Studies of muscle proteins in embryonic myocardial cells of cardiac lethal mutant mexican axolotls (Ambystoma mexicanum) by use of heavy meromyosin binding and sodium dodecyl sulfate polyacrylamide gel electrophoresis.
Studies of muscle proteins in embryonic myocardial cells of cardiac lethal mutant mexican axolotls (Ambystoma mexicanum) by use of heavy meromyosin binding and sodium dodecyl sulfate polyacrylamide gel electrophoresis.
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DOI：
10.1083/jcb.68.2.375
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发表时间：
1976-02
期刊：
影响因子：
--
通讯作者：
Iyengar MR
中科院分区：
文献类型：
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作者：
Lemanski LF;Mooseker MS;Peachey LD;Iyengar MR
在墨西哥蝾螈Ambystoma mexicanum隐性突变基因c中，通过来自周围组织的异常诱导过程，导致胚胎心脏功能的缺失。突变心脏细胞缺乏收缩，显然是由于它们不能形成正常组织的肌原纤维，即使存在一些肌动蛋白样（60-A）和肌球蛋白样（150-A）细丝。通常可见无定形的“蛋白质”集合体。在目前的研究中，重酶解肌球蛋白（HMM）处理突变心脏组织大大增加了细丝的数量，并以通常的方式装饰它们，证实它们是肌动蛋白。无定形集合随着HMM的加入而消失。此外，通过十二烷基硫酸钠（SDS）凝胶电泳分析正常和突变胚胎心脏和其他组织的组成蛋白。这些实验与形态学和HMM结合研究完全一致。凝胶显示正常和突变心脏的42，000-道尔顿条带，支持正常肌动蛋白的存在。在早期发育阶段（哈里森34期），正常和突变兄弟姐妹的心脏组织具有不可区分的带型，但随着发育的增加，出现了一些差异。肌球蛋白重链（200，000道尔顿）在发育过程中在正常心脏中大量增加，但在突变体中很少。即便如此，突变心脏中的20万道尔顿蛋白质的数量也明显多于任何一种被研究的非肌肉组织（即肠道、肝脏、大脑）。与正常心脏不同，突变心脏缺乏一个显著的34，000-道尔顿条带，这表明如果突变体含有肌肉原肌球蛋白，它的含量会急剧减少。此外，当血小板从正常心脏中几乎消失时，突变心脏保留了大量的卵黄蛋白。正常和突变同胞骨骼肌的形态和电泳模式是相同的，证实基因c只影响心肌分化，而不影响骨骼肌。这项研究的结果表明，心脏致死突变蝾螈胚胎的心前中胚层启动，但随后未能完成其分化为功能性肌肉组织。看来，这个单一的基因突变，通过异常的诱导过程，影响积累和组织的几种不同的肌肉蛋白，包括肌动蛋白，肌球蛋白，原肌球蛋白。
In the Mexican axolotl Ambystoma mexicanum recessive mutant gene c, by way of abnormal inductive processes from surrounding tissues, results in an absence of embryonic heart function. The lack of contractions in mutant heart cells apparently results from their inability to form normally organized myofibrils, even though a few actin-like (60-A) and myosin-like (150-A) filaments are present. Amorphous "proteinaceous" collections are often visible. In the present study, heavy meromyosin (HMM) treatment of mutant heart tissue greatly increases the number of thin filaments and decorates them in the usual fashion, confirming that they are actin. The amorphous collections disappear with the addition of HMM. In addition, an analysis of the constituent proteins of normal and mutant embryonic hearts and other tissues is made by sodium dodecyl sulfate (SDS) gel electrophoresis. These experiments are in full agreement with the morphological and HMM binding studies. The gels show distinct 42,000-dalton bands for both normal and mutant hearts, supporting the presence of normal actin. During early developmental stages (Harrison's stage 34) the cardiac tissues in normal and mutant siblings have indistinguishable banding patterns, but with increasing development several differences appear. Myosin heavy chain (200,000 daltons) increases substantially in normal hearts during development but very little in mutants. Even so the quantity of 200,000-dalton protein in mutant hearts is significantly more than in any of the nonmuscle tissues studied (i.e. gut, liver, brain). Unlike normal hearts, the mutant hearts lack a prominent 34,000-dalton band, indicating that if mutants contain muscle tropomyosin at all, it is present in drastically reduced amounts. Also, mutant hearts retain large amounts of yolk proteins at stages when the platelets have virtually disappeared from normal hearts. The morphologies and electrophoresis patterns of skeletal muscle from normal and mutant siblings are identical, confirming that gene c affects only heart muscle differentiation and not skeletal muscle. The results of the study suggest that the precardiac mesoderm in cardiac lethal mutant axolotl embryos initiates but then fails to complete its differentiation into functional muscle tissue. It appears that this single gene mutation, by way of abnormal inductive processes, affects the accumulation and organization of several different muscle proteins, including actin, myosin, and tropomyosin.