The centrosomes of neurons do not nucleate microtubules (MTs). It is not well known where MTs are nucleated in neurons. We performed MT regrowth experiments in primary cultured cortical neurons from mice. After cold‐nocodazole depolymerization of MTs in neurons at 3 days in vitro (DIV), we observed numerous short MTs that regenerated in the cytoplasm; they were roughly equal in length and randomly oriented. Gamma‐tubulin and MZT2 were detected at one end of these MTs, indicating that the short MTs were nucleated by γ‐tubulin‐ring complexes; the Golgi apparatus was not the origin site of their nucleation. The ratio of MT‐regenerating cells, the density of regenerated MTs, and their lengths decreased at 7 DIV. Pretreatment of neurons with protein‐kinase inhibitors, K‐252a, staurosporine, or H7 diminished the length of the regenerated MTs, while pretreatment of neurons with brain‐derived neurotrophic factor increased the length of regenerated MTs. These results support the idea that short MTs with mixed orientations are transiently generated in the cytoplasm of differentiating neurons, and that they are possibly transported into dendrites to provide seeds for MTs with mixed polarity.

中文翻译：

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发育中的皮质神经元细胞质中的微管成核及其受脑源性神经营养因子的调节。

神经元的中心体不使微管（MTs）成核。尚不清楚MT在神经元中有核的位置。我们在小鼠原代培养的皮质神经元中进行了MT再生长实验。在体外第3天（DIV）神经元的MT的冷诺考达唑解聚后，我们观察到许多在细胞质中再生的短MT。它们的长度大致相等，方向随机。在这些MT的末端检测到γ-微管蛋白和MZT2，表明短的MT被γ-微管蛋白环复合物成核。高尔基体不是它们成核的起源点。MT再生细胞的比例，再生MT的密度及其长度在7 DIV时降低。用蛋白激酶抑制剂K-252a，星形孢菌素或H7预处理神经元可减少再生MT的长度，而用脑源性神经营养因子预处理神经元会增加再生MT的长度。这些结果支持这样的想法，即在分化的神经元的细胞质中短暂产生具有混合方向的短MT，并且它们有可能被转运到树突中为具有混合极性的MT提供种子。