Numakawa Tadahiro, Yagasaki Yuki, Ishimoto Tetsuya, Okada Takeya, Suzuki Tatsuyo, Iwata Nakao, Ozaki Norio, Taguchi Takahisa, Tatsumi Masahiko, Kamijima Kunitoshi, Straub Richard E, Weinberger Daniel R, Kunugi Hiroshi, Hashimoto Ryota
Department of Mental Disorder Research, National Institute of Neuroscience, National Center of Neurology and Psychiatry, 4-1-1 Ogawahigashicho, Kodaira, Tokyo 187-8502, Japan.
Hum Mol Genet. 2004 Nov 1;13(21):2699-708. doi: 10.1093/hmg/ddh280. Epub 2004 Sep 2.
Genetic variation in dysbindin (DTNBP1: dystrobrevin-binding protein 1) has recently been shown to be associated with schizophrenia. The dysbindin gene is located at chromosome 6p22.3, one of the most promising susceptibility loci in schizophrenia linkage studies. We attempted to replicate this association in a Japanese sample of 670 patients with schizophrenia and 588 controls. We found a nominally significant association with schizophrenia for four single nucleotide polymorphisms and stronger evidence for association in a multi-marker haplotype analysis (P = 0.00028). We then explored functions of dysbindin protein in primary cortical neuronal culture. Overexpression of dysbindin induced the expression of two pre-synaptic proteins, SNAP25 and synapsin I, and increased extracellular basal glutamate levels and release of glutamate evoked by high potassium. Conversely, knockdown of endogenous dysbindin protein by small interfering RNA (siRNA) resulted in the reduction of pre-synaptic protein expression and glutamate release, suggesting that dysbindin might influence exocytotic glutamate release via upregulation of the molecules in pre-synaptic machinery. The overexpression of dysbindin increased phosphorylation of Akt protein and protected cortical neurons against neuronal death due to serum deprivation and these effects were blocked by LY294002, a phosphatidylinositol 3-kinase (PI3-kinase) inhibitor. SiRNA-mediated silencing of dysbindin protein diminished Akt phosphorylation and facilitated neuronal death induced by serum deprivation, suggesting that dysbindin promotes neuronal viability through PI3-kinase-Akt signaling. Genetic variants associated with impairments of these functions of dysbindin could play an important role in the pathogenesis of schizophrenia.
最近研究表明，联结蛋白（DTNBP1：肌萎缩蛋白结合蛋白1）的基因变异与精神分裂症有关。联结蛋白基因位于6号染色体p22.3，这是精神分裂症连锁研究中最具潜力的易感基因座之一。我们试图在一个包含670例精神分裂症患者和588例对照的日本样本中重复这一关联研究。我们发现4个单核苷酸多态性与精神分裂症存在名义上的显著关联，并且在多标记单倍型分析中有更强的关联证据（P = 0.00028）。然后，我们在原代皮质神经元培养中探究了联结蛋白的功能。联结蛋白的过表达诱导了两种突触前蛋白SNAP25和突触素I的表达，并增加了细胞外基础谷氨酸水平以及高钾诱发的谷氨酸释放。相反，通过小干扰RNA（siRNA）敲低内源性联结蛋白会导致突触前蛋白表达和谷氨酸释放减少，这表明联结蛋白可能通过上调突触前机制中的分子来影响谷氨酸的胞吐释放。联结蛋白的过表达增加了Akt蛋白的磷酸化，并保护皮质神经元免受血清剥夺所致的神经元死亡，而这些作用被磷脂酰肌醇3激酶（PI3激酶）抑制剂LY294002阻断。SiRNA介导的联结蛋白沉默会减少Akt磷酸化，并促进血清剥夺诱导的神经元死亡，这表明联结蛋白通过PI3激酶 - Akt信号通路促进神经元存活。与联结蛋白这些功能受损相关的基因变异可能在精神分裂症的发病机制中起重要作用。
