SA94 - A DIRECT REGULATORY LINK BETWEEN MICRORNA MIR-137 AND SHANK2 WITH IMPLICATIONS FOR NEUROPSYCHIATRIC DISORDERS

Abstract

Background The SHANK gene family encodes for postsynaptic scaffolding proteins with an important role at glutamatergic synapses in the brain and has been linked to a spectrum of neurodevelopmental disorders. The schizophrenia associated microRNA miR-137 and the SHANK genes converge on several levels, (a) both are expressed at the synapse, (b) both influence neuronal development, and (c) both have a strong link to neurodevelopmental and neuropsychiatric disorders like intellectual disability, autism and schizophrenia. This compiled evidence raised the question if the SHANKs might be targets of miR-137. Methods The in silico analysis of all three SHANK genes identified a single, highly conserved binding site for miR-137 in the 3´UTR of SHANK2. Luciferase assays were carried out in a neuroblastoma cell line (SH-SY5Y) and in mouse primary hippocampal neurons to validate the putative binding site. MiR-137 was overexpressed or inhibited in hippocampal neurons and Shank2 expression was analyzed by qPCR and Western blot. In addition, we analyzed expression levels of experimentally validated miR-137 target genes in the dorsolateral prefrontal cortex (DLPFC) of schizophrenia and control individuals using the RNA-seq data from the CommonMind Consortium. Results We can show that miR-137 targets the 3´UTR of SHANK2 in a site-specific manner. Overexpression of miR-137 significantly lowered endogenous Shank2 protein levels without detectable influence on mRNA level; conversely, the inhibition of miR-137 resulted in the increase of Shank2 protein in neuronal cells. To further support the link between miR-137 and schizophrenia, we compared the expression of mir-137 precursor and miR-137 target genes (including SHANK2) in the DLPFC of schizophrenia and control individuals. Almost one third (18/63; 29%) of validated miR-137 target genes showed significant expression differences in the DLPFC of schizophrenia individuals compared to controls and we propose that further targets (like SHANK2) may be regulated on protein level. Discussion In this study we identified SHANK2 as a novel direct target of miR-137. We discovered that physiological levels of miR-137 regulate SHANK2 expression and that the most likely mechanism of microRNA-mediated regulation is by repressing SHANK2 protein translation rather than mRNA degradation. Our study provides first evidence of a direct regulatory link between miR-137 and SHANK2 and supports the finding that miR-137 signaling is altered in schizophrenia.