Developmentally regulated switching of titin size alters myofibrillar stiffness in the perinatal heart
Developmentally regulated switching of titin size alters myofibrillar stiffness in the perinatal heart
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DOI：
10.1161/01.res.0000124301.48193.e1
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发表时间：
2004-04-16
影响因子：
20.1
通讯作者：
Linke, WA
中科院分区：
文献类型：
--
作者：
Opitz, CA;Leake, MC;Linke, WA
出生前，心脏的顺应性主要受到心外约束的限制。出生时减少这种限制要求心肌顺应性主要由心脏自身成分决定。由于肌联蛋白是心室被动张力（PT）的主要贡献者，我们研究了心脏肌联蛋白异构体在围产期大鼠心脏发育过程中的表达和机制。凝胶电泳和免疫印迹显示，一个单一的，3.7-MDa，N2 BA亚型目前出生前6天和一个额外的，以前也是未知的，N2 BA亚型的3.5至3.6 MDa在近足月胎儿中表达。这些大的亚型在出生后迅速消失，并被一个小的N2 B亚型（3.0 MDa）取代，主要在1周龄和成年大鼠中。此外，新生猪心脏显示出与成年猪心肌中存在的那些不同的大N2 BA-肌联蛋白亚型。通过定量逆转录聚合酶链反应，发育中表达的肌联蛋白-mRNA的物种检测在大鼠心脏。胎鼠心肌细胞中基于Titin的PT比成年大鼠心肌细胞低得多（约15倍），用蠕虫样链Titin弹性模型可以很容易地预测测得的PT水平。免疫荧光显微镜显示，胎儿/新生儿肌联蛋白异构体在离体大鼠心肌原纤维的差异剪接分子弹簧区域的可扩展性。而肌联蛋白亚型移位700 kDa确保出生后心脏肌原纤维的高被动刚度，特定的胎儿/新生儿心脏肌联蛋白亚型的表达也可能具有重要的功能，收缩性能，肌原纤维组装或营业额，和围产期心脏发育期间的心肌信号。
Before birth, the compliance of the heart is limited predominantly by extracardiac constraint. Reduction of this constraint at birth requires that myocardial compliance be determined mainly by the heart's own constituents. Because titin is a principal contributor to ventricular passive tension ( PT), we studied the expression and mechanics of cardiac-titin isoforms during perinatal rat heart development. Gel electrophoresis and immunoblotting revealed a single, 3.7-MDa, N2BA isoform present 6 days before birth and an additional, also previously unknown, N2BA isoform of 3.5 to 3.6 MDa expressed in the near-term fetus. These large isoforms rapidly disappear after birth and are replaced by a small N2B isoform (3.0 MDa) predominating in 1-week-old and adult rats. In addition, neonatal pig hearts showed large N2BA-titin isoforms distinct from those present in the adult porcine myocardium. By quantitative reverse transcriptase polymerase chain reaction, developmentally expressed titin-mRNA species were detected in rat heart. Titin-based PT was much lower (approximate to15 times) in fetal than adult rat cardiomyocytes, and measured PT levels were readily predictable with a model of worm-like chain titin elasticity. Immunofluorescence microscopy showed the extensibility of the differentially spliced molecular spring regions of fetal/neonatal titin isoforms in isolated rat cardiomyofibrils. Whereas the titin-isoform shift by 700 kDa ensures high passive stiffness of the postnatal cardiac myofibrils,the expression of specific fetal/neonatal cardiac-titin isoforms may also have important functions for contractile properties, myofibril assembly or turnover, and myocardial signaling during perinatal heart development.