Pioneer growth cone morphologies reveal proximal increases in substrate affinity within leg segments of grasshopper embryos
Pioneer growth cone morphologies reveal proximal increases in substrate affinity within leg segments of grasshopper embryos
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DOI：
10.1523/jneurosci.06-02-00364.1986
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发表时间：
1986-02
期刊：
影响因子：
--
通讯作者：
M. Caudy;D. Bentley
中科院分区：
文献类型：
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作者：
M. Caudy;D. Bentley
我们比较了大约5000个抗体标记的传入先驱生长锥的形态，这些生长锥沿着它们在蚱蜢胚胎腿上皮上的特征路径固定在不同的生长阶段，并使用生长锥形态作为体内上皮基质对先驱生长锥的亲和力差异的指标。不同部位的枝芽生长锥形态差异显著，同一部位的枝芽在不同分化阶段的生长锥形态差异显著。生长锥的特征是沿体节边界沿着周向延伸枝和片层，并且丝状伪足和片层在那里保留（或延伸）更长。在它们接触相对分化良好的体节边界的地方，生长锥也突然沿圆周方向重新定向.在肢节的近端区域，生长锥始终具有高度的分支和层状结构;先前形成的轴突也延伸二级分支，并随着发育的进展而扩散。在肢体节段的远端区域的所有阶段观察到这些形态的低发生率。因此，神经元形态在空间和时间上与肢体分割的分化相关。这些结果表明：详细的生长锥形态是一个可靠的指标，外在的指导线索的差异。传入先锋生长锥的上皮基质的亲和力增加近端段内，在段边界处的峰值。(This亲和力可以基于粘附分子的表面密度或基于主动调节生长锥延伸的非粘附分子。增加上皮细胞的亲和力段内似乎作为一个近端的指导线索传入先锋生长锥。观察到先锋生长锥在近端定位的路标细胞分化太晚而不能引导它们的情况下向近端导航。
We have compared the morphologies of approximately 5000 antibody- labeled afferent pioneer growth cones fixed at various stages of growth along their characteristic path over the epithelium in the legs of grasshopper embryos, and have used growth cone morphology as an indicator of differences in the affinity of the epithelial substrate for pioneer growth cones in vivo. Growth cone morphologies differ markedly between different locations in limb buds, and also in the same location in limbs at different stages of differentiation. Growth cones characteristically extend branches and lamellae circumferentially along segment boundaries, and filopodia and lamellae are retained (or extended) longer there. Where they contact a relatively well- differentiated segment boundary, the growth cones also abruptly reorient circumferentially. In the proximal regions of limb segments, growth cones consistently have a high degree of branching and lamellae; previously formed axons also extend secondary branches and spread there as development progresses. Low incidence of these morphologies is observed at all stages in the distal regions of limb segments. Thus, neuronal morphologies correlate both spatially and temporally with the differentiation of limb segmentation. These results suggest the following: Detailed growth cone morphology is a reliable indicator of differences in extrinsic guidance cues. The affinity of the epithelial substrate for afferent pioneer growth cones increases proximally within segments, with a peak at the segment boundary. (This affinity could be based on surface density of adhesion molecules or on nonadhesive molecules that actively regulate growth cone extension.) Increasing epithelial affinity within segments appears to act as a proximal guidance cue for afferent pioneer growth cones. Pioneer growth cones are observed to navigate proximally in circumstances where proximally located guidepost cells differentiate too late to guide them.