Changes in microtubule number and length during axon differentiation
Changes in microtubule number and length during axon differentiation
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DOI：
10.1523/jneurosci.14-05-02818.1994
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发表时间：
1994-05
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影响因子：
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通讯作者：
Wenqian Yu;P. Baas
中科院分区：
文献类型：
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作者：
Wenqian Yu;P. Baas
培养的海马神经元最初延伸出几个大约20微米长的小突起。第一个比其他过程长约10微米的小过程将继续快速增长，并成为轴突(Goslin和Banker，1989)。我们试图定义在轴突分化过程中微管(MT)阵列的变化。从理论上讲，轴突分化可能涉及MT数量的增加、MT长度的增加或两者的某种组合。为了解决这个问题，我们首先从一个轴突尚未分化的细胞连续重建了一个小突起的整个MT阵列。这个小过程包含182个MT，长度从0.14微米到20.09微米不等。MT平均长度为3.87+/-3.83微米，MT总长度为704微米。然后，我们重建了一个小突起的MT阵列和一个经历了轴突分化的细胞的56微米轴突。次要工艺包含157个MT，其长度从0.24到17.95微米不等。MT平均长度为3.91+/-4.84微米，MT总长度为600微米。轴突含有1430个线粒体，长度从0.05微米到40.14微米不等。MT平均长度为4.02+/-5.28微米，MT总长度为5750微米。这些数据表明，在轴突分化过程中，MTS向更短和更长的方向移动，但平均MT长度几乎没有变化。因此，现有MTS的延长不能解释MT阵列的主要扩张，即当一个小突起变成轴突时发生的。相反，当一个微小的突起分化并生长成我们分析的长度的轴突时，MT的数量增加了大约10倍。基于这些数据，我们得出结论，小突起的MT阵列在分化为轴突时实质上是扩张的，这种扩张发生的主要机制是大量增加新的MT。
Hippocampal neurons in culture initially extend several minor processes that are approximately 20 microns in length. The first minor process to grow approximately 10 microns longer than the others will continue to grow rapidly and become the axon (Goslin and Banker, 1989). We sought to define changes in the microtubule (MT) array that occur during axon differentiation. In theory, axon differentiation could involve an increase in MT number, MT length, or some combination of both. To address this issue, we first serially reconstructed the entire MT array of a minor process from a cell whose axon had not yet differentiated. This minor process contained 182 MTs that ranged in length from 0.14 to 20.09 microns. The average MT length was 3.87 +/- 3.83 microns, and the total MT length was 704 microns. We then reconstructed the MT arrays of a minor process and the 56 microns axon from a cell that had undergone axon differentiation. The minor process contained 157 MTs that ranged in length from 0.24 to 17.95 microns. The average MT length was 3.91 +/- 4.84 microns, and the total MT length was 600 microns. The axon contained 1430 MTs that ranged in length from 0.05 to 40.14 microns. The average MT length was 4.02 +/- 5.28 microns, and the total MT length was 5750 microns. These data indicate that a shift occurs toward shorter as well as longer MTs, but that virtually no change in average MT length occurs during axon differentiation. Thus, elongation of existing MTs cannot account for the major expansion of the MT array that occurs as a minor process becomes an axon. In contrast, the number of MTs increases by approximately 10-fold as a minor process differentiates and grows into an axon of the length we analyzed. Based on these data, we conclude that the MT array of a minor process is substantially expanded as it differentiates into an axon, and that the principal mechanism by which this expansion occurs is the copious addition of new MTs.