Identification of MYLK3 mutations in familial dilated cardiomyopathy

Takashige Tobita,Kenta Uto,Haruhiro Toko,Seitaro Nomura,Takanori Fujita,Hiroyuki Aburatani,Issei Komuro,Toshiyuki Ko,Hiroyuki Morita,Nobuhisa Hagiwara

doi:10.1038/s41598-017-17769-1

Abstract

Dilated cardiomyopathy (DCM) is a primary cause of heart failure, life-threatening arrhythmias, and cardiac death. Pathogenic mutations have been identified at the loci of more than 50 genes in approximately 50% of DCM cases, while the etiologies of the remainder have yet to be determined. In this study, we applied whole exome sequencing in combination with segregation analysis to one pedigree with familial DCM, and identified a read-through mutation (c.2459 A > C; p.*820Sext*19) in the myosin light chain kinase 3 gene (MYLK3). We then conducted MYLK3 gene screening of 15 DCM patients (7 familial and 8 sporadic) who were negative for mutation screening of the previously-reported cardiomyopathy-causing genes, and identified another case with a MYLK3 frameshift mutation (c.1879_1885del; p.L627fs*41). In vitro experiments and immunohistochemistry suggested that the MYLK3 mutations identified in this study result in markedly reduced levels of protein expression and myosin light chain 2 phosphorylation. This is the first report that MYLK3 mutations can cause DCM in humans. The clinical phenotypes of DCM patients were consistent with MYLK3 loss-of-function mouse and zebrafish models in which cardiac enlargement and heart failure are observed. Our findings highlight an essential role for cardiac myosin light chain kinase in the human heart.

Highlights

Dilated cardiomyopathy (DCM) is a genetic disorder that causes heart failure, life- threatening arrhythmias, and cardiac death[1]
We identified two mutations in myosin light chain kinase 3 (MYLK3) that were associated with human DCM pathogenesis
The importance of Cardiac myosin light chain kinase (cMLCK) for proper cardiac function is strongly suggested by animal cardiomyopathy models in vivo and experimental data in vitro[4,5,7], no MYLK3 mutation has been identified as a pathogenic factor of human cardiomyopathy

Summary

Introduction

Dilated cardiomyopathy (DCM) is a genetic disorder that causes heart failure, life- threatening arrhythmias, and cardiac death[1]. Whole exome sequencing (WES) has been used successfully to identify genetic abnormalities in relatively rare hereditary diseases[3]. Cardiac myosin light chain kinase (cMLCK) encoded by the myosin light chain kinase 3 (MYLK3) phosphorylates cardiac myosin light chain 2 (MLC2, encoded by MYL2) and facilitates actin−myosin interactions that enhance contractile force in the animal heart[4,5,6]. MYLK3 loss-of-function in mice and zebrafish induced cardiac dysfunction and heart failure[4,7], suggesting that this kinase is indispensable for cardiac homeostasis. We report the first DCM cases harboring MYLK3 mutations identified using WES. Sequencing analyses of unrelated DCM patients revealed an additional MYLK3 frameshift mutation. Our human genetic analysis suggests that MYLK3 is a novel pathogenic gene for DCM

Methods

Results

Conclusion