The Characterization of GSDMB Splicing and Backsplicing Profiles Identifies Novel Isoforms and a Circular RNA That Are Dysregulated in Multiple Sclerosis

Abstract

Abnormalities in alternative splicing (AS) are emerging as recurrent features in autoimmune diseases (AIDs). In particular, a growing body of evidence suggests the existence of a pathogenic association between a generalized defect in splicing regulatory genes and multiple sclerosis (MS). Moreover, several studies have documented an unbalance in alternatively-spliced isoforms in MS patients possibly contributing to the disease etiology. In this work, using a combination of PCR-based techniques (reverse-transcription (RT)-PCR, fluorescent-competitive, real-time, and digital RT-PCR assays), we investigated the alternatively-spliced gene encoding Gasdermin B, <i>GSDMB</i>, which was repeatedly associated with susceptibility to asthma and AIDs. The in-depth characterization of <i>GSDMB</i> AS and backsplicing profiles led us to the identification of an exonic circular RNA (ecircRNA) as well as of novel <i>GSDMB</i> in-frame and out-of-frame isoforms. The non-productive splicing variants were shown to be downregulated by the nonsense-mediated mRNA decay (NMD) in human cell lines, suggesting that <i>GSDMB</i> levels are significantly modulated by NMD. Importantly, both AS isoforms and the identified ecircRNA were significantly dysregulated in peripheral blood mononuclear cells of relapsing-remitting MS patients compared to controls, further supporting the notion that aberrant RNA metabolism is a characteristic feature of the disease.