Extensive branching creates the complex dendritic arbor of mammalian CNS neurons but capturing the complete process of branch formation with time-lapse recordings has been challenging. Here, we report that application of BMP7 to cultured hippocampal neurons accelerated dendritic growth sufficiently to document branches forming in less than 20 h via frequent time-lapse imaging (10-min intervals). In these recordings, most branches emerged as collateral sprouts from the shaft of a parent branch. Analysis of the recordings showed that filopodia were abundant and formed transiently throughout the length of dendrites but among these, only a small subset occurred at sites where branches later emerged. Conversely, formation of lamellipodia was rare and coincided with sites where collateral branches emerged. This pattern suggests that lamellipodial structures act as an important intermediate form of cytoskeletal remodeling related to a cellular commitment to branch, whereas filopodia appear to be related to events prior to such commitment.

中文翻译：

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瞬时片状伪足预测海马神经元树突分支形成的位点

广泛的分支创造了哺乳动物中枢神经系统神经元的复杂树突乔木，但用延时记录捕捉分支形成的完整过程一直具有挑战性。在这里，我们报告将 BMP7 应用于培养的海马神经元加速了树突生长，足以通过频繁的延时成像（10 分钟间隔）记录在不到 20 小时内形成的分支。在这些记录中，大多数分支从父分支的轴上长出侧枝芽。对录音的分析表明，丝状伪足在整个树突的长度上都非常丰富并且短暂地形成，但其中只有一小部分发生在分支后来出现的位置。相反，片状伪足的形成是罕见的，并且与侧枝出现的地点相吻合。