GSE184574
Mice Lacking MBNL1 and MBNL2 Exhibit Sudden Cardiac Death and Molecular Signatures Recapitulating Myotonic Dystrophy
Myotonic dystrophy (dystrophia myotonica, DM) is caused by expansions of CTG (type 1; DM1) or CCTG (type 2; DM2) repeats in the non-coding regions of the DMPK and CNBP genes, and patients with DM1 or DM2 often suffer from sudden cardiac death due to lethal arrhythmia. Specific molecular changes that underlie DM cardiac pathology have been linked to repeat-associated depletion of Muscleblind-like (MBNL) 1 and 2 proteins and upregulation of CUGBP Elav-like family member 1. Aims: We aim to create an Mbnl KO mouse model recapitulating DM cardiogenic death not under anesthesia, since none of the DM mouse models have reached this goal. Besides, it is unclear whether dysfunction of cardiomyocytes, among other cell types in the heart, can solely drive phenotypes. Methods and Results: We generated Myh6-Cre DKO (Mbnl1-/-; Mbnl2cond/cond; Myh6-Cre+/-) mice that completely eliminate Mbnl1/2 expression in cardiomyocytes. In this model, we found increased myocardial fibrosis, dilated cardiomyopathy and various arrhythmias. Importantly, we observed spontaneous lethal arrhythmic events in the context of shortened lifespan. RNA sequencing (RNA-seq) revealed mis-splicing events involving sarcomeric structure, mitochondrial dynamics and vesicular trafficking that mimics DM hearts. Gene expression changes were also noted by RNA-seq, and confirmed by qPCR. Notably, immunoblotting revealed a nearly 6-fold increase of Calsequestrin 1 and 50% reduction of epidermal growth factor proteins. Conclusion: These results showed that complete elimination of MBNL1/2 in mouse cardiomyocytes is sufficient to elicit a full spectrum of DM cardiac phenotypes including cardiac-related sudden death, and therefore these mice could serve as a useful model for studying DM heart pathogenesis and related translational research. Overall design: Myh6-Cre DKO (Mbnl1-/-; Mbnl2cond/cond; Myh6-Cre+/-) mice were generated that lack Mbnl1 and Mbnl2 expression in cardiomyocytes. Hearts were harvested from 3-6 month old mice and subjected to RNA-seq. Strand-specific paired-end RNA sequencing of total RNA was performed using the NEBNext Ultra II Directional Library Prep Kit. Libraries were pooled and sequenced on an Illumina NextSeq 500 v2 instrument using 2x75 paired end reads.