Genome-wide mRNA expression analyses revealed dysregulation of genes important for cardiomyocyte function in XMlc2-Cre;Dot1L mutants and controls

Epigenetic enzymes play critical roles in embryogenesis by defining higher-order chromatin structures required for the establishment of organ-specific transcriptional networks. In this study we investigated the role of the histone 3 lysine 79 methyltrasferase Dot1L in cardiomyocytes during development. Cardiomyocyte-specific ablation of Dot1L resulted in postnatal lethality with a cardiac phenotype of enlarged, rounded heart with increased ventricular wall thickness and areas of moderate trabeculation postnatally. To understand transciptomic alterations driving the observed phenotype, we conducted RNA-seq experiments in embryonic (E16.5) and neonatal (P1) cardiomyocytes from Dot1L conditional knock out and control mice. Overall, we identified downregulation of genes higly expressed and upregulaton of genes lowly expressed. Genes dowregulated in two critical stages of cardiac development analysed were indicative of defective cardiac patterning during embryogenesis, and defective cell cycle withdrawal in the neonatal period. RNA-seq analyses were performed on FACS purified cardiomyocytes from XMlc2-Cre;Dot1L mutant and controls at E16.5 and P1.表观遗传酶（Epigenetic enzymes）通过构建器官特异性转录调控网络所需的染色质高级结构，在胚胎发生过程中发挥关键作用。本研究探讨了组蛋白3赖氨酸79甲基转移酶（histone 3 lysine 79 methyltransferase，Dot1L）在发育中心肌细胞中的功能。研究发现，心肌细胞特异性敲除Dot1L会导致小鼠出现出生后致死性表型，其心脏特征为肿大变圆、心室壁厚度增加，且出生后可见中度肌小梁形成异常区域。为明确驱动该表型的转录组变化，我们对Dot1L条件性敲除（conditional knock out）及对照小鼠的胚胎期（E16.5）和新生期（P1）心肌细胞开展了RNA测序（RNA-seq）实验。整体分析结果显示，高表达基因出现下调，而低表达基因呈现上调。在两个关键心脏发育阶段中下调的基因，提示胚胎发生过程中存在心脏模式形成缺陷，以及新生期细胞周期退出异常。本研究的RNA测序分析样本均为经荧光激活细胞分选（FACS）纯化的心肌细胞，取自E16.5和P1阶段的XMlc2-Cre;Dot1L突变体及对照小鼠。