Department of Biochemistry and Molecular Biology, Department of Cardiovascular Medicine, Mayo Clinic, Rochester, Minnesota, USA.
Department of Cardiothoracic Surgery, Xiangya Hospital, Central South University, Changsha, China.
JCI Insight. 2021 Dec 22;6(24):e154215. doi: 10.1172/jci.insight.154215.
Myosin heavy chain 7 (MYH7) is a major causative gene for hypertrophic cardiomyopathy, but the affected signaling pathways and therapeutics remain elusive. In this research, we identified ventricle myosin heavy chain like (vmhcl) as a zebrafish homolog of human MYH7, and we generated vmhcl frameshift mutants. We noted vmhcl-based embryonic cardiac dysfunction (VEC) in the vmhcl homozygous mutants and vmhcl-based adult cardiomyopathy (VAC) phenotypes in the vmhcl heterozygous mutants. Using the VEC model, we assessed 7 known cardiomyopathy signaling pathways pharmacologically and 11 candidate genes genetically via CRISPR/Cas9 genome editing technology based on microhomology-mediated end joining (MMEJ). Both studies converged on therapeutic benefits of mTOR or mitogen-activated protein kinase (MAPK) inhibition of VEC. While mTOR inhibition rescued the enlarged nuclear size of cardiomyocytes, MAPK inhibition restored the prolonged cell shape in the VEC model. The therapeutic effects of mTOR and MAPK inhibition were later validated in the VAC model. Together, vmhcl/myh7 loss of function is sufficient to induce cardiomyopathy in zebrafish. The VEC and VAC models in zebrafish are amenable to both efficient genetic and chemical genetic tools, offering a rapid in vivo platform for discovering candidate signaling pathways of MYH7 cardiomyopathy.
肌球蛋白重链 7（MYH7）是肥厚型心肌病的主要致病基因，但相关的信号通路和治疗方法仍不明确。在这项研究中，我们鉴定了心室肌球蛋白重链样（vmhcl）是人类 MYH7 的斑马鱼同源物，并生成了 vmhcl 移码突变体。我们观察到 vmhcl 纯合突变体的胚胎心脏功能障碍（VEC）和 vmhcl 杂合突变体的成年心肌病（VAC）表型。利用 VEC 模型，我们通过 CRISPR/Cas9 基因组编辑技术基于微同源介导的末端连接（MMEJ）对 7 种已知的心肌病信号通路进行了药理学评估，并对 11 种候选基因进行了遗传学评估。这两项研究都集中在 mTOR 或丝裂原活化蛋白激酶（MAPK）抑制 VEC 的治疗益处上。虽然 mTOR 抑制挽救了心肌细胞增大的核大小，但 MAPK 抑制恢复了 VEC 模型中延长的细胞形状。mTOR 和 MAPK 抑制的治疗效果后来在 VAC 模型中得到了验证。总之，vmhcl/myh7 功能丧失足以在斑马鱼中诱导心肌病。斑马鱼中的 VEC 和 VAC 模型适用于高效的遗传和化学遗传工具，为发现 MYH7 心肌病的候选信号通路提供了一个快速的体内平台。
