Investigation of the cellular and molecular effects of RELN mutations in Autism Spectrum Disorders.

Abstract

Autism Spectrum Disorders (ASD) are a heterogeneous and highly prevalent group of neurodevelopmental disorders. Whole-genome-based approaches have generated catalogues of thousands of rare and potentially deleterious genetic variants in ASD patients. However, the challenge now is to identify genuine disease-causing/risk variants among the multitude of variants discovered in each exome/genome. This project intends to improve knowledge in this area. Recently, we performed whole-exome sequencing in a subgroup of ASD patients - in whom we found PI3K-mTOR signaling hyperfunction - and identified rare and potentially deleterious missense variants in the RELN gene in one patient (called as F2688). The RELN gene encodes Reelin, a large secreted glycoprotein that controls neuronal migration, layer formation, neurite outgrowth, and plasticity of synapses in both the developing and the adult brain. Evidence from previous studies suggests that certain potential loss-of-function variants in RELN gene can contribute to ASD susceptibility; however, the molecular and cellular effects of these variants in human neuronal cells are still poorly explored. In addition, it is unknown whether these RELN variants can lead to dysfunctional PI3K-mTOR signaling, and whether this mechanism is responsible for the phenotypic alterations in neuronal cells. Therefore, the main goals of this project are to verify whether variants in the RELN gene identified in patients with ASD can lead to morphological and functional abnormalities in human neuronal cells, and whether these alterations are, at least in part, due to dysfunctional PI3K-mTOR signaling pathway. In order to achieve this, we intend to perform detailed functional analyses of neuronal progenitor cells and neurons derived from F2688-specific induced pluripotent stem cells, as well as control-derived neuronal cells engineered to reduce (knockdown) RELN expression. Once these experimental models are established, they can be used to stringently assign causality for other sequence variants identified in ASD patients. (AU)