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幹細胞、ニューロンとグリアの分化 1
Stem Cells, Neuronal and Glial Production/Differentiation 1

開催日 2014/9/11
時間 17:00 - 18:15
会場 Room J(313+314)
Chairperson(s) 大塚 俊之 / Toshiyuki Ohtsuka (京都大学ウイルス研究所 細胞生物学研究部門 / Department of Cell Biology, Institute for Virus Research, Kyoto University, Japan)
花嶋 かりな / Carina Hanashima (理化学研究所 発生・再生科学総合研究センター / RIKEN Center for Developmental Biology, Japan)

Molecular mechanisms underlying the origin of the neocortex

  • O1-J-5-2
  • 隈元 拓馬 / Takuma Kumamoto:1 花嶋 かりな / Carina Hanashima:1 
  • 1:理化学研究所 発生・再生科学総合研究センター / RIKEN Center for Developmental Biology, Japan 

The mammalian neocortex is comprised of diverse arrays of neurons that are organized into six horizontal layers and tangential areas, and process higher-order information. The neocortical cytoarchitecture can be defined by its glutamatergic cell components: preplate neurons, deep-layer, and upper-layer projection neurons, which are sequentially generated from progenitor cells of the dorsal telencephalon during development. This unique six-layer structure is well conserved among mammals, whereas sauropsids have highly disparate brain cytoarchitecture such as a single-layered cortex in reptiles and a nuclear organization in birds. The acquisition of the laminated brain system is, therefore, one of the key events that enabled higher-order neural processing in mammals, however the molecular mechanisms underlying the mammalian-specific configuration of brain cytoarchitecture remain largely elusive.
To explore the mechanisms of neocortical establishment, we performed genome-wide transcriptome and chromatin immunoprecipitation to identify mammalian-specific cortical gene program regulated by Foxg1, a forkhead transcription factor necessary for neocortical specification. Through these approaches, we identified eight genes that are expressed in Cajal-Retzius (CR) cells, which are the earliest-born glutamatergic neurons of the cortex and expand in number during evolution. Consistent with the ChIP-seq data, comparative studies show that these candidate genes are differentially regulated in their expression amongst the mammalian and non-mammalian vertebrates. We further reveal that the sauropsid pallium exhibit changes in spatiotemporal gene expression during early development. These results imply that the cooption of mammalian-specific regulatory system and molecular diversity of CR cells may be a primary step in the acquisition of the six-layered neocortex in the mammalian vertebrates.

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