Common and rare variants of microRNA genes in autism spectrum disorders.

Objectives. MicroRNAs (miRNAs) are post-transcriptional regulators that have been shown to be involved in disease susceptibility. Here we explore the possible contribution of common and rare variants in miRNA genes in autism spectrum disorders (ASD). Methods. A total of 350 tag SNPs from 163 miRNA genes were genotyped in 636 ASD cases and 673 controls. A replication study was performed in a sample of 449 ASD cases and 415 controls. Additionally, rare variants in 701 miRNA genes of 41 ASD patients were examined using whole-exome sequencing. Results. The most signifi cant association in the discovery sample was obtained for the miR-133b/miR-206 cluster (rs16882131, P � 0.00037). The replication study did not reach signifi cance. However, the pooled analysis (1,085 cases and 1,088 controls) showed association with two miRNA clusters: miR-133b/miR-206 (rs16882131, permP � 0.037) and miR-17/miR-18a/miR-19a/miR-20a/miR19b-1/miR92a-1 (rs6492538, permP � 0.019). Both miR-133b and miR-206 regulate the MET gene, previously associated with ASD. Rare variant analysis identifi ed mutations in several miRNA genes, among them miR-541, a brain-specifi c miRNA that regulates SYN1 , found mutated in ASD. Conclusions. Although our results do not establish a clear role for miRNAs in ASD, we pinpointed a few candidate genes. Further exome and GWAS studies are warranted to get more insight into their potential contribution to the disorder.