Impact of MYH6 variants in hypoplastic left heart syndrome.

Aoy Tomita-Mitchell,Huan Ling Liang,Min-Su Kim,Pip M Hidestrand,D Woodrow Benson,Karl D Stamm,Michael E Mitchell,James S Tweddell,Andrew N Pelech,Mats Hidestrand,Donna K Mahnke,Pippa Simpson,John W Lough,Mary A Goetsch

doi:10.1152/physiolgenomics.00091.2016

Abstract

Hypoplastic left heart syndrome (HLHS) is a clinically and anatomically severe form of congenital heart disease (CHD). Although prior studies suggest that HLHS has a complex genetic inheritance, its etiology remains largely unknown. The goal of this study was to characterize a risk gene in HLHS and its effect on HLHS etiology and outcome. We performed next-generation sequencing on a multigenerational family with a high prevalence of CHD/HLHS, identifying a rare variant in the α-myosin heavy chain (MYH6) gene. A case-control study of 190 unrelated HLHS subjects was then performed and compared with the 1000 Genomes Project. Damaging MYH6 variants, including novel, missense, in-frame deletion, premature stop, de novo, and compound heterozygous variants, were significantly enriched in HLHS cases (P < 1 × 10−5). Clinical outcomes analysis showed reduced transplant-free survival in HLHS subjects with damaging MYH6 variants (P < 1 × 10−2). Transcriptome and protein expression analyses with cardiac tissue revealed differential expression of cardiac contractility genes, notably upregulation of the β-myosin heavy chain (MYH7) gene in subjects with MYH6 variants (P < 1 × 10−3). We subsequently used patient-specific induced pluripotent stem cells (iPSCs) to model HLHS in vitro. Early stages of in vitro cardiomyogenesis in iPSCs derived from two unrelated HLHS families mimicked the increased expression of MYH7 observed in vivo (P < 1 × 10−2), while revealing defective cardiomyogenic differentiation. Rare, damaging variants in MYH6 are enriched in HLHS, affect molecular expression of contractility genes, and are predictive of poor outcome. These findings indicate that the etiology of MYH6-associated HLHS can be informed using iPSCs and suggest utility in future clinical applications.

Highlights

HYPOPLASTIC LEFT HEART SYNDROME (HLHS) accounts for as much as 4% of subjects with congenital heart disease (CHD) but is responsible for 15–25% of CHD-related mortality [3]
myosin heavy chain 6 (MYH6) variants have been previously associated with cardiac phenotypes [1, 4, 6, 12, 33, 38], to better understand their role in HLHS we have employed a multifaceted approach including a case-control association study, transcriptome analysis of patient cardiac tissue, clinical outcomes, and the use of patient-specific induced pluripotent stem cells to model HLHS disease in vitro
A five-stage approach was employed to elucidate the role of MYH6 variants in HLHS

Summary

Introduction

HLHS accounts for as much as 4% of subjects with CHD but is responsible for 15–25% of CHD-related mortality [3]. Increased frequency of left-ventricular outflow tract obstructions (LVOTO) such as bicuspid aortic valve (BAV) and coarctation of the aorta (CoA) have been noted in relatives of HLHS subjects [16, 17, 23, 24, 29]. These studies indicate an underlying genetic basis, known risk factors currently explain Ͻ5% of HLHS etiology [16, 17]. Experiments using patient-derived cardiomyocytes indicate that HLHS may have a cardiomyocyteautonomous etiology that can be investigated via in vitro modeling with iPSCs

Objectives

Results

Conclusion