Biology subjects

Grueber, W. B.

Publications and source records attributed to Grueber, W. B..

8 recordsLinked to original sources

bioRxiv2024

Mechanisms of gas sensing by internal sensory neurons in Drosophila larvae

Internal sensory neurons monitor the chemical and physical state of the body, providing critical information to the central nervous system for maintaining homeostasis and survival. A population of larval Drosophila sensory neurons, tracheal dendrite (td) neurons, elaborate dendrites along respiratory organs and may serve as a model for elucidating the cellular and molecular basis of chemosensation by internal neurons. We find that td neurons respond to decreases in O2 levels and increases in CO2 levels. We assessed the roles of atypical soluble guanylyl cyclases (Gycs) and a gustatory receptor (Gr) in mediating these responses. We found that Gyc88E/Gyc89Db were necessary for responses to hypoxia, and that Gr28b was necessary for responses to CO2. Targeted expression of Gr28b isoform c in td neurons rescued responses to CO2 in mutant larvae and also induced ectopic sensitivity to CO2 in the td network. Gas-sensitive td neurons were activated when larvae burrowed for a prolonged duration, demonstrating a natural-like feeding condition in which td neurons are activated. Together, our work identifies two gaseous stimuli that are detected by partially overlapping subsets of internal sensory neurons, and establishes roles for Gyc88E/Gyc89Db in the detection of hypoxia, and Gr28b in the detection of CO2.

neuroscience↗

bioRxiv2023

A cell-type-specific nitric oxide-cGMP pathway regulates proprioceptor morphology

Neurons show remarkable morphological diversity facilitated by transcriptional regulation during development and fitting with their connectivity and function. Second messenger pathways mediated by cyclic 3,5 adenosine or guanosine monophosphate (cAMP or cGMP) may serve to integrate extrinsic signals and regulate branching and growth of neurites. We investigated the regulation of cGMP signaling in neuronal morphogenesis in Drosophila somatosensory neurons and found cell type-specificity in expression of the enzyme soluble guanylate cyclase (sGC) in different sensory neuron classes. sGC is responsible for the production of cGMP in response to the diffusible free radical messenger nitric oxide (NO) such that different levels of sGC impart cell type-specific sensitivity to NO. Supporting a role for the NO-cGMP pathway in neuronal morphogenesis, we find that knockout of sGC or nitric oxide synthase (NOS) impacts the morphology of multidendritic proprioceptors. The homeodomain transcription factor Cut shows different levels of expression in different somatosensory neuron types and we find that Cut regulates the level of cGMP signaling via repression of sGC expression. Thus, transcription factor levels contribute to cell type diversification by regulating levels of a signaling pathway to mediate somatosensory neuron morphogenesis.

neuroscience↗

bioRxiv2023

MFN2-dependent recruitment of ATAT1 coordinates mitochondria motility with alpha-tubulin acetylation and is disrupted in CMT2A

Acetylated microtubules play key roles in the regulation of mitochondria dynamics. It has however remained unknown if the machinery controlling mitochondria dynamics functionally interacts with the -tubulin acetylation cycle. Mitofusin-2 (MFN2), a large GTPase residing in the mitochondrial outer membrane and mutated in Charcot-Marie-Tooth type 2 disease (CMT2A), is a regulator of mitochondrial fusion, transport and tethering with the endoplasmic reticulum. The role of MFN2 in regulating mitochondrial transport has however remained elusive. Here we show that mitochondrial contacts with microtubules are sites of -tubulin acetylation, which occurs through the MFN2-mediated recruitment of -tubulin acetyltransferase 1 (ATAT1). We discover that this activity is critical for MFN2-dependent regulation of mitochondria transport, and that axonal degeneration caused by CMT2A MFN2 associated mutations, R94W and T105M, may depend on the inability to release ATAT1 at sites of mitochondrial contacts with microtubules. Our findings reveal a function for mitochondria in regulating acetylated -tubulin and suggest that disruption of the tubulin acetylation cycle play a pathogenic role in the onset of MFN2-dependent CMT2A. O_FIG O_LINKSMALLFIG WIDTH=193 HEIGHT=200 SRC="FIGDIR/small/532838v1_ufig1.gif" ALT="Figure 1"> View larger version (41K): org.highwire.dtl.DTLVardef@3db8eorg.highwire.dtl.DTLVardef@143821corg.highwire.dtl.DTLVardef@1132b13org.highwire.dtl.DTLVardef@1710383_HPS_FORMAT_FIGEXP M_FIG C_FIG HighlightsO_LIMitochondria contacts with MTs are hotspots of -tubulin acetylation through the recruitment of ATAT1 by MFN2 C_LIO_LIMutations in MFN2 associated with CMT2A disease lose this activity by sequestering ATAT1 C_LIO_LIDistal axonal degeneration caused by loss of MFN2 depends on acetylated tubulin-mediated mitochondria transport C_LI eTOCRecruitment of ATAT1 to mitochondria by MFN2 is critical for axonal viability through the regulation of mitochondria transport, and is disrupted in CMT2A

cell biology↗

bioRxiv2023

Regulated alternative splicing of Dscam2 is required for somatosensory circuit wiring

Axon and dendrite placement and connectivity is guided by a wide range of secreted and surface molecules in the developing nervous system. Nevertheless, the extraordinary complexity of connections in the brain requires that this repertoire be further diversified to precisely and uniquely regulate cell-cell interactions. One important mechanism for molecular diversification is alternative splicing. Drosophila Down syndrome cell adhesion molecule (Dscam2) undergoes cell type-specific alternative splicing to produce two isoform-specific homophilic binding proteins. Regulated alternative splicing of Dscam2 is important for dendrite and axon patterning, but how this translates to circuit wiring and animal behavior is not well understood. Here, we examined the role of cell-type specific expression of Dscam2 isoforms in regulating synaptic partner selection in the larval somatosensory system. We found that synaptic partners in the nociceptive circuit express different Dscam2 isoforms. Forcing synaptic partners to express a common isoform resulted in nociceptive axon patterning defects and attenuated nocifensive behaviors, indicating that a role for Dscam2 alternative splicing is to ensure that synaptic partners do not express matching isoforms. These results point to a model in which regulated alternative splicing of Dscam2 across populations of neurons restricts connectivity to specific partners and prevents inappropriate synaptic connections.

neuroscience↗

bioRxiv2023

Neuromuscular Basis of Drosophila larval escape behavior

When threatened by dangerous or harmful stimuli, animals engage in diverse forms of rapid escape behaviors. In Drosophila larvae, one type of escape response involves C-shaped bending and lateral rolling followed by rapid forward crawling. The sensory circuitry that promotes larval escape has been extensively characterized; however, the motor programs underlying rolling are unknown. Here, we characterize the neuromuscular basis of rolling escape behavior. We used high-speed, volumetric, Swept Confocally-Aligned Planar Excitation (SCAPE) microscopy to image muscle activity during larval rolling. Unlike sequential peristaltic muscle contractions that progress from segment to segment during forward and backward crawling, the muscle activity progresses circumferentially during bending and rolling escape behavior. We propose that progression of muscular contraction around the larvas circumference results in a transient misalignment between weight and the ground support forces, which generates a torque that induces stabilizing body rotation. Therefore, successive cycles of slight misalignment followed by reactive aligning rotation lead to continuous rolling motion. Supporting our biomechanical model, we found that disrupting the activity of muscle groups undergoing circumferential contraction progression lead to rolling defects. We use EM connectome data to identify premotor to motor connectivity patterns that could drive rolling behavior, and perform neural silencing approaches to demonstrate the crucial role of a group of glutamatergic premotor neurons in rolling. Our data reveal body-wide muscle activity patterns and putative premotor circuit organization for execution of the rolling escape response. Significance StatementTo escape from dangerous stimuli, animals execute escape behaviors that are fundamentally different from normal locomotion. The rolling escape behavior of Drosophila larvae consists of C-shaped bending and rolling. However, the muscle contraction patterns that lead to rolling are poorly understood. We find that following the initial body bending, muscles contract in a circumferential wave around the larva as they enter the bend, maintaining unidirectional rolling that resembles cylinder rolling on a surface. We study the structure of motor circuits for rolling, inhibit different motor neurons to determine which muscles are essential for rolling, and propose circuit and biomechanical models for roll generation. Our findings provide insights into how motor circuits produce diverse motor behaviors.

neuroscience↗

bioRxiv2020

Scarless engineering of the Drosophila genome near any site-specific integration site

We describe a simple and efficient technique that allows scarless engineering of Drosophila genomic sequences near any landing site containing an inverted attP cassette, such as a MiMIC insertion. This 2-step method combines phiC31 integrase mediated site-specific integration and homing nuclease-mediated resolution of local duplications, efficiently converting the original landing site allele to modified alleles that only have the desired change(s). Dominant markers incorporated into this method allow correct individual flies to be efficiently identified at each step. In principle, single attP sites and FRT sites are also valid landing sites. Given the large and increasing number of landing site lines available in the fly community, this method provides an easy and fast way to efficiently edit the majority of the Drosophila genome in a scarless manner. This technique should also be applicable to other species.

genomics↗

bioRxiv2019

Integrins protect nociceptive neurons in models of paclitaxel-mediated peripheral sensory neuropathy

Chemotherapy induced peripheral neuropathy (CIPN) is a major side effect from cancer treatment with no known method for prevention or cure in clinics. CIPN primarily affects unmyelinated nociceptive sensory terminals. Despite the high prevalence of CIPN, molecular and cellular mechanisms that lead to CIPN are still poorly understood. Here, we used a genetically tractable Drosophila model and primary sensory neurons isolated from adult mouse to examine the mechanisms underlying CIPN and identify protective pathways. We found that chronic treatment of Drosophila larvae with paclitaxel caused sensory neuron degeneration, altered the terminal branching pattern of nociceptive neurons, and reduced thermal nociceptive responses. We found that nociceptive neuron-specific overexpression of integrins, which are known to support neuronal maintenance in several systems, conferred protection from paclitaxel-mediated cellular and behavioral phenotypes. Live imaging and superresolution approaches provide evidence that paclitaxel treatment causes cellular changes that are consistent with alterations in endosome-mediated trafficking of integrins. We used primary dorsal root ganglia neuron cultures to test conservation of integrin-mediated protection. We show that overexpression of a human integrin {beta} subunit 1 (ITGB1) also prevented degeneration following paclitaxel treatment. Altogether, our study supports conserved mechanisms of paclitaxel-induced perturbation of integrin trafficking and a therapeutic potential of restoring integrin levels to antagonize paclitaxel-mediated toxicity in sensory neurons.

neuroscience↗

bioRxiv2018

Characterization of proprioceptive system dynamics in behaving Drosophila larvae using high-speed volumetric microscopy

Proprioceptors provide feedback about body position that is essential for coordinated movement. Proprioceptive sensing of the position of rigid joints has been described in detail in several systems, however it is not known how animals with an elastic skeleton encode their body positions. Understanding how diverse larval body positions are dynamically encoded requires knowledge of proprioceptor activity patterns in vivo during natural movement. Here we applied high-speed volumetric SCAPE microscopy to simultaneously track the position, physical deformation, and temporal patterns of intracellular calcium activity of multidendritic proprioceptors in crawling Drosophila larvae. During the periodic segment contraction and relaxation that occurs during crawling, proprioceptors with diverse morphologies showed sequential onset of activity throughout each periodic episode. A majority of these proprioceptors showed activity during segment contraction with one neuron type activated by segment extension. Different timing of activity of contraction-sensing proprioceptors was related to distinct dendrite terminal targeting, providing a continuum of position encoding during all phases of crawling. These dynamics could endow different proprioceptors with specific roles in monitoring the progression of contraction waves, as well as body shape during other behaviors. We provide activity measurements during exploration as one example. Our results provide powerful new insights into the body-wide neuronal dynamics of the proprioceptive system in crawling Drosophila, and demonstrate the utility of our approach for characterization of neural encoding throughout the nervous system of a freely behaving animal.

neuroscience↗