Mechanism of the onset and/or development of hereditary ataxia ; Analysis by ataxic mutant mice

滚动小鼠名古屋（RMN）是一种失调性突变体，携带编码P/ q型Ca^<2+>通道α_<1A>亚基的基因突变。在人类中，该基因的缺陷导致Ca^<2+>通道病变，如家族性偏瘫性偏头痛和2型发作性共济失调。促肾上腺皮质激素释放因子（CRF）广泛分布于整个中枢神经系统。在小脑中，CRF在攀爬和苔藓纤维亚群中被发现，并在增加小脑皮质神经元对谷氨酸的敏感性中起作用。本研究旨在阐明CRF阳性的小脑传入纤维参与RMN共济失调症状的发展。在RMN中，一些攀爬和苔藓纤维的CRF免疫染色要强烈得多，但这些纤维的分布与非共济失调的窝鼠（对照小鼠）保持相同。CRF和酪氨酸羟化酶（tyrosine hydroxylase， TH）双免疫染色显示部分接受CRF的浦肯野细胞出现TH免疫染色异常。半定量原位杂交发现，RMN攀爬纤维部分原神经元中CRF mRNA表达水平升高。RMN组β核和下橄榄腹外侧突（ION）的信号水平约为对照组的2倍。在RMN中，离子背核、主核和亚核A的信号水平略高于对照组，但显著高于对照组。在前庭小脑中，RMN中crf阳性的苔藓纤维数量远多于对照组。CRF和calretinin的双重免疫荧光显示，一些CRF阳性的苔藓状纤维与calretinin阳性的单极刷状细胞密切相反，这些细胞在放大前庭小脑苔藓状纤维的兴奋输入中起作用。这些结果表明，攀爬和苔藓状纤维特定亚群中CRF水平的升高改变了小脑皮质神经元的兴奋性，参与了RMN Less的共济失调症状

Rolling mouse Nagoya (RMN) is an ataxic mutant that carries a mutation in a gene encoding for P/Q-type Ca^<2+> channel α_<1A> subunit. In humans, defects in this gene are responsible for Ca^<2+> channelopathy such as familial hemiplegic migraine and episodic ataxia type-2. Corticotropin-releasing factor (CRF) is widely localized throughout the central nervous system. In the cerebellum, CRF has been found in subsets of climbing and mossy fibers, and plays a role in increasing sensitivity of cerebellar cortical neurons to glutamate, This study aimed to clarify the involvement of CRF-positive cerebellar afferent fibers in the development of ataxic symptoms of RMNIn RMN, CRF immunostaining in some climbing and mossy fibers was much more intense, but the distribution of these fibers remained the same as in non-ataxic littermates (control mice). Double immunostaining for CRF and tyrosine hydroxylase (TH) revealed that TH immunostaining abnormally appeared in some Purkinje cells receiving CRF … More -positive climbing fibers. By semi-quantitative in situ hybridization, the level of CRF mRNA signals increased in some original neurons of the climbing fibers of RMN. Signal levels in the β-nucleus and ventrolateral protrusion of inferior olive (ION) were about two-fold higher in RMN than in the controls. Signal levels in the dorsal nucleus, principal nucleus and subnucleus A of the ION were slightly but significantly higher in RMN than in the controls. In the vestibulocerebellum, the number of CRF-positive mossy fibers was much more in RMN than in the controls. Double immunofluorecence for CRF and calretinin in revealed that some CRF-positive mossy fibers closely opposed to calretinin-positive unipolar brush cells, which play roles in amplifying excitatory inputs from vestibulocerebellar mossy fibersThese results suggest that increased level of CRF in the particular subsets of climbing and mossy fibers alters excitability of cerebellar cortical neurons, involved in the ataxic symptoms of RMN Less