HNRNPA1-induced spliceopathy in a transgenic mouse model of myotonic dystrophy

• Published in: Proceedings of the National Academy of Sciences - PNAS Vol. 117; no. 10; pp. 5472 - 5477
• Main Authors: Li, Moyi, Zhuang, Yan, Batra, Ranjan, Thomas, James D., Li, Mao, Nutter, Curtis A., Scotti, Marina M., Carter, Helmut A., Wang, Zhan Jun, Huang, Xu-Sheng, Pu, Chuan Qiang, Swanson, Maurice S., Xie, Wei
• Format: Journal Article
• Language: English
• Published: United States National Academy of Sciences 10.03.2020
• Subjects: Alternative splicing; Biocompatibility; Biological Sciences; Dystrophy; Fetuses; Gene expression; In vivo methods and tests; Isoforms; Model testing; Muscles; Myoblasts; Myopathy; Myotonic dystrophy; Proteins; Reversion; RNA processing; RNA-binding protein; Rodents; Skeletal muscle; Splicing; Splicing factors; Transgenic mice; Viruses; microsatellite; MBNL1; splicing; HNRNPA1; CELF1
• ISSN: 0027-8424; 1091-6490
• DOI: 10.1073/pnas.1907297117

Studies on myotonic dystrophy type 1 (DM1) have led to the RNA-mediated disease model for hereditary disorders caused by noncoding microsatellite expansions. This model proposes that DM1 disease manifestations are caused by a reversion to fetal RNA processing patterns in adult tissues due to the expression of toxic CUG RNA expansions (CUGexp) leading to decreased muscleblind-like, but increased CUGBP1/ETR3-like factor 1 (CELF1), alternative splicing activities. Here, we test this model in vivo, using the mouse HSA LR poly(CUG) model for DM1 and recombinant adeno-associated virus (rAAV)-mediated transduction of specific splicing factors. Surprisingly, systemic overexpression of HNRNPA1, not previously linked to DM1, also shifted DM1-relevant splicing targets to fetal isoforms, resulting in more severe muscle weakness/myopathy as early as 4 to 6 wk posttransduction, whereas rAAV controls were unaffected. Overexpression of HNRNPA1 promotes fetal exon inclusion of representative DM1-relevant splicing targets in differentiated myoblasts, and HITS-CLIP of rAAV-mycHnrnpa1-injected muscle revealed direct interactions of HNRNPA1 with these targets in vivo. Similar to CELF1, HNRNPA1 protein levels decrease during postnatal development, but are elevated in both regenerating mouse muscle and DM1 skeletal muscle. Our studies suggest that CUGexp RNA triggers abnormal expression of multiple nuclear RNA binding proteins, including CELF1 and HNRNPA1, that antagonize MBNL activity to promote fetal splicing patterns.