Starich T A, Herman R K, Shaw J E
Department of Genetics and Cell Biology, University of Minnesota, St. Paul 55108.
Genetics. 1993 Mar;133(3):527-41. doi: 10.1093/genetics/133.3.527.
Mutations in the Caenorhabditis elegans gene unc-7 confer an uncoordinated phenotype. Wild-type animals trace smooth, sinuous waves as they move; unc-7 mutants make irregular bends or kinks along their bodies, particularly when they move forward. The unc-7 locus has also been implicated in the nematode's response to volatile anesthetics. We have cloned unc-7 by transposon tagging: an unc-7 mutation was correlated with the insertion of the transposon Tc1, and reversion of the mutant phenotype was correlated with loss of the Tc1 element. We have physically mapped the region flanking the sites of Tc1 insertion and identified DNA rearrangements corresponding to eight additional unc-7 alleles. Northern analysis indicates that a 2.7-kb unc-7 message is present in all developmental stages but is most abundant in L1-L3 larvae. The 5' end of the message contains a trans-spliced leader SL1. An 18-kb intron is located upstream of the predicted translational start site of the gene, and DNA breakpoints of four gamma-ray-induced alleles were located within this intron. We determined the sequence of a cDNA corresponding to the unc-7 message. The message may encode a 60-kd protein whose amino acid sequence is unrelated to any other available protein sequence; a transmembrane location for the unc-7 protein is predicted. We predict from our analysis of unc-7 genetic mosaics that the unc-7 gene product is not required in muscle cells for wild-type coordination but is probably required in motor neurons (although a hypodermal role has not been excluded). We speculate that unc-7 may be involved in the function of neuronal ion channels.
秀丽隐杆线虫unc-7基因的突变会导致不协调的表型。野生型动物移动时会留下平滑、蜿蜒的轨迹；unc-7突变体在身体上会出现不规则的弯曲或扭结，尤其是在向前移动时。unc-7基因座也与线虫对挥发性麻醉剂的反应有关。我们通过转座子标签克隆了unc-7：unc-7突变与转座子Tc1的插入相关，而突变体表型的回复与Tc1元件的缺失相关。我们对Tc1插入位点两侧的区域进行了物理定位，并鉴定出与另外八个unc-7等位基因相对应的DNA重排。Northern分析表明，2.7 kb的unc-7信使RNA在所有发育阶段均有表达，但在L1-L3幼虫中最为丰富。该信使RNA的5'端含有一个反式剪接前导序列SL1。一个18 kb的内含子位于该基因预测的翻译起始位点上游，四个γ射线诱导等位基因的DNA断点位于此内含子内。我们确定了与unc-7信使RNA对应的cDNA序列。该信使RNA可能编码一种60 kd的蛋白质，其氨基酸序列与任何其他已知蛋白质序列均无关联；预测unc-7蛋白具有跨膜定位。通过对unc-7基因嵌合体的分析，我们推测野生型协调功能在肌肉细胞中不需要unc-7基因产物，但可能在运动神经元中需要（尽管尚未排除其在皮下组织中的作用）。我们推测unc-7可能参与神经元离子通道的功能。
