Molecular genetical approach for multifactorial neuropsychiatric diseases

舞蹈病棘红细胞增多症（ChAc）是一种常染色体隐性遗传的人类神经退行性疾病，在脑病理学上有报道其纹状体的选择性变性。临床上，ChAc表现出亨廷顿病样神经精神症状和红细胞棘红细胞增多症，即使在兄弟病例中也观察到症状的许多变化。最近，我们发现了一个基因，CHAC（VPS 13 A）编码的蛋白命名为chorein，其中一个缺失突变被发现在日本的ChAc家族。然后，我们鉴定了小鼠CHAC基因的cDNA序列和外显子-内含子结构，并通过基因打靶技术将其引入到与人类疾病突变相对应的#60-61外显子缺失的ChAC模型小鼠中。小鼠进入老年后开始出现棘红细胞增多和运动障碍。在行为学观察中，模型小鼠的自发活动显著减少，在社会交往试验中的接触时间显著减少。脑组织病理学观察发现，突变小鼠纹状体内可见大量凋亡细胞。在神经化学测定中，多巴胺代谢产物HVA在突变小鼠中脑等部位的含量显著降低。这些发现与其他地方报道的人类结果非常一致，表明ChAc模型小鼠表现出轻度表型，成年后发病。因此，ChAc模型小鼠为研究人类疾病提供了良好的模型系统。这些小鼠是129和C57 BI/B6的杂交种，并且在sriatum和其他表型的退化程度上存在很大差异，这可能暗示修饰基因的存在。建立了本底品系、C57 BL/6 J、BALB/cbyJ和DBA/2 J三种品系的ChAc小鼠模型。只有DBA/2 J ChAc模型小鼠从出生后3个月开始体重下降。

Chorea-acanthocytosis (ChAc) is a human hereditary neurodegenerative disorder with autosomal recessive transmission, in which selective degeneration of striatum has been reported in brain pathology. Clinically, ChAc shows Huntington's disease-like neuropsychiatric symptoms and red blood cell acanthocytosis, and much variation in symptoms are observed even in brother cases. Recently, we identified the gene, CHAC (VPS13A) encoding a protein named chorein in which a deletion mutation was found in Japanese ChAc families. Then we identified the mouse CHAC cDNA sequence and the exon-intron structures of the gene, and produced a ChAc-model mouse introducing #60-61 exons-deletion corresponding to a human disease mutation by gene-targeting technique. The mice began to show acanthocytosis and motor disturbance after becoming old age. In behavioral observations, locomotor activity was significantly decreased, and the contact time at social interaction test was decreased significantly in the model mice. In the brain pathology, many apoptotic cells were observed in the striatum of the mutant mice. In neurochemical determination, dopamine-metabolite, HVA concentration decreased significantly in the portion including midbrain of the mutant mice. These findings are well consistent with the human results reported elsewhere and indicate that the ChAc-model mice showed mild phenotype with late adult onset. The ChAc-model mouse therefore provides a good model system to study the human disease. The mice are produced as hybrid of 129 and C57BI/B6, and there are much variations in the degree of degeneration in the sriatum and other phenotypes, which might suggest the existence of modifier genes. Then we produced the ChAc-model mouse with three kinds of strains-background, C57BL/6J, BALB/cbyJ, and DBA/2J. Only DBA/2J ChAc-model mice showed reduced body weight from 3 months after birth.