Johnstone D B, Wei A, Butler A, Salkoff L, Thomas J H
Department of Genetics, University of Washington, Seattle 98195, USA.
Neuron. 1997 Jul;19(1):151-64. doi: 10.1016/s0896-6273(00)80355-4.
Mutations in the C. elegans egl-36 gene result in defective excitation of egg-laying and enteric muscles. Dominant gain-of-function alleles inhibit enteric and egg-laying muscle contraction, whereas a putative null mutation has no observed phenotype. egl-36 encodes a Shaw-type (Kv3) voltage-dependent potassium channel subunit. In Xenopus oocytes, wild-type egl-36 expresses noninactivating channels with slow activation kinetics. One gain-of-function mutation causes a single amino acid substitution in S6, and the other causes a substitution in the cytoplasmic amino terminal domain. Both mutant alleles produce channels dramatically shifted in their midpoints of activation toward hyperpolarized voltages. An egl-36::gfp fusion is expressed in egg-laying muscles and in a pair of enteric muscle motor neurons. The mutant egl-36 phenotypes can thus be explained by expression in these cells of potassium channels that are inappropriately opened at hyperpolarized potentials, causing decreased excitability due to increased potassium conductance.
秀丽隐杆线虫egl-36基因的突变会导致产卵和肠道肌肉的兴奋缺陷。显性功能获得性等位基因会抑制肠道和产卵肌肉的收缩，而一个假定的无效突变未观察到表型。egl-36编码一个Shaw型（Kv3）电压依赖性钾通道亚基。在非洲爪蟾卵母细胞中，野生型egl-36表达具有缓慢激活动力学的非失活通道。一个功能获得性突变在S6中导致单个氨基酸替换，另一个在细胞质氨基末端结构域导致替换。两个突变等位基因产生的通道在其激活中点向超极化电压方向发生显著偏移。一个egl-36::gfp融合蛋白在产卵肌肉和一对肠道肌肉运动神经元中表达。因此，egl-36突变表型可以通过在这些细胞中表达在超极化电位下不适当开放的钾通道来解释，这会由于钾电导增加而导致兴奋性降低。
