Hutter Harald, Wacker Irene, Schmid Christina, Hedgecock Edward M
Max-Planck-Institut für medizinische Forschung, Jahnstr. 29, 69120 Heidelberg, Germany.
Dev Biol. 2005 Aug 1;284(1):260-72. doi: 10.1016/j.ydbio.2005.05.025.
The ventral cord in C. elegans is the major longitudinal axon tract containing essential components of the motor circuit. In genetic screens using transgenic animals expressing neuron specific GFP reporters, we identified twelve genes required for the correct outgrowth of interneuron axons of the motor circuit. In mutant animals, axons fail to navigate correctly towards the ventral cord or fail to fasciculate correctly within the ventral cord. Several of those mutants define previously uncharacterized genes. Two of the genes, ast-4 and ast-7, are involved in the generation of left-right asymmetry of the two ventral cord axon tracts. Three other genes specifically affect pioneer-follower relationships between early and late outgrowing axons, controlling either differentiation of a pioneer neuron (lin-11) or the ability of axons to follow a pioneer (ast-2, unc-130). Navigation of the ventral cord pioneer neuron AVG itself is defective in ast-4, ast-6 and unc-130 mutants. Correlation of these defects with navigation defects in different classes of follower axons revealed a true pioneer role for AVG in the guidance of interneurons in the ventral cord. Taken together, these genes provide a basis to address different aspects of axon navigation within the ventral cord of C. elegans.
秀丽隐杆线虫的腹神经索是主要的纵向轴突束，包含运动回路的基本组成部分。在使用表达神经元特异性绿色荧光蛋白报告基因的转基因动物进行的遗传筛选中，我们鉴定出12个基因，它们是运动回路中间神经元轴突正确生长所必需的。在突变动物中，轴突无法正确地向腹神经索导航，或者在腹神经索内无法正确地成束。其中一些突变体定义了以前未被表征的基因。其中两个基因，ast-4和ast-7，参与了两条腹神经索轴突束左右不对称性的产生。另外三个基因特别影响早期和晚期生长轴突之间的先驱-跟随者关系，控制先驱神经元（lin-11）的分化或轴突跟随先驱的能力（ast-2，unc-130）。腹神经索先驱神经元AVG自身的导航在ast-4、ast-6和unc-130突变体中存在缺陷。这些缺陷与不同类型跟随轴突的导航缺陷之间的相关性揭示了AVG在腹神经索中间神经元导向中真正的先驱作用。综上所述，这些基因为研究秀丽隐杆线虫腹神经索内轴突导航的不同方面提供了基础。
