Functional analysis of attractin (Atrn) using a mutant rat with attractin deficiency

髓鞘空泡化（myelin vacuolization，MV）是一种以中枢神经系统空泡化为特征的突变型大鼠，其病变是由attractin基因的无效突变引起的。本项目旨在阐明mv大鼠的发病机制，并分析吸引素蛋白在髓鞘形成和维持中的作用。我们使用2 - 24周龄的mv和对照（杂合子或野生型）。从腰脊髓制备冷冻切片，并使用针对CNP、GFAP、OX-42和OX-6的抗体进行免疫组织化学，以评估各种胶质细胞的动力学。为了研究少突胶质细胞和少突胶质细胞前体的动力学，还使用针对PLP和PDGF α受体mRNA的RNA探针进行原位杂交。mv后2周大鼠脊髓内可见髓鞘减少、变细和分裂。随着年龄的增长，髓鞘病变逐渐加重。少突胶质细胞的数量与对照组相比无统计学差异。从mv大鼠2周开始观察到大量肥大的星形胶质细胞，这些活化的星形胶质细胞分布在髓鞘病变处，提示髓鞘病变与星形胶质细胞的活化密切相关。在脊髓灰质中发现许多活化的小胶质细胞，而不是在白色物质中发现明显的髓鞘病变。PLP阳性和PDFF α受体阳性细胞数无明显差异。这些结果表明，缺乏吸引素会间接导致小胶质细胞的激活和髓鞘功能障碍。

mv (myelin vacuolation) is a mutant rat characterized by vacuolation in the central nervous system and lesion is caused by a null mutation in attractin gene. This project was aimed to clarify the pathogenesis of mv rat and to analyze the function of attractin protein for myelination and maintenance in myelin. We used 2-24 week-old mv and control (heterozygote or wild type). Frozen sections were prepared from the lumber spinal cord and immunohistochemistry was conducted using antibody against CNP, GFAP, OX-42, and OX-6 to evaluate the kinetics of various glial cells. To study the kinetics of oligodendrocyte and precursor of oligodendrocyte, in situ hybridization was also carried out using RNA probes against PLP and PDGF alpha-receptor mRNA. Hypomyelination, attenuation and splitting of myelin were found in the spinal cords from 2 weeks of mv rat. Myelin lesion gradually deteriorated with ageing. There is no statistic differences in the number of oligodendrocytes between the mv and control rats. Increasing and hypertrophic astrocytes were observed from 2 weeks of mv rat and these activated astrocytes distributed in the myelin lesion, suggesting a close correlation between the myelin lesion and activation of astrocytes. Many activated microglias were found in the gray matter of spinal cord rather than the white matter where marked myelin lesion were noted. No obvious differences in number of PLP positive and PDFF alpha-receptor positive cells. These findings suggested that absence of attractin causes an activation of microglia and dysfunction in myelin indirectly.