Sharpe Michka, González-Rosa Juan Manuel, Wranitz Felicia, Jeffrey Spencer, Copenhaver Katherine, Burns C Geoffrey, Burns Caroline E
Division of Basic and Translational Cardiovascular Research, Department of Cardiology, Boston Children's Hospital, Boston, MA, United States.
Cardiovascular Research Center, Massachusetts General Hospital, Charlestown, MA, United States.
Front Cell Dev Biol. 2022 Feb 1;10:800594. doi: 10.3389/fcell.2022.800594. eCollection 2022.
Cardiomyocyte proliferation is an important source of new myocardium during heart development and regeneration. Consequently, mutations in drivers of cardiomyocyte proliferation cause congenital heart disease, and infarcted human hearts scar because cardiomyocytes exit the cell cycle postnatally. To boost cardiomyocyte proliferation in either setting, critical regulators must be identified. Through an ENU screen in zebrafish, the () mutant was isolated and described as having elevated cardiomyocyte numbers during embryogenesis. The mutation results in a three amino acid insertion into Ruvbl2, a highly conserved ATPase. Because both gain- and loss-of-function properties have been described for , it remains unclear whether Ruvbl2 positively or negatively regulates cardiomyocyte proliferation. Here, we demonstrate that Ruvbl2 is a suppressor of cardiomyocyte proliferation during zebrafish heart development and regeneration. First, we confirmed speculation that augmented cardiomyocyte numbers in hearts arise by hyperproliferation. To characterize bona fide null animals, we created a locus deletion allele ( ). Like mutants, and compound heterozygote animals display ventricular hyperplasia, demonstrating that is a loss of function allele and that represses cardiomyocyte proliferation. This activity is autonomous because constitutive myocardial overexpression of Ruvbl2 is sufficient to suppress cardiomyocyte proliferation in control hearts and rescue the hyperproliferation observed in mutant hearts. Lastly, heat-shock inducible overexpression of Ruvbl2 suppresses cardiomyocyte proliferation during heart regeneration and leads to scarring. Together, our data demonstrate that Ruvbl2 functions autonomously as a suppressor of cardiomyocyte proliferation during both zebrafish heart development and adult heart regeneration.
心肌细胞增殖是心脏发育和再生过程中新心肌的重要来源。因此，心肌细胞增殖驱动因子的突变会导致先天性心脏病，而梗死的人类心脏会形成瘢痕，因为心肌细胞在出生后退出细胞周期。为了在这两种情况下促进心肌细胞增殖，必须识别关键调节因子。通过在斑马鱼中进行ENU筛选，分离出了（）突变体，并描述其在胚胎发育过程中心肌细胞数量增加。该突变导致在Ruvbl2（一种高度保守的ATP酶）中插入三个氨基酸。由于已经描述了该突变体的功能获得和功能丧失特性，因此尚不清楚Ruvbl2是正向还是负向调节心肌细胞增殖。在这里，我们证明Ruvbl2在斑马鱼心脏发育和再生过程中是心肌细胞增殖的抑制因子。首先，我们证实了关于突变体心脏中心肌细胞数量增加是由过度增殖引起的推测。为了表征真正的纯合缺失动物，我们创建了一个基因座缺失等位基因（）。与突变体一样，和复合杂合子动物表现出心室增生，表明是功能丧失等位基因，并且抑制心肌细胞增殖。这种活性是自主性的，因为Ruvbl2的组成型心肌过表达足以抑制对照心脏中的心肌细胞增殖，并挽救在突变体心脏中观察到的过度增殖。最后，热休克诱导的Ruvbl2过表达在心脏再生过程中抑制心肌细胞增殖并导致瘢痕形成。总之，我们的数据表明，在斑马鱼心脏发育和成年心脏再生过程中，Ruvbl2作为心肌细胞增殖的抑制因子自主发挥作用。
