![]() Previous studies have shown that Slit also helps to position the termini of axons (sites of synaptic output), independent of their synaptic partners. These proteins act as global guidance cues and exert their effects via distinct signaling pathways using receptors called Roundabout and Frazzled, respectively. The precise targeting of dendrites along the mediolateral axis is controlled by the signaling molecules Slit and Netrin, which are secreted by midline cells. These motoneurons generate a ‘myotopic map’ by targeting the growth of their dendrites (sites of synaptic input) into discrete territories during development. Here, we show that the leg motoneurons of Drosophila organize their dendrites within the central nervous system in a way that reflects the position of the muscles they innervate. Much less is known about the anatomical organization and development of motor systems. These results reveal that dendritic targeting plays a major role in the formation of myotopic maps and suggests that the coordinate spatial control of both pre- and postsynaptic elements by global neuropilar signals may be an important mechanism for establishing the specificity of synaptic connections.ĭuring development the axons of sensory neurons generate highly ordered ”sensory maps„ within the nervous system that represent specific qualities of the environment. We demonstrate that the medio-lateral positioning of motoneuron dendrites in the leg neuropil is controlled by the midline signalling systems Slit-Robo and Netrin-Fra. Our developmental analysis of dendrite growth reveals that this myotopic map is generated by targeting. Thus the cellular distinctions in peripheral targets and central dendritic domains, which make up the myotopic map, are linked to the birth-order of these motoneurons. A single postembryonic neuroblast sequentially generates different leg motoneuron subtypes, starting with those innervating proximal targets and medial neuropil regions and producing progeny that innervate distal muscle targets and lateral neuropil later in the lineage. Here we reveal that this fundamental organizational principle exists in adult Drosophila, where the dendrites of leg motoneurons also generate a myotopic map. Within the embryonic nervous system of Drosophila motoneuron dendrites are organized topographically as a myotopic map that reflects their pattern of innervation in the muscle field. Neural maps are emergent, highly ordered structures that are essential for organizing and presenting synaptic information. ![]()
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