Project description:Rett syndrome (RTT) is a severe neurological disorder which is mainly caused by mutations found in the X-linked gene encoding MeCP2. Despite extensive studies, the molecular functions of MeCP2 remain elusive. Here, we report that MeCP2 is a new subunit of a higher-order multiunit protein complex Rbfox/LASR and acts as a scaffold for this splicing complex. Deletion or mutation of MeCP2 leads to defects in forming MeCP2/Rbfox/LASR complex and aberrant alternative pre-mRNA splicing. Our data link RTT to an impaired function of MeCP2 in splicing control through its role in nucleating Rbfox/LASR macromolecule assembly.
Project description:The Rbfox family of splicing factors regulate alternative splicing during animal development and in disease, impacting thousands of exons in the maturing brain, heart, and muscle. Rbfox proteins have long been known to bind to the RNA sequence GCAUG with high affinity, but just half of Rbfox CLIP peaks contain a GCAUG motif. We incubated recombinant RBFOX2 with over 60,000 mouse and human transcriptomic sequences to reveal significant binding to several moderate-affinity, non-GCAYG sites at a physiologically relevant range of RBFOX concentrations. We find that many of these “secondary motifs” bind Rbfox robustly in cells and that several together can exert regulation comparable to a GCAUG in a trichromatic splicing reporter assay. Furthermore, secondary motifs regulate RNA splicing in neuronal development and in neuronal subtypes where cellular Rbfox concentrations are highest, enabling a second wave of splicing changes as Rbfox levels increase.
Project description:To determine how the higher order assembly of Rbfox proteins affect Rbfox-dependent splicing regulation, we expressed Rbfox wildtype and its mutant protein in Flp-In™ T-REx™ 293 Rbfox2-/- cells and extracted RNA from these cells to perform RASL-seq which profiles thousands of alternative splicing event.
Project description:Hypoplastic left heart syndrome (HLHS) is characterized by underdevelopment of left sided structures including the ventricle, valves, and aorta1. Although the mechanisms of disease pathogenesis remain elusive due to a paucity of candidate genes and animal models, prevailing paradigm suggests that HLHS is a multigenic disease of co-occurring phenotypes2,3. Here, we report that zebrafish lacking two orthologs of the RNA binding protein RBFOX2, a gene previously linked to HLHS in humans4,5, display cardiovascular defects overlapping those in HLHS patients. In contrast to current models, we demonstrate that co-existing ventricular, valve, and aortic deficiencies in rbfox mutant zebrafish arise secondary to impaired myocardial function as all three phenotypes are rescued when Rbfox is expressed specifically in the myocardium. On a molecular and cellular level, we find diminished expression and alternative splicing of sarcomere and mitochondrial components in rbfox-deficient hearts that compromise sarcomere assembly and mitochondrial respiration, respectively. Injection of human RBFOX2 mRNA restores ventricular structure and function in rbfox mutant zebrafish, while HLHS-linked RBFOX2 variants fail to rescue. Taken together, our data suggest that mutations in RBFOX2 are causal for HLHS pathogenesis and provide a complimentary paradigm for HLHS emergence where co-existing ventricular, valve, and aortic deficiencies have a monogenic etiology caused by myocardial dysfunction.
Project description:Thymic epithelial cells (TEC) guide selection of a T-cell repertoire that is reactive to pathogens but tolerant to self. While this process is known to involve the promiscuous expression of virtually the entire protein-coding gene repertoire by TEC, the extent to which these cells reproduce peripheral isoform structures is unknown. We performed a transcriptomic investigation of transcript structures and splicing factor expression in medullary TEC and 21 peripheral tissues. Our results indicate that TEC re-use a small number of peripheral splicing factors to recreate a limited subset of the peripheral splice isoform repertoire. We found, for example, that TEC lacked both neuronal microexons and the splicing factor, Srrm4, which promotes their inclusion. We demonstrate a functional role for the Rbfox splicing factors in promoting medullary TEC development and the alternative splicing of promiscuously expressed genes. Our findings have implications for understanding autoimmune diseases and the development of antigen-specific immunotherapies.
