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

Rolling mouse名古屋（RMN）是一种编码P/Q型Ca^2+通道α亚基基因突变的共济失调突变型小鼠<1A>。在人类中，该基因的缺陷导致Ca^2+通道病，如家族性偏瘫性偏头痛和发作性共济失调2型。促肾上腺皮质激素释放因子（CRF）广泛分布于中枢神经系统。在小脑中，CRF存在于爬行纤维和苔藓纤维的亚群中，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阳性小脑传入纤维在RMN共济失调症状的发展中的作用。在RMN中，CRF在某些爬行纤维和苔藓纤维中的免疫染色更强，但这些纤维的分布与非共济失调同窝出生的小鼠（对照小鼠）中的相同。CRF和酪氨酸羟化酶（TH）双重免疫组化染色显示，CRF组部分浦肯野细胞出现TH免疫组化异常 ...更多信息 - 阳性攀爬纤维半定量原位杂交结果显示，RMN攀缘纤维的部分原始神经元中CRF mRNA的表达水平增加。RMN中β核和下橄榄体腹外侧突起（ION）的信号水平约为对照组的2倍。RMN的ION的背核、主核和A亚核的信号水平略高于对照组，但有显著性差异。在前庭小脑，CRF阳性苔藓纤维的数量在RMN比对照组明显增加。CRF和calretinin的双重免疫荧光显示，一些CRF阳性苔藓纤维与calretinin阳性单极刷细胞紧密对立，它们在放大前庭小脑苔藓纤维的兴奋性输入中起作用。这些结果表明，在特定的爬行纤维和苔藓纤维亚群中，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