シンポジウム
21 脳進化発生スケールでみる神経細胞の多様化
21 Generating cell types in cortical evolution
座長：shan Hou Pei-（National Yang-Ming Chiao-Tung University）・隈元 拓馬（東京都医学総合研究所） |
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| 2022年7月1日 16:10～16:34 沖縄コンベンションセンター 会議場B2 第5会場
2S05e-01
発生期のニワトリ大脳におけるグリア細胞発現様式
Analysis of the timing and distribution of glial cells in the developing chick pallium
*隈元 拓馬(1)、宋 祥赫(1)、丸山 千秋(1)
1. 公益財団法人 東京都医学総合研究所
*Takuma Kumamoto(1), Xianghe Song(1), Chiaki Ohtaka-Maruyama(1)
1. Tokyo Metropolitan Institute of Medical Science
Keyword: Chick pallium, glia, cortical development
The cerebral cortex of both birds and mammals is an organ that has undergone remarkable enlargement during evolution. The mammalian neocortex forms a unique six-layer structure, while the avian cortex forms a nuclear structure classified by cell type and function. Studies using classical 3H-thymidine have shown that outside-in migration is observed in the chick pallium, whereas the mammalian neocortex shows inside-out migration (Tsai, J Comp Neurol, 1981). Furthermore, in the chick dorsal pallium, neuronal production ends around E9-E10, and it is not yet known what cell types are produced after neurogenesis. Here, we focus on characterizing cell types and the lineage-dependent distribution of cells in the chick pallium after neurogenesis. First, we performed dorsal pallium-derived lineage cell labeling using conventional in ovo electroporation. We used the iOn switch, a new kind of gene switch we recently developed and can trace the cell lineage for a long time. The clearing of the whole labeled brain revealed the tangential cell migration of chick neurons along with the rostrocaudal axis. The iOn-labeled clones were then used to immunostaining for neuronal (NeuN) and astroglial (GFAP, Olig2, AQP4, PLP1, etc.) markers to determine when from which site and which type of cell originated. We also performed a spatial transcriptome analysis (Visium) of the chicken pallium to obtain high-throughput data on spatial gene expression patterns. Together with the confirmation of mRNA localization by in situ hybridization, our data have provided new insights into the timing and localization of glial cell production in chick pallium. | | 2022年7月1日 16:34～16:58 沖縄コンベンションセンター 会議場B2 第5会場
2S05e-02
Principles of cortical neurogenesis in the chick hyperpallium
*Gwenvael Le Dreau(1)
1. Sorbonne University, INSERM, CNRS, Institut de la Vision, Paris, France
Keyword: cerebral cortex, neurogenesis
The cerebral cortex, the brain region responsible for higher cognitive functions, underwent dramatic morphogenetic changes during evolution. Although the neocortex and its stereotypical six-layered architecture are unique to mammals, the sauropsids (Reptilia and Aves) also possess a cortex-like structure originating from their dorsal telencephalon. While the cortices of these evolutionarily distant amniote species present strikingly different cytoarchitectures, the basics of their development programs appear well conserved (including the progenitor subtypes, the temporal neurogenic sequence and the neuronal circuitry), hence supporting the existence of a core developmental program inherited from their stem amniote ancestor. Therefore, studying and comparing corticogenesis in mammals and sauropsids offers a new route to identify the cell types, cellular events and gene regulatory networks that control this process: those evolutionarily conserved and those that have been exploited differently or acquired de novo throughout amniote evolution. I will illustrate the relevance of this evo-devo strategy by presenting two pieces of evidence obtained in the developing hyperpallium, the cortex-like structure found in birds. First, I will show how we used the developing chick hyperpallium to discover a role for SMAD1 and SMAD5, two transcriptional factors of the canonical BMP pathway, in stimulating the self-amplification of cortical neural stem cells during early corticogenesis; and how we further established that this SMAD1/5 function is evolutionarily conserved in the mouse neocortex and is required to drive its tangential growth. Second, I will present new evidence derived from classical immunohistochemical analyses and single-cell transcriptomics, which support the idea that neurogenesis in the chick hyperpallium is spatially compartmentalized. Neurogenesis follows a mammalian-like program involving both direct and indirect neurogenesis in the lateral hyperpallium, whereas it relies essentially on direct neurogenesis in the medial hyperpallium. These findings highlight the advantages of using the chick model to dissect out the molecular mechanisms instructing direct vs. indirect neurogenesis. Combined to the technical advantages associated with its oviparous development, these features make the chick hyperpallium uniquely suited to study the early steps of cortical neurogenesis, which remain difficult to access in mammalian models. | | 2022年7月1日 16:58～17:22 沖縄コンベンションセンター 会議場B2 第5会場
2S05e-03
The role of DACH1 in human cortical development revealed by ESC-derived neural populations and cortical organoids
*Pei-Shan Hou(1), Hung-Chih Kuo(2)
1. National Yang Ming Chiao Tung University, 2. Academia Sinica
Keyword: Cortical development, hESC-derived cortical organoid, Transcriptional machinery
Higher cognitive functions rely on the comprehensive intricate circuits established by cortical projection neurons. While the cytoarchitecture and the major components of mammalian neocortex has been mapped over a century ago, how the total number and the composition of projection neurons are controlled which further facilitate the diverse biological behaviors is still obscure. Cortio-cortical projection neurons, mainly residing in upper layers, receive the information from other cortical area, incorporate, process and make the orders. The enrichment of cortic-cortical projection neurons boosts the possibilities of high-performance signals incorporation and processing based complex cortico-cortical circuits destining gaining the higher cognitive functions, especially in humans. Despite their functional importance and direct correlation with connectome complexity, the mechanism that controls the composition of cortical projection neurons among species remains unclear. Here we combined the genetic engineering and in vitro 2D and 3D cortical differentiation of hESCs to identify the molecular program driven by DACH1 secures the competence of basal radial glial cells which principally generate cortico-cortical projection neuron in the developing neocortex. | | 2022年7月1日 17:22～17:46 沖縄コンベンションセンター 会議場B2 第5会場
2S05e-04
The Long Journey to a Folding Brain: Multiple Roles of Microtubule- and Dynein-Associated Proteins in Neuronal Migration and Disorders
*Jin-Wu Tsai(1)
1. Inst Brain Sci, Natl Yang Ming Chiao Tung Univ (NYCU), Taiwan
Keyword: Cortical Development, Neuronal Migration, Dynein, Lissencephaly
Neuronal migration disorders (NMDs) are a group of brain malformations resulting from defects in neuronal migration during development of the cerebral cortex, including lissencephaly, double cortex, and periventricular nodular heterotopia. The patients often suffer from epilepsy, developmental delay, and cognitive impairments. To date, the genetic causes of a number of NMDs have been identified, such as LIS1, DCX, ARX, TUBA1A, NDE1, KATNB1, and CDK5. Many of these genes are associated with microtubules and/or the molecular motor dynein. Using in utero electroporation to knock down these genes and monitoring cellular and subcellular events with live cell imaging in brain slices, we found that LIS1 together with dynein facilitates centrosomal and nuclear movements during neuronal migration. Recently, using whole exome sequencing (WES) in a cohort of patients with cortical malformation, we further identified variants in novel genes, CEP85L and BICD2, that cause lissencephaly. We found that CEP85L is a centrosome protein localizing to the pericentriolar material, and knockdown of Cep85l causes a neuronal migration defect in mice. Similarly, BicD2 knockdown in mouse embryos inhibited neuronal migration. Surprisingly, we observed severe blockage of neuronal migration in cells overexpressing the specific lissencephaly-associated BICD2 variant p.Lys775Ter (K775X). Interestingly, BicD2 localized at the nuclear envelope (NE) through its interaction with NE protein Nesprin-2. K775X variant disrupted this interaction and further interrupted the NE recruitment of BicD2 and dynein. These findings underscore impaired centrosomal and nuclear translocation during neuronal migration as an important mechanism of lissencephaly. Investigating the highly orchestrated molecular interactions in neuronal migration helps to understand the mechanism of brain morphogenesis during development and evolution. | | 2022年7月1日 17:46～18:10 沖縄コンベンションセンター 会議場B2 第5会場
2S05e-05
ヒト固有遺伝子による大脳皮質発生と進化
Human-specific genes regulating cortical development
*鈴木 郁夫(1)
1. 東京大学大学院理学系研究科
*Ikuo K. Suzuki(1)
1. Grad Sch Sci, Univ of Tokyo, Tokyo, Japan
Keyword: evolution, human-specific, cerebral cortex
Humans are characterized by highly elaborated brain functions, empowered by enormously complex circuits composed of a tremendous number and variety of neurons. To reveal how our ancestors had acquired the specific brain features typically observed in modern humans during evolution, the comparative developmental study in humans and non-human hominids is necessary. We first comprehensively identify the genes uniquely obtained in humans by the multiple comparative omics studies. Among such human-specific genes, we then screened the ones most plausibly involved in brain development by genetic association and expression studies. Finally, the molecular function of a small number of selected human-specific genes was carefully examined. I will report the recent progress of the project, such as the human-specific molecular regulatory mechanism of neural stem cell maintenance, which leads to the production of a large number and variety of neurons, and the newly identified human-specific genes originated by various evolutionary mechanisms. | | | |
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