Sadakata Tetsushi, Kakegawa Wataru, Shinoda Yo, Hosono Mayu, Katoh-Semba Ritsuko, Sekine Yukiko, Sato Yumi, Saruta Chihiro, Ishizaki Yasuki, Yuzaki Michisuke, Kojima Masami, Furuichi Teiichi
Advanced Scientific Research Leaders Development Unit, Gunma University, Maebashi, Gunma, Japan; JST/CREST, Kawaguchi, Saitama, Japan.
Department of Physiology, School of Medicine, Keio University, Tokyo, Japan.
PLoS One. 2014 Jun 12;9(6):e99524. doi: 10.1371/journal.pone.0099524. eCollection 2014.
Ca2+-dependent activator protein for secretion 2 (CAPS2) is a protein that is essential for enhanced release of brain-derived neurotrophic factor (BDNF) and neurotrophin-3 (NT-3) from cerebellar granule cells. We previously identified dex3, a rare alternative splice variant of CAPS2, which is overrepresented in patients with autism and is missing an exon 3 critical for axonal localization. We recently reported that a mouse model CAPS2Δex3/Δex3 expressing dex3 showed autistic-like behavioral phenotypes including impaired social interaction and cognition and increased anxiety in an unfamiliar environment. Here, we verified impairment in axonal, but not somato-dendritic, localization of dex3 protein in cerebellar granule cells and demonstrated cellular and physiological phenotypes in postnatal cerebellum of CAPS2Δex3/Δex3 mice. Interestingly, both BDNF and NT-3 were markedly reduced in axons of cerebellar granule cells, resulting in a significant decrease in their release. As a result, dex3 mice showed developmental deficits in dendritic arborization of Purkinje cells, vermian lobulation and fissurization, and granule cell precursor proliferation. Paired-pulse facilitation at parallel fiber-Purkinje cell synapses was also impaired. Together, our results indicate that CAPS2 plays an important role in subcellular locality (axonal vs. somato-dendritic) of enhanced BDNF and NT-3 release, which is indispensable for proper development of postnatal cerebellum.
分泌型钙依赖激活蛋白2（CAPS2）是一种蛋白质，对于增强小脑颗粒细胞释放脑源性神经营养因子（BDNF）和神经营养因子-3（NT-3）至关重要。我们之前鉴定出dex3，它是CAPS2一种罕见的可变剪接变体，在自闭症患者中过度表达，并且缺失对轴突定位至关重要的外显子3。我们最近报道，表达dex3的小鼠模型CAPS2Δex3/Δex3表现出自闭症样行为表型，包括社交互动和认知受损以及在陌生环境中焦虑增加。在这里，我们证实了dex3蛋白在小脑颗粒细胞轴突而非胞体-树突的定位受损，并展示了CAPS2Δex3/Δex3小鼠出生后小脑的细胞和生理表型。有趣的是，BDNF和NT-3在小脑颗粒细胞轴突中均显著减少，导致它们的释放显著降低。结果，dex3小鼠在浦肯野细胞树突分支、蚓部小叶形成和裂化以及颗粒细胞前体增殖方面出现发育缺陷。平行纤维-浦肯野细胞突触处的成对脉冲易化也受损。总之，我们的结果表明，CAPS2在增强BDNF和NT-3释放的亚细胞定位（轴突与胞体-树突）中起重要作用，这对于出生后小脑的正常发育是不可或缺的。
