Hall G F, Lee V M, Kosik K S
Department of Neurology (Neuroscience), Harvard Medical School and Center for Neurologic, Boston, MA.
Proc Natl Acad Sci U S A. 1991 Jun 1;88(11):5016-20. doi: 10.1073/pnas.88.11.5016.
Axotomy of giant lamprey (Petromyzon marinus) central neurons (anterior bulbar cells) close to their somata results in ectopic axon-like sprouting from the dendritic tips. Such sprouts first appear as swellings at the tips of a small subset of dendrites 2-3 weeks after "close" axotomy. We report here that immunocytochemical examination of these swellings reveals a structure and composition that differs from that of conventional growth cones; incipient sprouts contain many highly phosphorylated neurofilaments (NFs), little tubulin, and virtually no stable (acetylated) microtubules (MTs). The dendrites of anterior bulbar cells after close axotomy also show pronounced changes in NF protein and tubulin staining patterns prior to the emergence of sprouts from the dendrites. The amount of tyrosinated tubulin increases greatly; this rise is tightly coupled to the appearance of highly phosphorylated NFs and the loss of nonphosphorylated NFs in the dendrites. Acetylated tubulin is generally reduced after close axotomy and is selectively lost from dendrites that gave rise to sprouts. These changes indicate that an invasion of the dendrites by phosphorylated NFs may be linked to the destabilization of dendritic MTs, and in some dendrites this may lead to a marked loss of stable MTs, which is correlated with the emergence of NF-filled sprouts from the dendritic tips.
对海七鳃鳗（Petromyzon marinus）靠近其胞体的中枢神经元（前延髓细胞）进行轴突切断，会导致树突尖端出现异位的轴突样芽生。在“近端”轴突切断后2至3周，这些芽最初表现为一小部分树突尖端的肿胀。我们在此报告，对这些肿胀进行免疫细胞化学检查发现，其结构和组成与传统生长锥不同；初期芽生包含许多高度磷酸化的神经丝（NFs），微管蛋白很少，几乎没有稳定的（乙酰化）微管（MTs）。近端轴突切断后，前延髓细胞的树突在树突芽生出现之前，NF蛋白和微管蛋白染色模式也显示出明显变化。酪氨酸化微管蛋白的量大幅增加；这种增加与树突中高度磷酸化的NFs的出现以及非磷酸化NFs的丢失紧密相关。近端轴突切断后，乙酰化微管蛋白通常减少，并从产生芽生的树突中选择性丢失。这些变化表明，磷酸化的NFs侵入树突可能与树突MTs的不稳定有关，在某些树突中，这可能导致稳定MTs的显著丢失，这与树突尖端出现充满NFs的芽生相关联。
