Abstract
CircRNAs are an evolutionarily conserved class of RNAs produced by a process named back-splicing to form covalently closed loop structures lacking 3’ & 5’ ends. Recent reports emphasize the role of a subset of circRNAs in gene regulation likely by binding and sponging miRNAs, and their ability to get translated in neural tissues. Moreover, there have been increased reports on the biogenesis of circRNAs. The Kadener lab showed that circRNA biogenesis competes with pre-mRNA splicing. This is particularly evident in the muscleblind (mbl) locus. For example, in Drosophila S2 cell lines MBL itself facilitates the circularization of its own 2nd exon to produce circMbl. MBL binds to several binding sites on the flanking introns and 2nd exon of mbl pre-mRNA. Out of many isoforms produced from mbl locus, MBL-A and MBL-C, specifically facilitates the biogenesis of circMbl. This thesis demonstrates the differential regulation of circMbl biogenesis in vivo by the overexpression of different mbl isoforms ubiquitously and locally in fly neurons using Gal4-UAS system. Additionally, there have been reports on the role of MBL in muscular dystrophy due to RNA toxicity caused by the expression of CTG repeats. It has been reported that MBL is sequestered by the CTG repeats and form nuclear foci. This thesis also demonstrates how circMbl expression is regulated in Myotonic Dystrophy models in Drosophila alongside characterizing the subcellular localization of mbl-A, mbl-B and mbl-C isoforms in S2 cells and in MD1 models.