Ishizuka K, Fujita Y, Kawabata T, Kimura H, Iwayama Y, Inada T, Okahisa Y, Egawa J, Usami M, Kushima I, Uno Y, Okada T, Ikeda M, Aleksic B, Mori D, Someya To, Yoshikawa T, Iwata N, Nakamura H, Yamashita T, Ozaki N
Department of Psychiatry, Nagoya University Graduate School of Medicine, Nagoya, Japan.
Department of Molecular Neuroscience, Osaka University Graduate School of Medicine, Osaka, Japan.
Transl Psychiatry. 2017 Aug 1;7(8):e1184. doi: 10.1038/tp.2017.173.
CX3CR1, a G protein-coupled receptor solely expressed by microglia in the brain, has been repeatedly reported to be associated with neurodevelopmental disorders including schizophrenia (SCZ) and autism spectrum disorders (ASD) in transcriptomic and animal studies but not in genetic studies. To address the impacts of variants in CX3CR1 on neurodevelopmental disorders, we conducted coding exon-targeted resequencing of CX3CR1 in 370 Japanese SCZ and 192 ASD patients using next-generation sequencing technology, followed by a genetic association study in a sample comprising 7054 unrelated individuals (2653 SCZ, 574 ASD and 3827 controls). We then performed in silico three-dimensional (3D) structural modeling and in vivo disruption of Akt phosphorylation to determine the impact of the detected variant on CX3CR1-dependent signal transduction. We detected a statistically significant association between the variant Ala55Thr in CX3CR1 with SCZ and ASD phenotypes (odds ratio=8.3, P=0.020). A 3D structural model indicated that Ala55Thr could destabilize the conformation of the CX3CR1 helix 8 and affect its interaction with a heterotrimeric G protein. In vitro functional analysis showed that the CX3CR1-Ala55Thr mutation inhibited cell signaling induced by fractalkine, the ligand for CX3CR1. The combined data suggested that the variant Ala55Thr in CX3CR1 might result in the disruption of CX3CR1 signaling. Our results strengthen the association between microglia-specific genes and neurodevelopmental disorders.
CX3CR1是一种仅由大脑中的小胶质细胞表达的G蛋白偶联受体，在转录组学和动物研究中，它多次被报道与包括精神分裂症（SCZ）和自闭症谱系障碍（ASD）在内的神经发育障碍有关，但在基因研究中并非如此。为了研究CX3CR1变异对神经发育障碍的影响，我们使用下一代测序技术对370名日本SCZ患者和192名ASD患者进行了CX3CR1编码外显子靶向重测序，随后在一个包含7054名无关个体（2653名SCZ患者、574名ASD患者和3827名对照）的样本中进行了基因关联研究。然后，我们进行了计算机三维（3D）结构建模和体内Akt磷酸化破坏实验，以确定检测到的变异对CX3CR1依赖性信号转导的影响。我们检测到CX3CR1中的Ala55Thr变异与SCZ和ASD表型之间存在统计学上的显著关联（优势比=8.3，P=0.020）。一个3D结构模型表明，Ala55Thr可能会破坏CX3CR1螺旋8的构象，并影响其与异源三聚体G蛋白的相互作用。体外功能分析表明，CX3CR1-Ala55Thr突变抑制了CX3CR1配体fractalkine诱导的细胞信号传导。综合数据表明，CX3CR1中的Ala55Thr变异可能导致CX3CR1信号传导的破坏。我们的结果加强了小胶质细胞特异性基因与神经发育障碍之间的关联。
