Chen L, Krause M, Sepanski M, Fire A
Carnegie Institute of Washington, Department of Embryology, Baltimore, MD 21210.
Development. 1994 Jun;120(6):1631-41. doi: 10.1242/dev.120.6.1631.
A family of muscle-specific helix-loop-helix transcription factors (myoD, myogenin, myf-5 and MRF4) has been implicated in the control of vertebrate skeletal myogenesis. Searches for homologues of this family in Caenorhabditis elegans identified a single family member, hlh-1, which is expressed in striated muscles and their clonal precursors. We have isolated a null allele of hlh-1 following chemical mutagenesis. Animals homozygous for the null mutation produce contractile body-wall muscles, although muscle contractions are weak and coordination is defective. In addition to the evident muscle defects, mutant animals fail to complete embryonic elongation and die as larvae or young adults. Ultrastructural analysis of the mutant muscle reveals an apparently normal local lattice of thick and thin filaments, with more global defects in sarcomere organization and muscle cell placement. Mosaic studies using the point mutation and an extrachromosomal transgene indicate that the requirement for hlh-1 is fully zygotic, with no maternal hlh-1 requirement for either muscle development or viability.
一个肌肉特异性螺旋-环-螺旋转录因子家族（肌分化因子、肌细胞生成素、肌因子-5和MRF4）参与了脊椎动物骨骼肌生成的调控。在秀丽隐杆线虫中寻找该家族的同源物时，鉴定出了一个单一的家族成员hlh-1，它在横纹肌及其克隆前体细胞中表达。我们在化学诱变后分离出了hlh-1的一个无效等位基因。纯合无效突变的动物会产生收缩性体壁肌肉，尽管肌肉收缩较弱且协调性存在缺陷。除了明显的肌肉缺陷外，突变动物无法完成胚胎伸长，并在幼虫或年轻成虫阶段死亡。对突变肌肉的超微结构分析显示，粗细肌丝的局部晶格明显正常，但肌节组织和肌肉细胞位置存在更广泛的缺陷。使用点突变和染色体外转基因进行的镶嵌研究表明，对hlh-1的需求完全是合子性的，肌肉发育或生存能力对母本hlh-1没有需求。
