Mutant Ataxin-3 with an Abnormally Expanded Polyglutamine Chain Disrupts Dendritic Development and Metabotropic Glutamate Receptor Signaling in Mouse Cerebellar Purkinje Cells
Mutant Ataxin-3 with an Abnormally Expanded Polyglutamine Chain Disrupts Dendritic Development and Metabotropic Glutamate Receptor Signaling in Mouse Cerebellar Purkinje Cells
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DOI：
10.1007/s12311-013-0516-5
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发表时间：
2014-02-01
期刊：
影响因子：
3.5
通讯作者：
Hirai, Hirokazu
中科院分区：
文献类型：
--
作者：
Konno, Ayumu;Shuvaev, Anton N.;Hirai, Hirokazu
脊髓小脑性共济失调3型（SCA 3）是由共济失调蛋白3基因内CAG重复序列的异常扩增引起的。以前，我们产生的转基因小鼠（SCA 3小鼠），表达一种截短形式的共济失调蛋白-3含有异常扩大CAG重复特异性小脑浦肯野细胞（PC）。在这里，我们进一步表征这些SCA 3小鼠。晚期SCA 3小鼠PC的全细胞膜片钳分析显示，由于树突状树枝化差和完全不存在代谢型谷氨酸受体亚型1（mGluR 1）介导的突触传递逆行抑制在平行纤维末端的膜电容显著降低，AMPA受体介导的快速突触传递的整体保存。由于这些小脑表型让人想起视黄酸受体相关孤儿受体a（ROR α）缺陷的蹒跚小鼠，我们通过免疫组织化学检查了SCA 3小鼠小脑中ROR α的水平，发现SCA 3小鼠细胞核中ROR α的显着减少PC。为了证实SCA 3小鼠的缺陷是由出生后PC中突变型共济失调蛋白-3的沉积引起的，而不是由转基因插入引起的基因组破坏引起的，我们试图通过病毒载体介导的CRAG（一种促进应激蛋白降解的分子）表达来减少突变型共济失调蛋白-3在发育中的PC中的积累。伴随着突变型共济失调蛋白-3的去除，表达CRAG的PC与未转导的PC相比具有更大数量的分化树突，并且在mGluR 1激活后表现出突触传递的逆行抑制。这些结果表明，出生后的核积累的突变型共济失调蛋白-3破坏树突状细胞分化和mGluR-信号在SCA 3小鼠PC，这种破坏可能是由一个缺陷ROR α驱动的转录途径。
Spinocerebellar ataxia type 3 (SCA3) is caused by the abnormal expansion of CAG repeats within the ataxin-3 gene. Previously, we generated transgenic mice (SCA3 mice) that express a truncated form of ataxin-3 containing abnormally expanded CAG repeats specifically in cerebellar Purkinje cells (PCs). Here, we further characterize these SCA3 mice. Whole-cell patch-clamp analysis of PCs from advanced-stage SCA3 mice revealed a significant decrease in membrane capacitance due to poor dendritic arborization and the complete absence of metabotropic glutamate receptor subtype1 (mGluR1)-mediated retrograde suppression of synaptic transmission at parallel fiber terminals, with an overall preservation of AMPA receptor-mediated fast synaptic transmission. Because these cerebellar phenotypes are reminiscent of retinoic acid receptor-related orphan receptor a (ROR alpha)-defective staggerer mice, we examined the levels of ROR alpha in the SCA3 mouse cerebellum by immunohistochemistry and found a marked reduction of ROR alpha in the nuclei of SCA3 mouse PCs. To confirm that the defects in SCA3 mice were caused by postnatal deposition of mutant ataxin-3 in PCs, not by genome disruption via transgene insertion, we tried to reduce the accumulation of mutant ataxin-3 in developing PCs by viral vector-mediated expression of CRAG, a molecule that facilitates the degradation of stress proteins. Concomitant with the removal of mutant ataxin-3, CRAG-expressing PCs had greater numbers of differentiated dendrites compared to non-transduced PCs and exhibited retrograde suppression of synaptic transmission following mGluR1 activation. These results suggest that postnatal nuclear accumulation of mutant ataxin-3 disrupts dendritic differentiation and mGluR-signaling in SCA3 mouse PCs, and this disruption may be caused by a defect in a ROR alpha-driven transcription pathway.