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研究発表を行った学会；
・第４０回日本発生生物学会・第５９回日本細胞生物学会　合同大会、2007年 5月28~30日(福岡)

タイトル；Essential role of Draxin, a novel axon guidance molecule, in mouse brain development
発表者；　新明　洋平　氏
　　　（熊本大学　大学院医学薬学研究部　神経分化学分野）
Abstract；
The correct wiring of the nervous system relies on the ability of axons and dendrites to locate and recognize their appropriate synaptic partners. The correct selection of axonal path toward to their target is known accomplished by extracellular guidance molecules such as the netrins, Slits, semaphorins and ephrins. We have identified a novel secreted protein, Draxin (Dorsal repulsive axon guidance protein), which acts as a roof plate-derived chemorepellent for commissural axons in chick spinal cord. However, Draxin roles in brain development remain unknown. To define expression patterns and functions of Draxin during mammalian brain development, we generated Draxin knockout mice by inserting a lacZ gene into exon 2 of the Draxin gene. First, we performed lacZ staining of brains of the heterozygote mice to investigate expression patterns of the Draxin gene. The lacZ expression was observed in various regions including the cerebral cortex, hippocampus, superior colliculus, cerebellum and pons during embryonic and postnatal development, but not in adult, suggesting the involvement of Draxin in development of various regions of the mouse brain. Next, we performed histological analyses of brains of the knockout mice by hematoxylin-eosin and Kluver-Barrera’s staining. We found that the knockout mice display malformations of all three commissures, the corpus callosum, hippocampal commissure and anterior commissure, in the cerebrum, while these three cerebral commissures are normally formed in the wild-type and heterozygote littermates. These results suggest a role of Draxin in midline commissural axon guidance of the mouse cerebrum. In addition, the size of the hippocampus was decreased in the knockout mice, compared with the wild-type and heterozygote littermates. These data suggest multiple requirements of Draxin for the brain formation. I will discuss possible roles of Draxin during mouse brain development.