Mutation of the histone demethylase Gasc1 causes ASD-like symptoms in mice

Background: Genomic analyses of psychiatric disorders, including autism spectrum disorder (ASD), have revealed many susceptibility genes, suggesting that such disorders may be caused by multiple factors. In this sense, it has long been a question whether there is an abnormal genetic status that comprehensively explains the pathogenesis of neuropsychiatric disorders or a"promising upstream treatment target"that normalizes symptoms. Methods: To address this question, we provide important clues with respect to GASC1 (JMJD2 C/KDM4 C), which is a histone demethylase that prominently targets trimethylated histone H3 at lysine 9 (H3 K9 me3). Gasc1 hypomorphic mutant mice were analyzed using molecular biological, biochemical, behavioral battery tests, histological, and electrophysiological techniques. Results: Mice homozygous for a hypomorphic mutation in Gasc1 exhibited abnormal behaviors, including hyperactivity, stereotyped behaviors, and impaired learning and memory, which are reminiscent of those of human psychiatric disorders. Electrophysiological studies of hippocampal slices revealed decreased paired-pulse facilitation and enhanced long-term potentiation, suggesting synaptic dysfunction in the mutants. Increased dendritic spine density in CA1 neurons was also detected in the mutants. Intriguingly, genetic linkage studies of human ASD have mapped a susceptibility locus on chromosome 9p24.1, which contains 78 genes, including the GASC1 gene. Conclusion: Taken together, our data suggest that histone demethylation plays a pivotal role in normal brain development and higher-order brain functions in both mice and humans.