CRISPR -Mediated Expression of the Fetal Scn5a Isoform in Adult Mice Causes Conduction Defects and Arrhythmias.
Background The sodium channel, Nav1.5, encoded by SCN 5A, undergoes developmentally regulated splicing from inclusion of exon 6A in the fetal heart to exon 6B in adults. These mutually exclusive exons differ in 7 amino acids altering the electrophysiological properties of the Nav1.5 channel. In myotonic dystrophy type 1, SCN 5A is mis-spliced such that the fetal pattern of exon 6A inclusion is detected in adult hearts. Cardiac manifestations of myotonic dystrophy type 1 include conduction defects and arrhythmias and are the second-leading cause of death. Methods and Results This work aimed to determine the impact of SCN 5A mis-splicing on cardiac function. We used clustered regularly interspaced short palindromic repeat ( CRISPR) /CRISPR-associated protein 9 (Cas9) to delete Scn5a exon 6B in mice, thereby redirecting splicing toward exon 6A. These mice exhibit prolonged PR and QRS intervals, slowed conduction velocity, extended action potential duration, and are highly susceptible to arrhythmias. Conclusions Our findings highlight a nonmutational pathological mechanism of arrhythmias and conduction defects as a result of mis-splicing of the predominant cardiac sodium channel. Animals homozygous for the deleted exon express only the fetal isoform and have more-severe phenotypes than heterozygotes that also express the adult isoform. This observation is directly relevant to myotonic dystrophy type 1, and possibly pathological arrhythmias, in which individuals differ with regard to the ratios of the isoforms expressed.
['Pang|Paul D|PD|', 'Alsina|Katherina M|KM|', 'Cao|Shuyi|S|', 'Koushik|Amrita B|AB|', 'Wehrens|Xander H T|XHT|', 'Cooper|Thomas A|TA|']
D000483:Alleles D000818:Animals D001145:Arrhythmias, Cardiac D064112:Clustered Regularly Interspaced Short Palindromic Repeats D004195:Disease Models, Animal D004562:Electrocardiography D005260:Female D018507:Gene Expression Regulation, Developmental D006329:Heart Conduction System D008297:Male D051379:Mice D008822:Mice, Transgenic D062554:NAV1.5 Voltage-Gated Sodium Channel D010641:Phenotype D011247:Pregnancy D011270:Pregnancy, Animal D012313:RNA
SCN5A conduction arrhythmia alternative splicing myotonic dystrophy cardiomyopathy