Activity-dependent regulation of synaptic size in Drosophila neuromuscular junctions.
Activity-dependent regulation of synaptic size in Drosophila neuromuscular junctions.
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DOI：
10.1002/neu.20292
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发表时间：
2006-08
期刊：
影响因子：
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通讯作者：
Hiroaki Nakayama;H. Kazama;A. Nose;T. Morimoto-Tanifuji
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作者：
Hiroaki Nakayama;H. Kazama;A. Nose;T. Morimoto-Tanifuji
神经发育的一个基本问题是神经元如何形成适当大小的突触，以便在神经回路中有效地传递信息。在此，我们研究了果蝇神经肌肉连接（NMJs）发育过程中突触和突触后细胞大小相关的机制。为了做到这一点，我们使用了一个独特的系统，其中两个相邻的肌肉（M6和M7）由相同的神经元支配。在成熟的NMJs中，M6上的突触大小通常大于M7，这与肌肉体积的差异有关；这保证了两块肌肉的收缩程度相同，我们把这种对应称为“匹配”。我们发现，尽管肌肉体积存在差异，但在孵化后8 h的幼虫中匹配明显，而在新孵化的幼虫中不匹配。当感觉输入被感觉神经元中破伤风毒素的表达抑制时，尽管突触能够生长，但匹配并没有发生。运动神经元活动的抑制也抑制了匹配。这些结果表明，匹配是通过调节M6和M7的突触生长速率来诱导的，这种方式依赖于经验和活动。从突触后细胞到突触前细胞的逆行信号似乎最有可能传达肌肉细胞大小的信息。因此，我们研究了NMJs中逆行信号的候选，BMP信号是否参与匹配。然而，在BMP II型受体基因突变体中，对配对没有影响，这表明除了BMP信号外，其他经验驱动的机制也参与了突触的正常发育。
One of the fundamental questions in neural development is how neurons form synapses of the appropriate size for the efficient transfer of information across neural circuits. Here we investigated the mechanisms that bring about the size correlation between synapses and postsynaptic cells during development of Drosophila neuromuscular junctions (NMJs). To do this, we made use of a unique system in which two neighboring muscles (M6 and M7) are innervated by the same neurons. In mature NMJs, synaptic size on M6 is normally larger than that on M7, in accordance with the difference in muscle volume; this ensures the same extent of contraction of both muscles, and we refer to this correspondence as "matching". We found that matching was apparent in larvae 8 h after hatching, but not in newly hatched larvae despite the difference in muscle volume. When sensory inputs were suppressed by the expression of tetanus toxin in sensory neurons, matching did not occur, although synapses were able to grow. Matching was also suppressed by the inhibition of motoneuronal activity. These results suggest that matching is induced by regulating the rate of synaptic growth on M6 and M7 in an experience- and activity-dependent manner. It seems most likely that retrograde signals from the postsynaptic to the presynaptic cell convey the information about muscle cell size. We thus examined whether a candidate of retrograde signaling in NMJs, BMP signaling, is involved in matching. However, there was no effect on matching in BMP type II receptor gene mutants, suggesting that other experience-driven mechanisms besides BMP signaling are involved in the proper development of synapses.