Biology subjects

Sitaula, A.

Publications and source records attributed to Sitaula, A..

3 recordsLinked to original sources

bioRxiv2026

Reconfiguration of Premotor Excitation and Inhibition Drives Behavior-Specific Protopodium Dynamics in Drosophila Larvae

Animals use shared muscles and motor neurons to generate distinct movements, but how premotor circuits differentially recruit these neuromuscular components remains unclear. Drosophila larvae crawl forward and backward using overlapping motor pools, yet the timing of ventral oblique (VO) muscle activity differs between these behaviors. Here, we show that VO muscles are major contributors to the movement of protopodia, limb-like structures that help larvae interact with the crawling surface. Muscle imaging, perturbation, and modeling indicate that VO activity is particularly important for protopodium folding, whereas contractions of both VO and ventral longitudinal (VL) muscles contribute to protopodium stride length and crawling efficiency. We identify a tri-segmental premotor motif--comprising excitatory (A27h, A18b3) and inhibitory (A06c) neurons--that shapes VO timing during forward crawling. A06c exhibits two activity peaks during forward fictive locomotion, defining a constrained window of VO MN activation, whereas during backward locomotion the early A06c peak is absent and the excitatory PMNs A27h and A18b3 are inactive. Disrupting this motif shifts VO activity earlier, reduces intersegmental timing delays, increases temporal overlap of VO activity, and impairs forward protopodium folding, stride, and crawling efficiency. These findings show how premotor excitation and inhibition coordinate muscle timing to shape locomotor mechanics.

neuroscience↗

bioRxiv2025

A Drosophila Tonic Motor Neuron Reinnervates Ectopic Muscles Fully Deprived of Native Tonic and Phasic Inputs

Motor neurons (MNs) form precise neuromuscular junctions (NMJs) during development, but the extent to which individual MNs can reinnervate fully denervated muscles in vivo remains poorly understood. In the Drosophila larva, each muscle is co- innervated by a tonic and a phasic glutamatergic MN. Here, we show that the tonic MN1 undergoes robust heterosynaptic sprouting and forms ectopic NMJs when neighboring muscles are deprived of both their native tonic and phasic inputs. This structural plasticity is not induced by silencing, but instead requires the physical ablation of adjacent MNs. Live imaging of the same MN1 axons in individual animals reveals that sprouting initiates early and expands progressively across larval stages. In contrast, phasic MNs show minimal remodeling, indicating that tonic MNs possess a greater intrinsic capacity for neuroplasticity. Notably, as MN1 establishes new synapses on targets it does not normally innervate, it redistributes pre-synaptic territory across both native and ectopic muscles. These findings identify a subtype-specific, injury-induced rewiring program in an intact motor circuit.

neuroscience↗

bioRxiv2025

Motor Neurons Decode Cholinergic Inputs via Spatially Distinct nAChR Subunits to Drive Locomotion in Drosophila larvae

Neural circuits consist of neurons that differ not only in their neurotransmitter identities but also in the types and subcellular localization of neurotransmitter receptors (NRs) they express. This receptor diversity enables distinct responses to the same neurotransmitter, highlighting the need to understand NR distribution and function to fully interpret circuit logic. Here, we focus on nicotinic acetylcholine receptors (nAChRs), the primary mediators of fast excitatory transmission in the Drosophila central nervous system (CNS). Functional nAChRs are pentamers assembled from a pool of 10 subunits (1-7, {beta}1-{beta}3), yet their in vivo expression and function remain poorly defined. We used T2A-Gal4 lines and endogenous protein tagging to examine nAChR expression in larval motor neurons (MNs) and identified eight subunits (1-3, 5-7, {beta}1, {beta}2) expressed in these cells. MN-specific knockdown of individual subunits caused distinct locomotor defects, indicating their functional importance. Co-localization analysis revealed some subunit pairs are frequently co-expressed at the same synapses, while others localize to distinct subcellular domains. Supporting this, double knockdown of co-localized subunits did not worsen locomotor phenotypes compared to single knockdowns, whereas knockdown of non-co-localized subunit pairs produced additive defects. These results suggest that different nAChR subtypes are strategically positioned in discrete synaptic domains within single MNs, where they serve non-redundant roles. Our findings provide new insight into the spatial organization and functional diversity of nAChRs in motor circuits that drive locomotion. Significance StatementMotor circuits rely on precise neurotransmitter signaling, yet the diversity and subcellular organization of neurotransmitter receptors remain poorly understood. Using Drosophila larvae, we show that motor neurons express multiple nicotinic acetylcholine receptor (nAChR) subunits, which localize to distinct synaptic domains and play non-redundant roles in locomotion. These findings reveal a previously underappreciated level of receptor compartmentalization within single neurons and demonstrate that spatially organized nAChRs are essential for coordinated movement. By integrating genetic, imaging, and behavioral approaches, our work provides a new framework for understanding how receptor diversity shapes motor output and highlights the importance of mapping receptor localization to decode circuit function in both health and disease.

neuroscience↗