Methylomic analysis of monozygotic twins discordant for autism spectrum disorder and related behavioural traits

Autism spectrum disorder (ASD) defines a group of common, complex neurodevelopmental disorders. Although the aetiology of ASD has a strong genetic component, there is considerable monozygotic (MZ) twin discordance indicating a role for non-genetic factors. Because MZ twins share an identical DNA sequence, disease-discordant MZ twin pairs provide an ideal model for examining the contribution of environmentally driven epigenetic factors in disease. We performed a genome-wide analysis of DNA methylation in a sample of 50 MZ twin pairs (100 individuals) sampled from a representative population cohort that included twins discordant and concordant for ASD, ASD-associated traits and no autistic phenotype. Within-twin and between-group analyses identified numerous differentially methylated regions associated with ASD. In addition, we report significant correlations between DNA methylation and quantitatively measured autistic trait scores across our sample cohort. This study represents the first systematic epigenomic analyses of MZ twins discordant for ASD and implicates a role for altered DNA methylation in autism

An AUTS2–Polycomb complex activates gene expression in the CNS

Naturally occurring variations of Polycomb Repressive Complex 1 (PRC1) comprise a core assembly of Polycomb group proteins and additional factors that include, surprisingly, Autism Susceptibility Candidate 2 (AUTS2). While AUTS2 is often disrupted in patients with neuronal disorders, the underlying mechanism is unclear. We investigated the role of AUTS2 as part of a previously identified PRC1 complex (PRC1-AUTS2), and in the context of neurodevelopment. In contrast to the canonical role of PRC1 in gene repression, PRC1-AUTS2 activates transcription. Biochemical studies demonstrated that the CK2 component of PRC1-AUTS2 thwarts PRC1 repressive activity while AUTS2-mediated recruitment of P300 leads to gene activation. ChIP-seq demonstrated that AUTS2 regulates neuronal gene expression through promoter association. Conditional targeting of Auts2 in the mouse central nervous system (CNS) leads to various developmental defects. These findings reveal a natural means of subverting PRC1 activity, linking key epigenetic modulators with neuronal functions and diseases