Uchida Atsuko, Brown Anthony
Center for Molecular Neurobiology and Department of Neuroscience, The Ohio State University, Columbus, OH 43210, USA.
Mol Biol Cell. 2004 Sep;15(9):4215-25. doi: 10.1091/mbc.e04-05-0371. Epub 2004 Jun 23.
We have investigated the movement of green fluorescent protein-tagged neurofilaments at the distal ends of growing axons by using time-lapse fluorescence imaging. The filaments moved in a rapid, infrequent, and asynchronous manner in either an anterograde or retrograde direction (60% anterograde, 40% retrograde). Most of the anterograde filaments entered the growth cone and most of the retrograde filaments originated in the growth cone. In a small number of cases we were able to observe neurofilaments reverse direction, and all of these reversals occurred in or close to the growth cone. We conclude that neurofilament polymers are delivered rapidly and infrequently to the tips of growing axons and that some of these polymers reverse direction in the growth cone and move back into the axon. We propose that 1) growth cones are a preferential site of neurofilament reversal in distal axons, 2) most retrograde neurofilaments in distal axons originate by reversal of anterograde filaments in the growth cone, 3) those anterograde filaments that do not reverse direction are recruited to form the neurofilament cytoskeleton of the newly forming axon, and 4) the net delivery of neurofilament polymers to growth cones may be controlled by regulating the reversal frequency.
我们通过延时荧光成像技术研究了绿色荧光蛋白标记的神经丝在生长轴突远端的运动情况。这些神经丝以快速、不频繁且异步的方式在顺行或逆行方向移动（60%顺行，40%逆行）。大多数顺行的神经丝进入生长锥，大多数逆行的神经丝起源于生长锥。在少数情况下，我们能够观察到神经丝改变方向，并且所有这些方向逆转都发生在生长锥内或其附近。我们得出结论，神经丝聚合物以快速且不频繁的方式被输送到生长轴突的末端，并且其中一些聚合物在生长锥内改变方向并向轴突内反向移动。我们提出：1）生长锥是轴突远端神经丝方向逆转的优先位点；2）轴突远端的大多数逆行神经丝起源于生长锥内顺行神经丝的方向逆转；3）那些不改变方向的顺行神经丝被募集以形成新形成轴突的神经丝细胞骨架；4）通过调节逆转频率可以控制神经丝聚合物向生长锥的净输送。
