinct classes. Among classes, we focused on a population “Newly Formed Oligodendrocytes (NFOL)” which expresses a gene, Long non-coding oligodendrocyte 1 (LncOL1). To examine the location, the number, and the morphology of NFOL in vivo, we generated tetracycline transactivator (tTA) knock-in mice where tTA-polyA cassette was inserted into an immediate downstream of the transcription start site of the LncOL1 gene. We crossed the line with tetO-YFP line to visualize LncOL1-tTA-captured cells. In this tTA-tetO double transgenic mouse, we found YFP expressing cells in the brain, indicating that tTA was functionally expressed under the control of the LncRNA promoter. In this LncOL1-tTA::tetO-YFP line, we observed a variety of young oligodendrocyte-lineage cells, ranging from those with radial multiple processes, which were akin to pre-myelinating oligodendrocytes, to those with parallel processes, which resemble myelin-forming oligodendrocytes. We were able to detect YFP-positive cells in the entire brain, but the cells were enriched in caudoventral areas, such as the thalamus, the midbrain, and the hindbrain. The result of this observation might reflect the timescale of tTA-mediated gene induction and the spatial regulation of endogenous LncOL1 expression.		2021/9/30　14:00～15:00　ZOOM 若手道場 WD4-2 ミエリンタンパク質L-MPZは末梢神経系の構造維持と機能に必要である Myelin protein L-MPZ is necessary for the structural maintenance and function of the peripheral nervous system ^○瀬戸口潔¹, Yoshinori Otani², Akiko Hayashi¹, Jingjing Cui³, Hiroyuki Hirai¹, Chisa Amemiya¹, Yoshihide Yamaguchi¹, Setsu Sawai⁴, Hiroko Baba^1,5 1.東京薬科大学, 2.Department of Anatomy and Neuroscience, Shimane University, 3.Institute of Acupuncture and Moxibustion, China Academy of Chinese Medical Sciences, 4.Department of Functional Anatomy, Chiba University, 5.Department of Occupational Therapy, Niigata University of Health and Welfare ^○Yuki Setoguchi¹, Yoshinori Otani², Akiko Hayashi¹, Jingjing Cui³, Hiroyuki Hirai¹, Chisa Amemiya¹, Yoshihide Yamaguchi¹, Setsu Sawai⁴, Hiroko Baba^1,5 1.Department of Molecular Neurobiology, Tokyo University of Pharmacy and Life Sciences, 2.Department of Anatomy and Neuroscience, Shimane University, 3.Institute of Acupuncture and Moxibustion, China Academy of Chinese Medical Sciences, 4.Department of Functional Anatomy, Chiba University, 5.Department of Occupational Therapy, Niigata University of Health and Welfare Large-myelin protein zero (L-MPZ), an isoform of myelin protein zero (MPZ, P0), is produced by translational readthrough in the physiological state. L-MPZ mice, which synthesize only L-MPZ but not P0 by genome-editing technique, present Charcot-Marie-Tooth disease-like phenotype, such as motor disturbance and abnormal morphologies in myelin and axon. However, the physiological role of L-MPZ in the peripheral nervous system remains unknown. To investigate the functional significances of L-MPZ in vivo, we generated another genome-edited mouse line, L-MPZ KO mice those produce only P0 but not L-MPZ. In this study, to examine the motor nerve function of L-MPZ KO mice, behavioral tests and electrophysiological study were performed in 6- and 12-month-old L-MPZ KO mice. Although rotarod test, tail suspension test, and motor nerve conduction velocity showed no differences compared to wild type control mice, the amplitude of the compound muscle action potential was significantly decreased in L-MPZ KO mice. To know the influence of L-MPZ deficiency in pathological condition, demyelination was induced by lysolecithin injection in the sciatic nerves of 8- to 10-week-old L-MPZ KO mice. The demyelination areas in the lysolecithin-injected nerves of L-MPZ KO mice were larger than those of wild-type mice at 7 days after injection. These results suggest that loss of L-MPZ may induce the formation of fragile myelin and exacerbate demyelination. Thus, L-MPZ is necessary for the structural maintenance and function of the peripheral nervous system myelin.

2021/9/30　14:00～15:00　ZOOM 若手道場 WD4-3 シュワン細胞の発達におけるRNAヘリカーゼDdx20の機能解析 Analysis of the effect of RNA helicase Ddx20 on Schwann cell development in peripheral nervous system ^○益子洋樹, Norihisa Bizen, Hirohide Takebayashi 新潟大学大学院医歯学総合研究科脳機能形態学分野 ^○Hiroki Mashiko, Norihisa Bizen, Hirohide Takebayashi Division of Neurobiology and Anatomy,Graduate School of Medical and Dental Sciences, Niigata University Schwann cells form the myelin sheaths around axons and regulate the axonal conduction in the peripheral nervous system. The failure of Schwann cell development leads to the misregulation of neuronal networks and thereby serious intractable neuronal disorders such as Charcot-Marie-Tooth disease. We have demonstrated that an RNA helicase Ddx20 (DEAD box protein 20), which has been known to play a role in the assembly of small nuclear ribonucleoprotein (snRNP) and transcriptional regulation, is indispensable for the oligodendrocytes differentiation and myelination in the central nervous system (Simankova and Bizen et al.in revision). To elucidate the role of Ddx20 in Schwann cell development, we generated the mice with Schwann cell-specific depletion of Ddx20 (P0-Cre; Ddx20 cKO). These mice died immediately after birth. Immunohistochemistry and in situ hybridization demonstrated that Ddx20 ablation induced p53 accumulation and p53 target gene expressions in Schwann cells at late embryonic stages. These results implicate that p53 activation has a deleterious impact on Schwann cell development.