MYOSIN V FUNCTION IN THE NERVOUS SYSTEM

稀释致死小鼠（即，肌球蛋白V无效突变体）表现出共济失调， 抽搐伴阵挛性肢体运动，角弓反张，表明 他们的中枢神经系统功能有缺陷。死亡发生在 大约3周大。 因此，它们可以代表一个良好的模型系统， 研究与早发性相关的神经退行性疾病， 进行性癫痫稀释的小鼠模型特别吸引人 由于肌球蛋白V无效突变体表现出的独特表型， 再加上它是少数几个基因突变之一， 已鉴定出该蛋白的功能， 研究了此外，某些罕见的人类遗传疾病已被 鉴定出与稀释小鼠具有相似特征的 突变然而，由于肌球蛋白V在神经元和 非神经元组织是导致神经系统异常的主要缺陷 症状可能或可能不存在于神经组织中。第一个目标是 确定导致神经异常的细胞部位 在稀释致死的小鼠中。这将通过使用 生物化学、分子生物学和形态学的结合 包括免疫印迹、北方印迹、细胞培养和 稀释致死和野生型小鼠组织的电子显微镜检查。 有证据表明肌球蛋白V可能参与细胞器的运输 沿着肌动蛋白丝。这表明，神经缺陷， 稀释致死小鼠可能是由于受损的细胞器运输， 神经元下一个目标将是确定细胞器是否与 最终的目标是确定是否需要肌球蛋白V 用于肌动蛋白丝上的细胞器运动。这些目标将是 通过使用相关光学/电子显微镜完成， 亚细胞分级分离和体外运动性测定。 这些实验将允许比较异常的神经系统 小鼠的症状，以及特定的 这些研究很可能有助于更多的研究。 对神经细胞功能的完整理解，以及 导致小鼠和人类神经系统异常的畸变。

Dilute-lethal mice (i.e., myosin V null mutants) exhibit ataxia, convulsions with clonic limb movements, and opisthotonus suggesting that they have defects in central-nervous system function. Death occurs at about 3 weeks of age. Thus, they may represent a good model system for studying neurodegenerative disease associated with early onset, progressive epilepsies. The dilute mouse model is particularly attractive because of the distinct phenotype exhibited by the myosin V null mutants, combined with the fact that it is one of few mutations in which the gene product has been identified and the function of the protein extensively studied. Furthermore, certain rare human genetic diseases have been identified which have similar characteristics to the dilute mouse mutation. However, because myosin V is expressed in both neuronal and nonneuronal tissues the primary defect causing abnormal neurologic symptoms may or may not reside in nervous tissue. Thus, the first goal is to determine the cellular site(s) that cause the neurologic abnormalities in dilute-lethal mice. This will be accomplished through the use of a combination of biochemical, molecular biological, and morphological approaches that include immunoblots, Northern blots, cell culture and electron microscopy of dilute-lethal and wild-type mouse tissues. There is evidence that myosin V may participate in organelle transport along actin filaments. This suggests that the neurological defects in dilute-lethal mice may result from impaired organelle trafficking in neurons. The next goal will be to establish whether organelles associate with myosin V. The final goal will be to determine if myosin V is required for organelle movement on actin filaments. These goals will be accomplished through the use of correlative light/electron microscopy, subcellular fractionation, and an in vitro motility assay. These experiments will allow comparison between abnormal neurologic symptoms in mice, and altered molecular/cellular function of a specific protein myosin V. These studies are likely to contribute to a more complete understanding of nerve cell function, and the specific aberrations that cause neurologic abnormalities in mice and humans.