Cardiac morphogenesis and myofibrillogenesis

1.发育过程中肌原纤维蛋白异构体变化的机制用VSV或mT抗原标记的两种不同的肌球蛋白碱性轻链（LC）异构体cDNA的各种组合在培养的大鼠和鸡心室肌细胞中共表达。使用针对标签的抗体检测表达的同工蛋白，并通过共聚焦显微镜分析其分选模式。LC异构体的分选特异性肌节被证明增加以下发育表达序列的顺序：非肌肉，慢骨骼肌，心室，和快骨骼肌型。这表明，在肌原纤维形成过程中，对肌原纤维具有逐渐更高的结合亲和力的同种型有效地取代了先前的蛋白质，确保了同种型的快速交换，而没有蛋白质合成的显著增加。嵌合cDNA的表达揭示了每个同种蛋白N-末端叶中的第二个EF-手负责同种型- ...更多信息 特定的排序模式。虽然该部分不包括在与肌球蛋白重链的关键接触中，但该结构域中的氨基酸差异可能影响相邻结构域的相对布置，从而影响关键接触的精确关联。心肌和骨骼肌肌钙蛋白I（CTnI和FTnI）及其突变体（嵌合型和截短型TnI）在培养的肌细胞中强制表达，以研究TnI异构体掺入肌原纤维（Mfs）的机制。由于CTnI没有被纳入乳腺Mfs，CTnI的分选机制似乎存在于乳腺Mfs中。嵌合型和截短型TnI的分析表明，TnI由两个功能不同的结构域组成：C端结构域与Mfs结合，N端结构域调节与心脏和乳腺Mfs的结合亲和力和特异性.心脏的形态发生和畸形发生用扫描电镜观察了胚胎心脏壁的形态。证明了构成胚胎心脏的四种异型细胞的不同表面特征。心外膜细胞从静脉窦的间皮层迁移，环绕心室壁，然后向头/尾方向延伸以使整个心脏表面脱离鞘管。孕鼠第8天给予维甲酸20 mg/kg体重，心脏畸形发生率极高。观察到的异常是：TGA、DORV、VSD、A环和L环。少

1. Mechanisms of myofibrillar protein isoform changes during developmentVarious combinations of two different myosin alkali light chain (LC) isoform cDNAs tagged with either VSV or mT antigen were co-exapressed in cultured cardiomyocytes from rat and chicken ventricles. Expressed isoproteins were detected using antibodies against the tags and their sorting patterns were analyzed by conforcal microscopy. The sorting specificity of LC isoforms to sarcomeres was shown to increase in the order of following developmental expression sequence : nonmuscle, slow skeletal muscle, ventricular, and fast skeletal muscle type. This suggests that during myofibrillogenesis isoforms with progressively higher binding affinities to myofibrils efficiently replace previous proteins, ensuring rapid exchange of isoforms without an extraordinary increase in protein synthesis. Expression of chimeric cDNAs revealed that the second EF-hand in the N-terminal lobe of each isoprotein is responsible for the isoform- … More specific sorting pattern. Although this part is not included in the key contact (s) with the myosin heavy chain, amino acid differences in this domain might affect the relative disposition of neighboring domains, thereby influencing the precise association of the key contact (s).2. Behavior of cardiac and skeletal muscle type isoproteins during myofibrillogenesisCardiac and skeletal (breast) muscle troponin Is (CTnI and FTnI,respectively) and their mutants (chimeric and truncated TnIs) were force expressed in cultured muscle cells to examine incorporation mechanism of TnI isoforms into myofibrils (Mfs). Since CTnI was not incorporated into breast Mfs, sorting mechanism of CTnI appeared to exist in breast MFs. Analysis of chimeric and truncated TnIs showed that TnIs were composed of two functionally distinct domains : C-terminal domain which binds to Mfs and N-terminal domain regulating the strength of binding affinity and specificity to cardiac and breast MFs.3. Morphogenesis and teratogenesis of the heartThe cardiac wall in embryos was investigated with the scanning electron microscope. The different surface characteristics of the four heterotypic cells that constitute the embryonic heart were demonstrated. The epicardial cells migrate from the mesothelium of the sinus venousus, encircled the ventricular wall, then extended cranically/caudally to unsheathe the entire heart usrface. Incidence of cardiac malformation was very high if retionic acid was administered into pregnant mice on 8ed day at the dose of 20 mg/kg body weight. Abnormalities observed are : TGA,DORV,VSD,A-loop and L-loop. Less