Genetic and functional analyses demonstrate a role for abnormal glycinergic signaling in autism

• Published in: Molecular psychiatry Vol. 21; no. 7; pp. 936 - 945
• Main Authors: 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
• Format: Journal Article
• Language: English
• Published: London Nature Publishing Group UK 01.07.2016; Nature Publishing Group; Nature Publishing Group Specialist Journals
• Subjects: 14; 45/23; 45/61; 45/70; 45/77; 631/208; 631/337; 631/378; 64/110; 64/116; 692/699/476/1373; Adolescent; Adult; Analysis; Animals; Autism; Autism Spectrum Disorder - metabolism; Autistic Disorder - metabolism; Behavioral Sciences; Biological Psychology; Cell membranes; Cell surface; Child; Child, Preschool; Chloride channels; Cognitive ability; Danio rerio; Embryos; Exons; Genetic analysis; Genetic aspects; Genetics; Glycine - genetics; Glycine - metabolism; Glycine receptors; Human health and pathology; Humans; Life Sciences; Long-term potentiation; Long-Term Potentiation - drug effects; Male; Medicine; Medicine & Public Health; Memory; Mice; Mice, Inbred C57BL; Missense mutation; Mutation; Nervous system; Neurogenesis - drug effects; Neuronal Plasticity - drug effects; Neurons - metabolism; Neurons and Cognition; Neurosciences; Neurotransmission; original-article; Pattern recognition; Pharmacotherapy; Physiology, Pathological; Prefrontal cortex; Psychiatrics and mental health; Psychiatry; Psykiatri; Receptors, Glycine - genetics; Receptors, Glycine - metabolism; Signal Transduction - drug effects; Synaptic plasticity; Synaptic Transmission - physiology; Zebrafish; rare variants; Morris water maze; de novo; prefrontal cortex; functional analysis; X chromosome; α2 subunit; repetitive behaviors; axon branching; whole-cell recording; sequencing; rescue analyses; GLRA2; glycine receptor; deletion; mutation screening; social interaction; immunohistochemistry; knock-out mice; rotarod; long term potentiation; site-directed mutagenesis; biotinylation; glycinergic signaling; novel object recognition; loss of function; Autism spectrum disorder; excitatory-inhibitory imbalance; mutation; microarray; language delay; learning and memory; electrophysiology; interneuron; locomotor activity; synaptic plasticity; zebrafish; intellectual disability
• ISSN: 1359-4184; 1476-5578; 1476-5578
• DOI: 10.1038/mp.2015.139

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.