Control of directional change after mechanical stimulation in Drosophila

Abstract

BackgroundProper adjustment of moving direction after external mechanical stimulation is essential for animals to avoid danger (e.g. predators), and thus is vital for survival. This process involves sensory inputs, central processing and motor outputs. Recent studies have made considerable progress in identifying mechanosensitive neurons and mechanosensation receptor proteins. Our understandings of molecular and cellular mechanisms that link mechanosensation with the changes in moving direction, however, remain limited.ResultsIn this study, we investigate the control of movement adjustment in Drosophila. In response to gentle touch at the anterior segments, Drosophila larvae reorient and select a new direction for forward movement. The extent of change in moving direction is correlated with the intensity of tactile stimuli. Sensation of gentle touch requires chordotonal organs and class IV da neurons. Genetic analysis indicates an important role for the evolutionarily conserved immunoglobulin (Ig) superfamily protein Turtle (Tutl) to regulate touch-initiated directional change. Tutl is required specifically in post-mitotic neurons at larval stage after the completion of embryonic development. Circuit breaking analysis identified a small subset of Tutl-positive neurons that are involved in the adjustment of moving direction.ConclusionWe identify Tutl and a small subset of CNS neurons in modulating directional change in response to gentle touch. This study presents an excellent starting point for further dissection of molecular and cellular mechanisms controlling directional adjustment after mechanical stimulation.

The TRP Channels Pkd2, NompC, and Trpm Act in Cold-Sensing Neurons to Mediate Unique Aversive Behaviors to Noxious Cold in Drosophila

“…In the global assay, larvae were acclimated to a 25 ºC metal plate (Movie S1), then transferred to a cold or cool surface (4–16 °C) (Figure 1A). Two unique behaviors were observed, distinct from normal peristaltic locomotion (Movie S1), gentle touch behaviors [32, 33], and aversive rolling to noxious heat [11, 24] or force [13, 17, 18, 24]. The cold-evoked behaviors were a 45–90 ° head and/or tail raise (HTR) or a contraction (CT) of the head and tail towards the middle of the body (Movie S2).…”

“…One of the primary reactions to gentle touch is a head withdrawal (HW) [32, 33], which is like an asymmetric CT. To clarify how these cells might distinguish between cold and gentle touch we varied the dose of optogenetic light activating CIII neurons, to see if a particular activation level evoked either HW or CT (Figure 7A, Movie S6). Optogenetic activation of CIII neurons at the highest dose, resulted in CT almost exclusively (Figure 7A).…”

“…The primary cold-evoked behavior, CT, is unlike larval responses to other types of nociceptive [11, 13, 17, 18, 24] and innocuous stimuli [19, 20, 32, 33]. Several lines of evidence indicate that CIII neurons are cold nociceptors.…”

Neuromodulators signal through astrocytes to alter neural circuit activity and behaviour

“…We therefore used a gentle anterior touch assay 17 to examine the role of astrocyte Ca 2+ signaling in larval startle-induced behaviors. Crawling larvae touched anteriorly with a hair responded by pausing and continuing forward (Type I response), or by moving backward and executing an escape response (Type II response) (Extended Data Fig.…”

Novel Assay for Cold Nociception in <em>Drosophila</em> Larvae

“…While class IV neurons are required for larval lateral body roll responses to high temperatures or harsh mechanical stimuli 4 , class III neurons are required for gentle touch responses 9,10 and are not only activated by cold, but also are required for the cold-evoked behavioral responses 7 . Both class III and class IV neurons utilize discrete transient receptor potential (TRP) channels to facilitate behavioral responses to noxious 7,11,18 and non-noxious stimuli 9,10,17,19 . Further, larval nociception is sensitized following injury, at the cellular 20 and behavioral levels 12,21 .…”