The present study aimed to assess spinal tract formation in neurons originating from cervical (C7), brachial (C14), and thoracic (T4) regions, with the lumbar (LS2) region as a reference, in a chick embryo. For the assessment of the spinal tracts, we introduced a vector expressing human placental alkaline phosphatase into progenitor cells generated after neural tube closure and belonging to the above segments, using in ovo electroporation. The ascending axons took primarily similar paths: dorsal commissural, ventral commissural, and dorsal non-commissural paths, with some variance depending on their originating segments. Some populations of non-commissural neurons later extended their axons following a ventral path. The elongation rates of these axons are primarily constant and tended to increase over time; however, some variations depending on the originating segments were also observed. Some of the dorsally ascending axons entered into the developing cerebellum, and spinocerebellar neurons originating from T4 projected their axons into the cortex of the cerebellum differently from those from LS2. These results unveil an overall picture of early ascending spinal tract formation.

本研究旨在评估鸡胚中源自颈椎 (C7)、肱骨 (C14) 和胸椎 (T4) 区域的神经元的脊髓束形成，腰椎 (LS2) 区域作为参考。为了评估脊髓束，我们将表达人胎盘碱性磷酸酶的载体引入神经管闭合后产生的属于上述节段的祖细胞中，使用ovo电穿孔。上行轴突主要采取相似的路径：背侧连合、腹侧连合和背侧非连合路径，根据它们的起源节段有一些差异。一些非连合神经元群后来沿着腹侧路径延伸它们的轴突。这些轴突的伸长率主要是恒定的，并且会随着时间的推移而增加。但是，也观察到了一些取决于原始段的变化。一些背侧上行轴突进入发育中的小脑，来自 T4 的脊髓小脑神经元将它们的轴突投射到小脑皮层，这与来自 LS2 的不同。这些结果揭示了早期上行脊髓束形成的总体情况。