Skeletal muscle-specific myosin binding protein-H is expressed in Purkinje fibers of the cardiac conduction system
Skeletal muscle-specific myosin binding protein-H is expressed in Purkinje fibers of the cardiac conduction system
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DOI：
10.1161/01.res.80.5.665
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发表时间：
1997-05-01
影响因子：
20.1
通讯作者：
Mikawa, T
中科院分区：
文献类型：
--
作者：
Alyonycheva, T;CohenGould, L;Mikawa, T
心脏收缩是通过心脏传导系统的专门组织的电兴奋传导来协调的。通过逆转录病毒单细胞标记和胚胎鸡心脏的谱系分析，我们最近证明了心肌细胞的一个亚群最终分化为外周传导系统的细胞（浦肯野纤维），并且这种情况总是发生在发育中的冠状动脉的血管周围区域。在传导系统中，在细胞转录调控中起作用的顺式调控元件已经与收缩性心肌细胞中的元件区别开来；例如，desmin基因的5'调控序列在骨骼肌和传导系统中起增强元件的作用，但在心肌中不起作用。我们假设浦肯野纤维分化涉及基因表达程序的转换，从心肌的特征到骨骼肌的一个典型。为了验证这一假设，我们检测了肌球蛋白结合蛋白h （MyBP-H）在鸡心脏浦肯野纤维中的表达。这种独特的肌球蛋白结合蛋白存在于骨骼细胞而不存在于心肌细胞。制备了针对MyBP-H的定点多克隆抗体（AB105）。心肌的免疫组织学分析将AB105抗原主要定位于浦肯野纤维内肌原纤维的A带。对成年鸡心室壁全提取物进行Western blot分析发现，AB105表位仅局限于一个约86 kD的蛋白，与骨骼肌中MyBP-H的大小相同。浦肯野纤维86-kD蛋白的生化特性及其mRNA的RNase保护分析表明，浦肯野纤维86-kD蛋白与骨骼肌MyBP-H难以区分。结果证明骨骼肌MyBP-H在分化为心脏浦肯野纤维的心肌细胞亚群中表达。
Heart contraction is coordinated by conduction of electrical excitation through specialized tissues of the cardiac conduction system. By retroviral single-cell tagging and lineage analyses in the embryonic chicken heart, we have recently demonstrated that a subset of cardiac muscle cells terminally differentiates as cells of the peripheral conduction system (Purkinje fibers) and that this occurs invariably in perivascular regions of developing coronary arteries. Cis regulatory elements that function in transcriptional regulation of cells in the conducting system have been distinguished from those in contractile cardiac muscle cells; eg, 5' regulatory sequences of the desmin gene act as enhancer elements in skeletal muscle and in the conduction system but not in cardiac muscle. We hypothesize that Purkinje fiber differentiation involves a switch of the gene expression program from that characteristic of cardiac muscle to one typical of skeletal muscle. To test this hypothesis, we examined the expression of myosin binding protein-H (MyBP-H) in Purkinje fibers of chicken hearts. This unique myosin binding protein is present in skeletal but not cardiac myocytes. A site-directed polyclonal antibody (AB105) was generated against MyBP-H. Immunohistological analysis of the myocardium mapped the AB105 antigen predominantly to A bands of myofibrils within Purkinje fibers. Western blot analysis of whole extracts from the ventricular wall of adult chicken hearts revealed that the AB105 epitope was restricted to a single protein of approximate to 86 kD, the same size as MyBP-H in skeletal muscle. Biochemical properties of the Purkinje fiber 86-kD protein and RNase protection analyses of its mRNA indicate that Purkinje fiber 86-kD protein is indistinguishable from skeletal muscle MyBP-H. The results provide evidence that skeletal muscle MyBP-H is expressed in a subset of cardiac muscle cells that differentiate into Purkinje fibers of the heart.