Pilorge M, Fassier C, Le Corronc H, Potey A, Bai J, De Gois S, Delaby E, Assouline B, Guinchat V, Devillard F, Delorme R, Nygren G, Råstam M, Meier J C, Otani S, Cheval H, James V M, Topf M, Dear T N, Gillberg C, Leboyer M, Giros B, Gautron S, Hazan J, Harvey R J, Legendre P, Betancur C
INSERM, U1130, Paris, France.
CNRS, UMR 8246, Paris, France.
Mol Psychiatry. 2016 Jul;21(7):936-45. doi: 10.1038/mp.2015.139. Epub 2015 Sep 15.
Autism spectrum disorder (ASD) is a common neurodevelopmental condition characterized by marked genetic heterogeneity. Recent studies of rare structural and sequence variants have identified hundreds of loci involved in ASD, but our knowledge of the overall genetic architecture and the underlying pathophysiological mechanisms remains incomplete. Glycine receptors (GlyRs) are ligand-gated chloride channels that mediate inhibitory neurotransmission in the adult nervous system but exert an excitatory action in immature neurons. GlyRs containing the α2 subunit are highly expressed in the embryonic brain, where they promote cortical interneuron migration and the generation of excitatory projection neurons. We previously identified a rare microdeletion of the X-linked gene GLRA2, encoding the GlyR α2 subunit, in a boy with autism. The microdeletion removes the terminal exons of the gene (GLRA2(Δex8-9)). Here, we sequenced 400 males with ASD and identified one de novo missense mutation, p.R153Q, absent from controls. In vitro functional analysis demonstrated that the GLRA2(Δex8)(-)(9) protein failed to localize to the cell membrane, while the R153Q mutation impaired surface expression and markedly reduced sensitivity to glycine. Very recently, an additional de novo missense mutation (p.N136S) was reported in a boy with ASD, and we show that this mutation also reduced cell-surface expression and glycine sensitivity. Targeted glra2 knockdown in zebrafish induced severe axon-branching defects, rescued by injection of wild type but not GLRA2(Δex8-9) or R153Q transcripts, providing further evidence for their loss-of-function effect. Glra2 knockout mice exhibited deficits in object recognition memory and impaired long-term potentiation in the prefrontal cortex. Taken together, these results implicate GLRA2 in non-syndromic ASD, unveil a novel role for GLRA2 in synaptic plasticity and learning and memory, and link altered glycinergic signaling to social and cognitive impairments.
自闭症谱系障碍（ASD）是一种常见的神经发育疾病，其特征为显著的遗传异质性。近期对罕见结构和序列变异的研究已鉴定出数百个与ASD相关的基因座，但我们对整体遗传结构和潜在病理生理机制的了解仍不完整。甘氨酸受体（GlyRs）是配体门控氯离子通道，在成人神经系统中介导抑制性神经传递，但在未成熟神经元中发挥兴奋性作用。含有α2亚基的GlyRs在胚胎大脑中高度表达，在那里它们促进皮质中间神经元迁移和兴奋性投射神经元的产生。我们之前在一名自闭症男孩中鉴定出X连锁基因GLRA2（编码GlyR α2亚基）的罕见微缺失。该微缺失去除了基因的末端外显子（GLRA2(Δex8-9)）。在此，我们对400名患有ASD的男性进行测序，鉴定出一个对照组中不存在的新生错义突变p.R153Q。体外功能分析表明，GLRA2(Δex8)(-)(9)蛋白未能定位于细胞膜，而R153Q突变损害了表面表达并显著降低了对甘氨酸的敏感性。最近，在一名患有ASD的男孩中报道了另一个新生错义突变（p.N136S），我们发现该突变也降低了细胞表面表达和甘氨酸敏感性。在斑马鱼中靶向敲低glra2会诱导严重的轴突分支缺陷，注射野生型转录本可挽救该缺陷，但注射GLRA2(Δex8-9)或R153Q转录本则不能，这为它们的功能丧失效应提供了进一步证据。Glra2基因敲除小鼠在物体识别记忆方面存在缺陷，前额叶皮质的长期增强也受损。综上所述，这些结果表明GLRA2与非综合征性ASD有关，揭示了GLRA2在突触可塑性以及学习和记忆中的新作用，并将改变的甘氨酸能信号与社交和认知障碍联系起来。
