Dottorato in GENETICA E BIOLOGIA MOLECOLARE

Titolo della tesi: Differential expression of circular RNAs in a mouse model of autism spectrum disorders

Autism spectrum disorder (ASD) comprises a heterogeneous group of pervasive developmental disabilities characterized by compromised social interactions and communication skills, and by restrictive and repetitive behaviors. Emerging evidence suggests the involvement of non-coding RNAs (ncRNAs) in the pathophysiology of ASD. circRNAs arisen in the last decades as a novel class of ncRNAs and recent reports have shown their implication in the pathogenesis of several human neurological diseases. circRNAs are endogenous stable molecules, characterized by a covalently closed structure resulting from a backpslicing reaction. They are evolutionary conserved, abundant and significantly enriched in the brain. Although the biological function is still unknown, specific circRNAs are regulated by neuronal activity and have been implicated in plasticity mechanisms. In this study, we present the expression profile of circRNAs in the hippocampus of BTBR T + tf/J (BTBR) mouse model for Autism Spectrum Disorder (ASD), compared to age-matched C57BL/6J (B6) mice. We identified several circRNAs whose expression is consistently altered, and 12 circRNAs and their corresponding linear counterparts were validated by RT-qPCR analysis. The ASD-related circCdh9 and circRmst have been further characterized in terms of molecular structure and expression. To evaluate their functional role in a physiological context, we characterized their expression during mouse development, neuronal differentiation and homeostatic plasticity. Interestingly, our results suggest a possible involvement of circCdh9 and circRmst in brain development and neuronal differentiation. Moreover, to comprehensively investigate the transcriptomic profile of the hippocampus of BTBR mice, we analyzed the gene and miRNA expression patterns. We performed enrichment analysis of BTBR differentially expressed RNA species and found interesting biological and molecular pathways associated to ASD phenotype. Lastly, we compared the circRNAs and gene expression profiles and we identified 6 genes highly modulated as circular and linear isoforms, indicative of a low correlation in the expression of circRNAs and their host genes. In conclusion, our study has identified and analyzed differentially expressed circRNAs in the BTBR hippocampus, and we deepen characterized two ASD-associated circRNAs candidates. By integrating the circRNAs and gene expression profiles, we found a coregulation in the expression of specific genes ASD related. Moreover, we explored for the first time the miRNA expression profile in the hippocampus of BTBR mice, and we found 18 significantly modulated miRNAs. Functional studies are in progress to shed more light on the physiological function of circCdh9 and circRmst and their putative role in the pathophysiology of ASD.