Molecular Mechanisms of Muscle Cell Differentiation in Embryos Ascidian

海鞘胚胎的肌细胞分化的分子机制进行了研究，相对于一个极端的潜力自主分化的cells.First，我们已经分离出肌球蛋白重链和museletype肌动蛋白的cDNA克隆。这些肌肉特异性基因在原肠胚形成时表达，并且仅限于分化中的小肠细胞。海鞘胚胎合成几种不同的肌动蛋白mRNA。其中一个克隆HrcMA 4包含1137 bp的开放阅读框和100 bp的非编码区，随后是poly（A）尾。然后，我们分离了含有HrMA4基因的基因组片段。该基因的表征表明，HrMA4是由两个内含子中断。有几个潜在的调控元件的基因的准确表达。此外，很明显，HrMA4和其他几个肌肉肌动蛋白基因形成一个cluster.Second，我们试图分离基因的肌源性因子，如MyoD1和myogenic。最后，我们通过制备几种单克隆抗体，对被认为含有成肌因子的肌浆大分子进行了分析。其中一种抗体注射到受精卵后会阻止肌肉发育。然而，抗原性多肽的表征表明，它与细胞骨架蛋白有关。

Molecular mechanisms of muscle cell differentiation of ascidian embryos have been investigated with respect to an extreme potential of autonomous differentiation of the cells.First, we have isolated CDNA clones for myosin-heavy chain and museletype actins. Expression of these muscle-specific genes beans around the time of gastrulation, and is restricted to differentiating sele cells. Ascidian embryos synthesize several different actin mRNAs. One of the clones, HrcMA4 contains an open reading frame of 1137 bp and a 100 bp noncoding region followed by a poly(A)tail. Then, we have isolated genomic fragments that contain HrMA4 gene. Characterization of the gene shows that HrMA4 is interrupted by two introns. There are several potential regulatory elements for accurate expression of the gene. In addition, it becomes clear that HrMA4 and several other muscle-actin genes form a cluster.Second, we have tried to isolate genes for myogenic factors such as MyoDl and myogenic. S6 far, we have obtained by PCR method a candidate DNA-fragment for the genes.Finally, we have analyzed macromolecules of the myoplasm, which is thought to contain the myogenic factors, by producing several monoclonal antibodies. One of the antibodies blocks muscle development when it is injected into fertilized eggs. Characterization of the antigenic polypeptide, however, has shown that it is related to cytoskeletal proteins.