Ji Jingmin, Hassler Melanie L, Shimobayashi Etsuko, Paka Nagendher, Streit Raphael, Kapfhammer Josef P
Anatomical Institute, Department of Biomedicine Basel, University of Basel, Pestalozzistr, 20, CH-4056 Basel, Switzerland.
Anatomical Institute, Department of Biomedicine Basel, University of Basel, Pestalozzistr, 20, CH-4056 Basel, Switzerland.
Neurobiol Dis. 2014 Oct;70:1-11. doi: 10.1016/j.nbd.2014.06.002. Epub 2014 Jun 14.
Spinocerebellar ataxias (SCAs) are hereditary diseases leading to Purkinje cell degeneration and cerebellar dysfunction. Most forms of SCA are caused by expansion of CAG repeats similar to other polyglutamine disorders such as Huntington's disease. In contrast, in the autosomal dominant SCA-14 the disease is caused by mutations in the protein kinase C gamma (PKCγ) gene which is a well characterized signaling molecule in cerebellar Purkinje cells. The study of SCA-14, therefore, offers the unique opportunity to reveal the molecular and pathological mechanism eventually leading to Purkinje cell dysfunction and degeneration. We have created a mouse model of SCA-14 in which PKCγ protein with a mutation found in SCA-14 is specifically expressed in cerebellar Purkinje cells. We find that in mice expressing the mutated PKCγ protein the morphology of Purkinje cells in cerebellar slice cultures is drastically altered and mimics closely the morphology seen after pharmacological PKC activation. Similar morphological abnormalities were seen in localized areas of the cerebellum of juvenile transgenic mice in vivo. In adult transgenic mice there is evidence for some localized loss of Purkinje cells but there is no overall cerebellar atrophy. Transgenic mice show a mild cerebellar ataxia revealed by testing on the rotarod and on the walking beam. Our findings provide evidence for both an increased PKCγ activity in Purkinje cells in vivo and for pathological changes typical for cerebellar disease thus linking the increased and dysregulated activity of PKCγ tightly to the development of cerebellar disease in SCA-14 and possibly also in other forms of SCA.
脊髓小脑共济失调（SCAs）是导致浦肯野细胞变性和小脑功能障碍的遗传性疾病。大多数SCA形式是由CAG重复序列扩增引起的，这与其他多聚谷氨酰胺疾病如亨廷顿舞蹈病类似。相比之下，在常染色体显性遗传的SCA - 14中，疾病是由蛋白激酶Cγ（PKCγ）基因突变引起的，PKCγ是小脑浦肯野细胞中一个特征明确的信号分子。因此，对SCA - 14的研究提供了一个独特的机会，以揭示最终导致浦肯野细胞功能障碍和变性的分子和病理机制。我们创建了一个SCA - 14小鼠模型，其中在SCA - 14中发现的具有突变的PKCγ蛋白在小脑浦肯野细胞中特异性表达。我们发现，在表达突变型PKCγ蛋白的小鼠中，小脑切片培养物中浦肯野细胞的形态发生了剧烈改变，与药理学激活PKC后所见的形态非常相似。在幼年转基因小鼠小脑的局部区域也观察到了类似的形态异常。在成年转基因小鼠中，有证据表明浦肯野细胞存在一些局部性丢失，但没有整体小脑萎缩。转基因小鼠在转棒试验和步行梁试验中表现出轻度小脑共济失调。我们的研究结果为体内浦肯野细胞中PKCγ活性增加以及小脑疾病典型的病理变化提供了证据，从而将PKCγ活性增加和失调与SCA - 14以及可能其他形式的SCA中小脑疾病的发展紧密联系起来。
