The role of Pax6 gene in vertebrate neural development

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During development of the brain, numerous neurons of various different types are generated and delivered at their right positions, and the axons project their own targets to make correct neuronal networks. Recent advance in developmental neurobiology has revealed that such neuronal localization and axonal projection are based on the brain patterning. Pax6 is a member of the vertebrate Pax gene family, which encode transcriptional factors. Pax6 is expressed in discrete domains in the developing forebrain, hindbrain, and spinal cord. This research project aimed to elucidate roles of Pax6 in patterning the brain at cellular and molecular levels. We obtained the following results during the period supported by this grant.1) We performed tracing of neuroepithelial cells labeled with Dil under mouse whole embryo culture, and elucidated when and how the boundary between the cortex and striatum is formed at the cellular level.2) In situ hybridization revealed exclusive expression patterns of the two members of cadherin cell adhesion molecules, Rcadherin and cadherin6, in the cortex and striatum, respectively.3) Electroporation of exogenous genes into the cultured mouse embryos demonstrated that exclusive expression patterns these cadherins play important roles in maintaining the cortex/striatum boundary.4) Tracing neuroepithelial cells in the cadherin6 knockout mice revealed that the boundary between the cortex and striatum was formed but that movement of the striatal neuroepithelial cells increased.