Understanding the molecular mechanism of cardiomyocyte dedifferentiation and proliferation during regeneration

1心脏病是死亡的主要原因，也是社会的重大健康负担，特别是心肌梗死。 2梗塞是造成世界范围内大量过早死亡的原因。在心脏缺血事件之后， 3.受损细胞通过坏死和凋亡死亡，并被瘢痕组织取代。纤维化疤痕组织的存在 4降低了心脏功能，并且随着时间的推移，梗塞的心脏发生衰竭。最近的研究表明， 5有限数量的备用心肌细胞可以去分化和增殖，以响应损伤，但这一点是不可能的。 6过程未能充分替换丢失的细胞。然而，这些研究提供了新的方法来刺激心脏， 7修理。一个明显的障碍是了解成熟的哺乳动物心肌细胞是如何被限制从 8成人心脏的增殖。尽管哺乳动物的心脏在修复和再生方面表现出有限的能力， 成年斑马鱼心脏对各种损伤模型具有强大的再生反应。成人 10.斑马鱼心脏可有效复制心肌细胞，并可刺激内皮细胞和冠状血管 11再生，使得损伤或丢失的组织在几周内完全被替换。该提案的主要目标是 12是了解斑马鱼的心脏，特别是心肌细胞是如何响应心室收缩而激活的。 13例损伤去分化和增殖。这些研究的结果将提供重要的因素， 14用于驱动损伤后心肌细胞细胞周期的完成。在初步研究中，我们进行了转录组 在心室切除的心脏上进行RNA测序，并鉴定了许多高表达的基因， 16受伤后我们的研究表明，这些基因之一，叉头转录因子，foxm 1， 17在损伤边界区域内的心肌细胞中上调。foxm 1突变斑马鱼的研究 18例显示心肌细胞周期减少，心室切除后未能解决瘢痕组织。 19转录组分析foxm 1突变心脏显示相关细胞周期基因表达显著降低 20在G2/M转换中的表达表明Foxm 1可能是心肌细胞胞质分裂的关键驱动因素。另外我们 21人已经鉴定出参与心肌细胞分化的候选foxm 1靶基因， 22有丝分裂。因此，我们建议表征心肌细胞去分化的分子控制， 23增殖通过广泛研究foxm 1和下游靶基因。这些研究的结果 24将确定新的分子途径和因子，有可能刺激修复和再生 心肌梗死后25例，以解决社会健康负担。

1 Heart disease is the leading cause of death and a significant health burden to society, in particular myocardial 2 infarctions are responsible for a large number of premature deaths world-wide. After a cardiac ischemic event, 3 damaged cells die via necrosis and apoptosis and is replaced by scar tissue. The presence of fibrotic scar tissue 4 diminishes cardiac function and overtime infarcted hearts undergo failure. Recent studies have shown that a 5 limited number of spared cardiomyocytes can dedifferentiate and proliferate in response to injury, but this 6 process fails to sufficiently replace lost cells. However, these studies offer new approaches to stimulate cardiac 7 repair. One clear obstacle is to understand the how mature mammalian cardiomyocytes are restricted from 8 proliferation in the adult hearts. Although the mammalian heart shows limited capacity in repair and regeneration, 9 the adult zebrafish heart is endowed with a robust regenerative response to a variety of injury models. The adult 10 zebrafish heart can efficiently replicate cardiomyocytes, and can stimulate endocardium and coronary vessel 11 regeneration such that damage or lost tissue is completely replaced within weeks. The major goal of this proposal 12 is to understand how the zebrafish heart, specifically cardiomyocytes are activated in response to ventricular 13 injury to dedifferentiate and proliferate. Findings from these studies will provide important factors that are critical 14 for driving completion of cardiomyocyte cell cycle after injury. In preliminary studies, we performed transcriptome 15 profiling (RNA-seq) on ventricular resected hearts and identified a number of genes that are highly expressed 16 following injury. Our studies reveal that one of these genes, the forkhead transcription factor, foxm1 is 17 upregulated in cardiomyocytes that are within the injury border zone. Studies with foxm1 mutant zebrafish 18 showed cardiomyocyte cell cycling was diminished and failure to resolve scar tissue upon ventricular resection. 19 Transcriptome profiling foxm1 mutant hearts show a marked decrease in expression of cell cycle genes involved 20 in G2/M transition suggesting that Foxm1 may be a critical driver of cardiomyocyte cytokinesis. In addition, we 21 have identified candidate foxm1 target genes implicated to be involved in cardiomyocyte differentiation and 22 mitosis. We therefore propose to characterize the molecular control of cardiomyocyte dedifferentiation and 23 proliferation through extensive study of foxm1 and downstream target genes. The findings from these studies 24 will identify new molecular pathways and factors to that have the potential to stimulate repair and regeneration 25 after myocardial infarction to address a societal health burden.