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研究発表を行った学会；
・第４３回日本発生生物学会年会.
　２０１０年　６月２０日〜２３日（京都）

タイトル；Draxin is essential for the guidance of thalamocortical projections.
　
発表者；　新明　洋平　氏
　　　（熊本大学　大学院生命科学研究部　神経分化学分野）

Abstract；
The correct selection of axonal path toward to their target is known accomplished by extracellular guidance molecules. We have identified a novel chemorepulsive protein, draxin (dorsal repulsive axon guidance protein), which is required for the midline crossing of forebrain commissures. In the present study, we addressed the function of draxin in the guidance of corticothalamic and thalamocortical projections. draxin is strongly expressed in early-born cortical neurons, including subplate and Cajal-Retzuius cells, and weakly expressed in the ventral telencephalon and dorsal thalamus. draxin deficient mice showed severe defects in the guidance of these axons at early postnatal stages: thalamocortical and corticothalamic axons followed an ectopic route through the external capsule instead of projecting to the cortex and internal capsule, respectively. We found that thalamic axons showed a pathfinding error in the internal capsule region at E14.5, when cortical axon pathfinding still appeared normal. This suggests that primary defects in the thalamic axon pathfinding cause pathfinding errors of cortical axon projections, which is consistent with the “handshake hypothesis”. The thalamocortical phenotype in draxin mutants resembles that in mutant mice of transcriptional factors, Coup-TF1, Tbr1 or FeZl, which functions in the cortex. In addition, we showed that draxin has inhibitory effects for neurite outgrowth from thalamic explants. Thus, we propose that draxin repulsion from the cortex may be essential for proper guidance of thalamocortical axons.