Chandrasekhar A, Moens C B, Warren J T, Kimmel C B, Kuwada J Y
Department of Biology, University of Michigan, Ann Arbor 48109-1048, USA.
Development. 1997 Jul;124(13):2633-44. doi: 10.1242/dev.124.13.2633.
The mechanisms underlying neuronal specification and axonogenesis in the vertebrate hindbrain are poorly understood. To address these questions, we have employed anatomical methods and mutational analysis to characterize the branchiomotor neurons in the zebrafish embryo. The zebrafish branchiomotor system is similar to those in the chick and mouse, except for the location of the nVII and nIX branchiomotor neurons. Developmental analyses of genes expressed by branchiomotor neurons suggest that the different location of the nVII neurons in the zebrafish may result from cell migration. To gain insight into the mechanisms underlying the organization and axonogenesis of these neurons, we examined the development of the branchiomotor pathways in neuronal mutants. The valentino b337 mutation blocks the formation of rhombomeres 5 and 6, and severely affects the development of the nVII and nIX motor nuclei. The cyclops b16 mutation deletes ventral midline cells in the neural tube, and leads to a severe disruption of most branchiomotor nuclei and axon pathways. These results demonstrate that rhombomere-specific cues and ventral midline cells play important roles in the development of the branchiomotor pathways.
脊椎动物后脑神经元特化和轴突发生的潜在机制目前了解甚少。为了解决这些问题，我们采用了解剖学方法和突变分析来表征斑马鱼胚胎中的鳃运动神经元。斑马鱼的鳃运动系统与鸡和小鼠的相似，除了面神经（nVII）和舌咽神经（nIX）鳃运动神经元的位置。对鳃运动神经元表达的基因进行发育分析表明，斑马鱼中nVII神经元位置的差异可能是细胞迁移所致。为深入了解这些神经元的组织和轴突发生的潜在机制，我们研究了神经元突变体中鳃运动通路的发育。valentino b337突变阻断了菱脑节5和6的形成，并严重影响nVII和nIX运动核的发育。cyclops b16突变删除了神经管中的腹侧中线细胞，并导致大多数鳃运动核和轴突通路严重紊乱。这些结果表明，菱脑节特异性信号和腹侧中线细胞在鳃运动通路的发育中起重要作用。
