Morphology of pioneer and follower growth cones in the developing cerebral cortex.
Morphology of pioneer and follower growth cones in the developing cerebral cortex.
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发育中的大脑皮层中先驱和追随生长锥的形态。
DOI：
10.1002/neu.480220608
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发表时间：
1991
期刊：
影响因子：
--
通讯作者：
McConnell,SK
中科院分区：
文献类型：
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作者：
Kim,GJ;Shatz,CJ;McConnell,SK
在无脊椎动物和脊椎动物的神经系统发育中，神经元必须发展精确的轴突连接。这两种动物都使用的一种策略是产生一类特殊的神经元，其轴突是这些细胞与其靶细胞之间的第一条通路的“先驱”。在发育中的哺乳动物端脑中，亚板神经元（其是在发育中产生的第一批神经元之一）在深层皮质层5和6的神经元产生之前将轴突延伸到长距离的皮质下目标。第5层和第6层神经元的轴突随后遵循类似的途径形成向丘脑和顶盖的永久性皮质下投射，此后绝大多数亚板神经元死亡。这些结果产生的假设，亚板轴突可能实际上需要的第5层和第6层神经元的轴突，以支配其适当的皮层下的目标。生长锥的复杂性以前与轴突决策相关：生长锥形态的差异已经在领先轴突与跟随轴突的比较中被注意到（LoPresti，Macagno和Levinthal，1973; Nordlander，1987; Yaginuma，Homma，Kunzi和Oppenheim，1991），以及沿着轴突通路的选择点（Raper，Bastiani和Goodman，1983; Tosney和Landmesser，1985; Caudy和Bentley，1986 a，B; Bovolenta和Mason，1987; Holt，1989; Bovolenta和Dodd，1990; Yaginuma等人，1991年）。因此，作为解决深层神经元的轴突是否简单地跟随亚板轴突到达其目标的问题的第一步，我们已经研究了皮质生长锥在不同点沿着皮质丘脑通路和在不同的发展阶段的形态。本文用荧光亲脂性示踪剂1，1-双十八烷基-3，3，3′，3′-四甲基吲哚羰花青高氯酸盐（Dil）对雪貂和猫胚胎24 ~ 50天的脑进行了研究。生长锥绘制，并通过计算丝状伪足和计算其表面积来定量测量其复杂性。没有发现形态学差异之间的生长锥在不同点沿着皮质丘脑通路在给定的年龄。然而，属于早期产生的细胞（可能是subplate神经元）的生长锥明显比后来产生的皮层神经元的生长锥更大，更复杂。这一证据是一致的建议，基板生长锥积极开拓皮质丘脑通路，并遵循它的第5和第6层神经元的轴突。
In the developing nervous systems of both invertebrates and vertebrates, neurons must develop precise sets of axonal connections. One strategy used by both orders of animals is to generate a special class of neurons whose axons “pioneer” the first pathways between these cells and their targets. In the developing mammalian telencephalon, the subplate neurons (which are among the first neurons to be generated in development) extend axons to long-distance subcortical targets before the neurons of the deep cortical layers 5 and 6 have been generated. The axons of layer 5 and 6 neurons later follow a similar pathway to form permanent subcortical projections to the thalamus and tectum, and thereafter the vast majority of subplate neurons die. These results have generated the hypothesis that subplate axons may actually be required for the axons of layer 5 and 6 neurons to innervate their appropriate subcortical targets. The complexity of growth cones has previously been correlated with axonal decision making: differences in growth cone morphologies have been noted in comparisons of leading versus following axons (LoPresti, Macagno, and Levinthal, 1973; Nordlander, 1987; Yaginuma, Homma, Kunzi, and Oppenheim, 1991), and at choice points along axon pathways (Raper, Bastiani, and Goodman, 1983; Tosney and Landmesser, 1985; Caudy and Bentley, 1986a, b; Bovolenta and Mason, 1987; Holt, 1989; Bovolenta and Dodd, 1990; Yaginuma et al., 1991). Thus, as a first step toward addressing the question of whether the axons of deep-layer neurons simply follow subplate axons to their targets, we have studied the morphology of cortical growth cones at various points along the corticothalamic pathway and at different stages of development. We examined the brains of fetal ferrets and cats at ages ranging from embryonic days (E) 24 to E50, using the fluorescent lipophilic tracer 1, 1-dioctadecyl-3, 3, 3′, 3′-tetramethyl indocarbocyanine perchlorate (Dil) to reveal the axons and growth cones of cortical neurons. Growth cones were drawn, and quantitative measurements of their complexity were made by counting filopodia and calculating their surface area. No morphological differences were found among growth cones at different points along the corticothalamic pathway at a given age. However, growth cones belonging to early-generated cells (likely to be subplate neurons) are significantly larger and more complex than are the growth cones of later-generated cortical neurons. This evidence is consistent with the suggestion that subplate growth cones actively pioneer the corticothalamic pathway, and that the axons of layer 5 and 6 neurons follow it.