Cyclin‐dependent kinase 9 forms a complex with GATA4 and is involved in the differentiation of mouse ES cells into cardiomyocytes

The treatment of ES cells with trichostatin A (TSA), an HDAC inhibitor, induces the acetylation of GATA4 as well as histones, and facilitates their differentiation into cardiomyocytes. Recently, we demonstrated that cyclin‐dependent kinase 9 (Cdk9), a core component of positive elongation factor‐b, is a novel GATA4‐binding partner. The present study examined whether Cdk9 forms a complex with GATA4 in mouse ES cells and is involved in their differentiation into cardiomyocytes. Mouse ES cells and Nkx2.5/GFP ES cells, in which green fluorescent protein (GFP) is expressed under the control of the cardiac‐specific Nkx2.5 promoter, were induced to differentiate on feeder‐free gelatin‐coated plates. Immunoprecipitation/Western blotting in nuclear extracts from mouse ES cells demonstrated that Cdk9 as well as cyclin T1 interact with GATA4 during myocardial differentiation. TSA treatment increased Nkx2.5/GFP‐positive cells and endogenous mRNA levels of Nkx2.5 and atrial natriuretic factor. To determine the role of Cdk9 in myocardial cell differentiation, we examined the effects of a dominant‐negative form of Cdk9 (DN‐Cdk9), which loses its kinase activity, and a Cdk9 kinase inhibitor, 5,6‐dichloro‐1‐β‐ribofuranosyl‐benzimidazole (DRB) on TSA‐induced myocardial cell differentiation. The introduction of the DN‐Cdk9 inhibited TSA‐induced increase in GFP expression in Nkx2.5/GFP ES cells. The administration of DRB into ES cells significantly inhibited TSA‐induced increase of endogenous Nkx2.5 mRNA levels in ES cells as well as GFP expression in Nkx2.5/GFP ES cells. These findings demonstrate that Cdk9 is involved in the differentiation of mouse ES cells into cardiomyocytes by interacting with GATA4. J. Cell. Physiol. 226: 248–254, 2010. © 2010 Wiley‐Liss, Inc.     

大鼠心肌发育相关基因在心肌梗死后的表达变化

探讨大鼠急性心肌梗死后与心肌发育相关基因的表达变化 .通过结扎大鼠冠状动脉左前降支建立急性心肌梗死模型 ,利用逆转录聚合酶链式反应 (RT PCR)和Northern印迹技术分别检测GATA4、Nkx2 5BMP2和Wnt11基因在心肌梗死后不同时间的表达变化趋势 .结果显示 ,在正常心肌中 ,与心肌发育相关的基因GATA4、Nkx2 5和BMP2有较强的表达 ,而Wnt11基础表达较低 .心肌梗死后 ,GATA4、Nkx2 5和BMP2表达下降 ,7d后有所恢复 ;Wnt11的表达在心肌梗死后呈上升趋势 ,至梗死 7d达到高峰 .结果提示 ,心肌发育相关基因的表达在心肌梗死后有明显改变 ,并发现启动心肌发育的关键信号分子———Wnt11基因表达上调 ,为心肌损伤后细胞分化机制的研究提供线索