Center for Genetic Medicine, Feinberg School of Medicine, Northwestern University, Chicago, IL, United States of America; Department of Cell and Molecular Physiology, Loyola University Chicago, Maywood, IL, United States of America.
Center for Genetic Medicine, Feinberg School of Medicine, Northwestern University, Chicago, IL, United States of America.
J Mol Cell Cardiol. 2022 Aug;169:28-40. doi: 10.1016/j.yjmcc.2022.04.012. Epub 2022 May 6.
A premature truncation of MYBPHL in humans and a loss of Mybphl in mice is associated with dilated cardiomyopathy, atrial and ventricular arrhythmias, and atrial enlargement. MYBPHL encodes myosin binding protein H-like (MyBP-HL). Prior work in mice indirectly identified Mybphl expression in the atria and in small puncta throughout the ventricle. Because of its genetic association with human and mouse cardiac conduction system disease, we evaluated the anatomical localization of MyBP-HL and the consequences of loss of MyBP-HL on conduction system function. Immunofluorescence microscopy of normal adult mouse ventricles identified MyBP-HL-positive ventricular cardiomyocytes that co-localized with the ventricular conduction system marker contactin-2 near the atrioventricular node and in a subset of Purkinje fibers. Mybphl heterozygous ventricles had a marked reduction of MyBP-HL-positive cells compared to controls. Lightsheet microscopy of normal perinatal day 5 mouse hearts showed enrichment of MyBP-HL-positive cells within and immediately adjacent to the contactin-2-positive ventricular conduction system, but this association was not apparent in Mybphl heterozygous hearts. Surface telemetry of Mybphl-null mice revealed atrioventricular block and atrial bigeminy, while intracardiac pacing revealed a shorter atrial relative refractory period and atrial tachycardia. Calcium transient analysis of isolated Mybphl-null atrial cardiomyocytes demonstrated an increased heterogeneity of calcium release and faster rates of calcium release compared to wild type controls. Super-resolution microscopy of Mybphl heterozygous and homozygous null atrial cardiomyocytes showed ryanodine receptor disorganization compared to wild type controls. Abnormal calcium release, shorter atrial refractory period, and atrial dilation seen in Mybphl null, but not wild type control hearts, agree with the observed atrial arrhythmias, bigeminy, and atrial tachycardia, whereas the proximity of MyBP-HL-positive cells with the ventricular conduction system provides insight into how a predominantly atrial expressed gene contributes to ventricular arrhythmias and ventricular dysfunction.
人类中 MYBPHL 的过早截短和小鼠中 Mybphl 的缺失与扩张型心肌病、心房和心室心律失常以及心房扩大有关。MYBPHL 编码肌球蛋白结合蛋白 H 样（MyBP-HL）。先前在小鼠中的研究工作间接确定了 Mybphl 在心房和心室中的小斑点中的表达。由于其与人类和小鼠心脏传导系统疾病的遗传关联，我们评估了 MyBP-HL 的解剖定位以及缺失 MyBP-HL 对传导系统功能的影响。正常成年小鼠心室的免疫荧光显微镜鉴定出 MyBP-HL 阳性的心室肌细胞，这些细胞与房室结附近的心室传导系统标志物接触蛋白-2以及一部分浦肯野纤维共定位。与对照组相比，Mybphl 杂合子心室中的 MyBP-HL 阳性细胞数量明显减少。正常围产期第 5 天小鼠心脏的光片显微镜显示，MyBP-HL 阳性细胞在接触蛋白-2 阳性心室传导系统内及其附近富集，但在 Mybphl 杂合子心脏中这种关联并不明显。Mybphl 缺失小鼠的体表遥测显示房室传导阻滞和心房二联律，而心内起搏显示心房相对不应期缩短和心房心动过速。分离的 Mybphl 缺失心房肌细胞的钙瞬变分析表明，与野生型对照相比，钙释放的异质性增加，钙释放速度加快。Mybphl 杂合子和纯合子缺失心房肌细胞的超分辨率显微镜显示，与野生型对照相比，兰尼碱受体的组织紊乱。Mybphl 缺失但不是野生型对照心脏中观察到的异常钙释放、缩短的心房不应期和心房扩张与观察到的心房心律失常、二联律和心房心动过速一致，而 MyBP-HL 阳性细胞与心室传导系统的接近为主要在心房表达的基因如何导致心室心律失常和心室功能障碍提供了深入了解。
