Characterization of a neuronal circular RNA associated with Autism

Circular RNAs (circRNAs) are covalently closed RNA molecules generated by a non-canonical splicing event called backsplicing. They have recently been identified as key regulators of gene expression, acting as sponges or scaffolds for microRNAs and RNA-binding proteins (RBPs). circRNAs are highly abundant in the nervous system and are involved in neuronal differentiation and nervous system development. Recent experimental evidence suggests their role in the etiology of several human neurodevelopmental and neurological diseases. A previous study from our laboratory identified circRNAs differentially expressed in the hippocampus of BTBR mice, a mouse model for idiopathic Autism Spectrum Disorders (ASD) (Gasparini et al., 2020). The present study focuses on the molecular and functional characterization in neuronal mouse model systems of one ASD-related circRNA, namely circCacna1c. circCacna1c expression is analyzed during neuronal differentiation of in vitro primary cultures of mouse cortical neurons (CNs), and during prenatal and postnatal mouse brain development. Functional studies are performed in CNs by knockdown experiments with circRNA-specific siRNAs. To identify potential circCacna1c interactors, we performed a bioinformatic analysis that revealed as potential binders, RBPs involved in neuronal differentiation and alternative splicing, including ASD-relevant SFARI genes. The binding of circCacna1c with the best candidate interactor is analyzed by RNA immunoprecipitation experiments. A broad proteomic analysis of brain interactors pulled down by circCacna1c is currently ongoing. Our findings will provide molecular insights into the function of circCacna1c under physiological conditions, clarifying its potential contribution to ASD.