Chun M, Falkenthal S
Department of Molecular Genetics, Ohio State University, Columbus 43210.
J Cell Biol. 1988 Dec;107(6 Pt 2):2613-21. doi: 10.1083/jcb.107.6.2613.
Using a combination of molecular and genetic techniques we demonstrate that Ifm(2)2 is an allele of the single-copy sarcomeric myosin heavy chain gene. Flies homozygous for this allele accumulate wild-type levels of mRNA and protein in tubular muscle of adults, but fail to accumulate detectable amounts of myosin heavy chain mRNA or protein in the indirect flight muscle. We propose that the mutation interferes with either transcription of the gene or splicing of the primary transcript in the indirect flight muscle and not in other muscle tissues. Biochemical and electron microscopic analysis of flies homozygous for this mutation has revealed that thick filament assembly is abolished in the indirect flight muscle resulting in the instability of wild-type thick filament proteins. In contrast, thin filament and Z disc assembly are marginally affected. We discuss a working hypothesis for sarcomere assembly and define and experimental approach to test the predictions of this proposed pathway for sarcomere assembly.
通过结合分子和遗传技术，我们证明Ifm(2)2是单拷贝肌节肌球蛋白重链基因的一个等位基因。该等位基因的纯合果蝇在成虫的管状肌肉中积累野生型水平的mRNA和蛋白质，但在间接飞行肌中未能积累可检测量的肌球蛋白重链mRNA或蛋白质。我们认为，该突变干扰了间接飞行肌而非其他肌肉组织中该基因的转录或初级转录本的剪接。对该突变纯合果蝇的生化和电子显微镜分析表明，间接飞行肌中的粗肌丝组装被消除，导致野生型粗肌丝蛋白不稳定。相比之下，细肌丝和Z盘组装受到的影响较小。我们讨论了肌节组装的一个工作假设，并定义了一种实验方法来检验这一提出的肌节组装途径的预测。
