Syed Durafshan Sakeena, Gowda Swetha B M, Reddy O Venkateswara, Reichert Heinrich, VijayRaghavan K
National Centre for Biological Sciences, Tata Institute of Fundamental Research, Bangalore, India.
Manipal University, Manipal, India.
Elife. 2016 Feb 29;5:e11572. doi: 10.7554/eLife.11572.
Motoneurons developmentally acquire appropriate cellular architectures that ensure connections with postsynaptic muscles and presynaptic neurons. In Drosophila, leg motoneurons are organized as a myotopic map, where their dendritic domains represent the muscle field. Here, we investigate mechanisms underlying development of aspects of this myotopic map, required for walking. A behavioral screen identified roles for Semaphorins (Sema) and Plexins (Plex) in walking behavior. Deciphering this phenotype, we show that PlexA/Sema1a mediates motoneuron axon branching in ways that differ in the proximal femur and distal tibia, based on motoneuronal birth order. Importantly, we show a novel role for glia in positioning dendrites of specific motoneurons; PlexB/Sema2a is required for dendritic positioning of late-born motoneurons but not early-born motoneurons. These findings indicate that communication within motoneurons and between glia and motoneurons, mediated by the combined action of different Plexin/Semaphorin signaling systems, are required for the formation of a functional myotopic map.
运动神经元在发育过程中获得适当的细胞结构，以确保与突触后肌肉和突触前神经元建立连接。在果蝇中，腿部运动神经元被组织成一个肌位图谱，其中它们的树突域代表肌肉场。在这里，我们研究这种肌位图谱中与行走相关的各个方面发育的潜在机制。一项行为筛选确定了信号素（Sema）和丛状蛋白（Plex）在行走行为中的作用。通过对这种表型的解读，我们发现基于运动神经元的出生顺序，PlexA/Sema1a以不同的方式介导运动神经元轴突在股骨近端和胫骨远端的分支。重要的是，我们发现神经胶质细胞在特定运动神经元树突定位中具有新的作用；PlexB/Sema2a是晚期出生的运动神经元树突定位所必需的，但不是早期出生的运动神经元所必需的。这些发现表明，不同丛状蛋白/信号素信号系统的联合作用介导的运动神经元内部以及神经胶质细胞与运动神经元之间的通讯，对于功能性肌位图谱的形成是必需的。
