Department of Experimental Cardiology, Amsterdam Cardiovascular Sciences, Amsterdam UMC, location AMC, Amsterdam, The Netherlands.
Department of Physiology, Amsterdam Cardiovascular Sciences, Amsterdam UMC, location VUmc, Amsterdam, The Netherlands.
Sci Rep. 2020 May 6;10(1):7687. doi: 10.1038/s41598-020-64667-0.
RNA-binding proteins are key regulators of post-transcriptional processes such as alternative splicing and mRNA stabilization. Rbm24 acts as a regulator of alternative splicing in heart and skeletal muscle, and is essential for sarcomere assembly. Homozygous inactivation of Rbm24 in mice disrupts cardiac development and results in embryonic lethality around E12.5. In the present study, we generated somatic Rbm24 knockout (KO) mice and investigated the effects of reduced levels of Rbm24 in the adult heart. Due to the embryonic lethality of Rbm24 KO mice, we examined cardiac structure and function in adult Rbm24 heterozygotes (HETs). Rbm24 protein expression was 40% downregulated in HET hearts compared to WT hearts. Force measurements on isolated membrane-permeabilized myocytes showed increased sarcomere slack length and lower myofilament passive stiffness in adult Rbm24 HET compared to wildtype cardiomyocytes. As a result of the differences in sarcomere slack length, the relations between force development and sarcomere length differed between WT and Rbm24 HET hearts. No differences in sarcomere structure and titin isoform composition were observed. Likewise, in vivo cardiac function and myocardial structure was unaltered in Rbm24 HET mice compared to WT, at baseline and upon pressure overload after transverse aortic constriction. In conclusion, we generated a somatic Rbm24 KO model and recapitulated the previously reported embryonic phenotype. In adult Rbm24 HET cardiomyocytes we observed increased sarcomere slack length, but no difference in sarcomere structure and cardiac function.
RNA 结合蛋白是转录后过程（如选择性剪接和 mRNA 稳定）的关键调节剂。Rbm24 作为心脏和骨骼肌中选择性剪接的调节剂，对于肌节组装是必不可少的。Rbm24 基因在小鼠中的纯合失活会破坏心脏发育，并导致胚胎在 E12.5 左右致死。在本研究中，我们生成了体细胞 Rbm24 敲除（KO）小鼠，并研究了成年心脏中 Rbm24 水平降低的影响。由于 Rbm24 KO 小鼠的胚胎致死性，我们检查了成年 Rbm24 杂合子（HET）心脏的结构和功能。与 WT 心脏相比，HET 心脏中的 Rbm24 蛋白表达水平降低了 40%。对分离的膜通透肌原纤维的力测量显示，与野生型心肌细胞相比，成年 Rbm24 HET 中的肌节松弛长度增加，肌丝被动刚度降低。由于肌节松弛长度的差异，WT 和 Rbm24 HET 心脏中力发展与肌节长度之间的关系不同。未观察到肌节结构和肌联蛋白同工型组成的差异。同样，在 Rbm24 HET 小鼠与 WT 小鼠中，在基线时以及在经横主动脉缩窄后的压力超负荷时，心脏功能和心肌结构均未改变。总之，我们生成了一种体细胞 Rbm24 KO 模型，并重现了先前报道的胚胎表型。在成年 Rbm24 HET 心肌细胞中，我们观察到肌节松弛长度增加，但肌节结构和心脏功能没有差异。
