Shirasaki R, Tamada A, Katsumata R, Murakami F
Department of Biophysical Engineering, Faculty of Engineering Science, Osaka University, Japan.
Neuron. 1995 May;14(5):961-72. doi: 10.1016/0896-6273(95)90334-8.
To elucidate guidance mechanisms of brain commissural axons, we examined the navigation of cerebellofugal axons. Axons were labeled by implantation of the fluorescent tracer Dil into the cerebellar plate (CP) of fixed, flat whole-mount embryonic rat brain. Axons initially grew straight toward the ventral midline floor plate (FP) in the rostral hindbrain and then, after crossing it, made a right-angled turn to grow either caudally or rostrally along the longitudinal axis. In collagen gel culture, CP axons showed directed growth toward both FP explants and heterologous cells expressing netrin-1, a FP-derived chemoattractant for spinal commissural axons. These results suggest that CP axons are guided to the midline by FP-derived chemoattractant(s) and then reoriented, possibly by another guidance cue, for longitudinal extension. Considering that the basic structures of the neural tube, including the FP, extend up to the caudal diencephalon, these results suggest that common guidance mechanisms operate for ventrally decussating commissural axons in both the brain and spinal cord.
为了阐明脑连合轴突的导向机制，我们研究了小脑传出轴突的导航。通过将荧光示踪剂Dil植入固定的扁平整装胚胎大鼠脑的小脑板（CP）来标记轴突。轴突最初在 Rostral 后脑向腹侧中线底板（FP）笔直生长，然后在穿过它之后，进行直角转弯，沿纵轴尾侧或 Rostral 生长。在胶原凝胶培养中，CP 轴突显示出向 FP 外植体和表达 netrin-1 的异源细胞的定向生长，netrin-1 是一种源自 FP 的脊髓连合轴突化学引诱剂。这些结果表明，CP 轴突被源自 FP 的化学引诱剂引导至中线，然后可能通过另一种导向线索重新定向以进行纵向延伸。考虑到神经管的基本结构，包括 FP，延伸至尾侧间脑，这些结果表明，脑和脊髓中腹侧交叉连合轴突存在共同的导向机制。
