microRNA-26b在心肌细胞分化中对GATA4和KCNJ2的同步调节机制

The defects of heart development often associated with arrhythmias, but the mechanism underlying remains unclear. It has been shown that GATA4， a cardiac transcription factor involved in the cardiomyocyte lineage-specific differentiation , is one of the direct regulatory target of miR-26b. On the other hand, KCNJ2， which encodes inward rectifier potassium channel， is one of the characteristic genes responsible for maintaining electrical activity of cardiomyocytes in normal expression. We found that GATA4 mutations associated with abnormal heart development and dysfunction, and miR-26b was significantly down-regulated in patients with atrial fibrillation and cardiac structural abnormalities. These evidence with our bioinformatic prediction strongly suggests that miR-26b may potentially regulate pathogenic gene KCNJ2 in atrial fibrillation. Therefore, we hypothesized: miR-26b may not only mediate the expression of GATA4 to promote cardiomyocyte differentiation, but also directly and / or indirectly control KCNJ2 expression in synchronization, thus ensuring the differentiated cardiomyocyte with the characteristic ECG basis. To this end, we will perform a series of experiments in both ES cell and cardiac stem cell with differentiation, combined with bioinformatics, molecular, cellular, biochemical, and electrophysiological technology to explore the scientific issues in this topic in order to providing some reference for understanding the mechanisms of relationship between heart developmental defects and arrhythmias.

心脏发育缺陷常伴有心律失常，但其发生机制仍不清楚。已知心脏转录因子GATA4参与心肌细胞系谱的特异分化，并受miR-26b 的调控。而编码内向整流钾离子通道的KCNJ2是心肌细胞特征性基因之一，其正常表达是维系成熟心肌细胞电活动的重要分子基础。我们研究发现：GATA4的突变与心脏发育与功能异常关联；而miR-26b在心脏结构异常伴有心房颤动的病人中呈现低表达，并可潜在地调节心房颤动致病基因KCNJ2。因此，我们推测：miR-26b可介导GATA4的表达促进心肌细胞分化，同时也直接和/或间接调控KCNJ2的同步表达，从而保证分化的心肌细胞具有特征性的心电基础。为此，我们将利用胚胎干细胞和心脏干细胞进行分化实验，并结合生物信息、分子、细胞、生化和电生理技术对本课题的科学问题进行探讨。为理解心律失常与心脏发育缺陷关系的机制提供实验依据。

干细胞向心肌细胞分化是一个复杂动态的过程。相关基因随着分化被激活和关闭受到严格的调控，并在不同分化阶段呈现有序的表达规律。表观遗传在心肌分化中起着重要的调节作用。因此，了解表观遗传如微小RNA、组蛋白乙酰化等在此过程中的调节机制将有助于了解心脏正常发育以及心脏疾病的机制。本课题主要聚焦心肌细胞分化过程中，miR-26b对心脏转录因子GATA4以及Kcnj2和PLCβ1等的调节以及miR-218在心脏肥大中的作用机制： miR-26b通过抑制Wnt5a 和Gsk3β的表达，促进心肌相关基因的表达，从而促进P19细胞向心肌细胞的分化和增值。miR-218在异丙肾上腺素诱导的心肌细胞肥大过程中起对抗心肌肥厚的作用，其特异地负性调控心脏及血管平滑肌发育过程中关键的转录调节因子REST的表达，在主动脉狭窄心肌肥厚模型中过表达miR-218也能显著抑制REST的蛋白表达水平。.此外，本课题还发现两个与先天性心脏病有关的转录因子GATA4和PITX2新的功能丧失性突变。上述这些成果为研究心脏病的发病机制提供了线索。课题发表了相关SCI论文7篇，申请了2项专利，培养硕士/博士研究生12名。