Pike S H, Eisen J S
Institute of Neuroscience, University of Oregon, Eugene 97403.
J Neurosci. 1990 Jan;10(1):44-9. doi: 10.1523/JNEUROSCI.10-01-00044.1990.
Accurate pathfinding is a crucial step in formation of a functional nervous system. Individually identified zebrafish primary motoneurons undergo a stereotyped temporal sequence of axonal outgrowth and pathway selection during which their growth cones follow a common pathway to a "choice point" and then select divergent cell-specific pathways that lead to separate muscle territories. The characteristic sequence of cell-specific pathway selection raises the possibility that the sequence of growth cone arrival at the choice point might determine pathway selection. To test this idea, we ablated identified primary motoneurons by laser irradiation, labeled the remaining primary motoneuron in the same hemisegment with a fluorescent dye, and followed its development through the end of embryogenesis. We found that the growth cone of each primary motoneuron has an independent ability to pioneer the common pathway and select its appropriate cell-specific pathway, even in the absence of all other primary motoneurons in the same hemisegment.
精确的路径寻找是功能性神经系统形成过程中的关键一步。单个可识别的斑马鱼初级运动神经元经历轴突生长和路径选择的固定时间顺序，在此期间它们的生长锥沿着共同路径到达“选择点”，然后选择不同的细胞特异性路径，通向不同的肌肉区域。细胞特异性路径选择的特征顺序增加了一种可能性，即生长锥到达选择点的顺序可能决定路径选择。为了验证这一想法，我们通过激光照射消融已识别的初级运动神经元，用荧光染料标记同一半节段中剩余的初级运动神经元，并跟踪其发育直至胚胎发育结束。我们发现，即使同一半节段中没有所有其他初级运动神经元，每个初级运动神经元的生长锥都具有独立开拓共同路径并选择其合适的细胞特异性路径的能力。
