@article {30153, title = {GABAergic inhibition of leg motoneurons is required for normal walking behavior in freely moving.}, journal = {Proc Natl Acad Sci U S A}, year = {2018}, month = {2018 Feb 13}, abstract = {

Walking is a complex rhythmic locomotor behavior generated by sequential and periodical contraction of muscles essential for coordinated control of movements of legs and leg joints. Studies of walking in vertebrates and invertebrates have revealed that premotor neural circuitry generates a basic rhythmic pattern that is sculpted by sensory feedback and ultimately controls the amplitude and phase of the motor output to leg muscles. However, the identity and functional roles of the premotor interneurons that directly control leg motoneuron activity are poorly understood. Here we take advantage of the powerful genetic methodology available into investigate the role of premotor inhibition in walking by genetically suppressing inhibitory input to leg motoneurons. For this, we have developed an algorithm for automated analysis of leg motion to characterize the walking parameters of wild-type flies from high-speed video recordings. Further, we use genetic reagents for targeted RNAi knockdown of inhibitory neurotransmitter receptors in leg motoneurons together with quantitative analysis of resulting changes in leg movement parameters in freely walkingOur findings indicate that targeted down-regulation of the GABAreceptor Rdl (Resistance to Dieldrin) in leg motoneurons results in a dramatic reduction of walking speed and step length without the loss of general leg coordination during locomotion. Genetically restricting the knockdown to the adult stage and subsets of motoneurons yields qualitatively identical results. Taken together, these findings identify GABAergic premotor inhibition of motoneurons as an important determinant of correctly coordinated leg movements and speed of walking in freely behaving.

}, issn = {1091-6490}, doi = {10.1073/pnas.1713869115}, author = {Gowda, Swetha B M and Paranjpe, Pushkar D and Reddy, O Venkateswara and Thiagarajan, Devasena and Palliyil, Sudhir and Reichert, Heinrich and VijayRaghavan, K} } @article {7042, title = {Drosophila larval to pupal switch under nutrient stress requires IP3R/Ca(2+) signalling in glutamatergic interneurons.}, journal = {Elife}, volume = {5}, year = {2016}, month = {2016 Aug 5}, abstract = {

Neuronal circuits are known to integrate nutritional information, but the identity of the circuit components is not completely understood. Amino acids are a class of nutrients that are vital for the growth and function of an organism. Here, we report a neuronal circuit that allows Drosophila larvae to overcome amino acid deprivation and pupariate. We find that nutrient stress is sensed by the class IV multidendritic cholinergic neurons. Through live calcium imaging experiments, we show that these cholinergic stimuli are conveyed to glutamatergic neurons in the ventral ganglion through mAChR. We further show that IP3R-dependent calcium transients in the glutamatergic neurons convey this signal to downstream medial neurosecretory cells (mNSCs). The circuit ultimately converges at the ring gland and regulates expression of ecdysteroid biosynthetic genes. Activity in this circuit is thus likely to be an adaptation that provides a layer of regulation to help surpass nutritional stress during development.

}, issn = {2050-084X}, doi = {10.7554/eLife.17495}, author = {Jayakumar, Siddharth and Richhariya, Shlesha and Reddy, O Venkateswara and Texada, Michael J and Hasan, Gaiti} } @article {3571, title = {Glial and neuronal Semaphorin signaling instruct the development of a functional myotopic map for Drosophila walking.}, journal = {Elife}, volume = {5}, year = {2016}, month = {2016}, abstract = {

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.

}, issn = {2050-084X}, doi = {10.7554/eLife.11572}, author = {Syed, Durafshan Sakeena and Gowda, Swetha B M and Reddy, O Venkateswara and Reichert, Heinrich and VijayRaghavan, K} } @article {734, title = {Neural control of wing coordination in flies.}, journal = {Curr Biol}, volume = {25}, year = {2015}, month = {2015 Jan 5}, pages = {80-6}, abstract = {

At the onset of each flight bout in flies, neural circuits in the CNS must rapidly integrate multimodal sensory stimuli and synchronously engage hinges of the left and right wings for coordinated wing movements. Whereas anatomical and physiological investigations of flight have been conducted on larger flies, molecular genetic studies in Drosophila have helped identify neurons that mediate various levels of flight control. However, neurons that might mediate bilateral coordination of wing movements to precisely synchronize left and right wing engagement at flight onset and maintain their movement in perfect coordination at rapid frequencies during flight maneuvers remain largely unexplored. Wing coordination could be directly modulated via bilateral sensory inputs to motoneurons of steering muscles and/or through central interneurons. Using a Ca(2+)-activity-based GFP reporter, we identified three flight-activated central dopaminergic interneurons in the ventral ganglion, which connect to and activate motoneurons that innervate a pair of direct-steering flight muscles. The activation of these newly identified dopaminergic interneurons is context specific. Whereas bilateral wing engagement for flight requires these neurons, they do not control unilateral wing extension during courtship. Thus, independent central circuits function in the context of different natural behaviors to control the motor circuit for Drosophila wing movement.

}, keywords = {Animals, Central Nervous System, Dopaminergic Neurons, Drosophila, Flight, Animal, Genes, Reporter, Male, Synapses, Wings, Animal}, issn = {1879-0445}, doi = {10.1016/j.cub.2014.10.069}, author = {Sadaf, Sufia and Reddy, O Venkateswara and Sane, Sanjay P and Hasan, Gaiti} }