RT Journal Article SR Electronic T1 Glial and neuronal Semaphorin signaling instruct the development of a functional myotopic map for Drosophila walking JF bioRxiv FD Cold Spring Harbor Laboratory SP 027375 DO 10.1101/027375 A1 Durafshan Sakeena Syed A1 BM Swetha A1 O. Venkateswara Reddy A1 Heinrich Reichert A1 VijayRaghavan K. YR 2015 UL http://biorxiv.org/content/early/2015/09/24/027375.abstract AB 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 (Serna) 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.