Biology subjects

Roussel, J.

Publications and source records attributed to Roussel, J..

7 recordsLinked to original sources

bioRxiv2022

The autism-associated Meis2 gene is necessary for cardiac baroreflex regulation in mice

Recent understanding of Autism Spectrum Disorder (ASD) showed that peripheral primary mechanosensitive neurons involved in touch sensation and central neurons affected in ASD share transcriptional regulators. Mutant mice for ASD-associated transcription factors exhibit impaired primary tactile perception, and restoring those genes specifically in primary sensory neurons rescue some of the anxiety-like behavior and social interaction defects. Interestingly, peripheral mechanosensitive sensory neurons also project to internal organs including the cardio-vascular system, and an imbalance of the cardio-vascular sympatho-vagal regulation is evidenced in ASD and intellectual disability. ASD patients have decreased vagal tone, suggesting dysfunction of sensory neurons involved in cardio-vascular sensing. In light of our previous finding that the ASD-associated Meis2 gene is necessary for normal touch neurons development and function, we investigated here if its inactivation in mouse peripheral sensory neurons also affects cardio-vascular sympatho-vagal regulation and baroreflex. Combining echocardiography, pharmacological challenge, blood pressure monitoring and heart rate variability analysis, we found that Meis2 mutant mice exhibited a blunted vagal response independently of any apparent cardiac malformation. These results suggest that defects in primary sensory neurons with mechanosensitive identity could participate in the imbalanced cardio-vascular sympatho-vagal tone found in ASD patients, reinforcing current hypotheses on the role of primary sensory neurons in the etiology of ASD.

physiology↗

bioRxiv2022

Lateral line hair cells integrate mechanical and chemical cues to orient navigation

The lateral line is a superficial sensory system responding to environmental hydrodynamic changes to orient locomotion of aquatic vertebrate species. Whether this system also detects chemical cues is unknown. We find that zebrafish lateral line hair cells express numerous chemoreceptors, including ionotropic receptors for serotonin. We show that the serotonin enriched in skin neuroepithelial cells is released upon injury and that environmental serotonin activates lateral line hair cells. We show that larval zebrafish exposed to serotonin in their environment rely on the lateral line to swim fast and away. These results uncover the sensory versatility of lateral line hair cells and how these properties modulate navigation in response to environmental stimuli.

neuroscience↗

bioRxiv2021

Spinal sensory neurons project onto hindbrain to stabilize posture and enhance locomotor speed

In the spinal cord, cerebrospinal fluid-contacting neurons (CSF-cNs) are GABAergic interoceptive sensory neurons that detect spinal curvature via a functional coupling with the Reissner fiber. This mechanosensory system has recently been found involved in spine morphogenesis and postural control but the underlying mechanisms are not fully understood. In zebrafish, CSF-cNs project an ascending and ipsilateral axon reaching two to six segments away. Rostralmost CSF-cNs send their axons ipsilaterally into the hindbrain, a brain region containing motor nuclei and reticulospinal neurons (RSNs), which send descending motor commands to spinal circuits. Until now, the synaptic connectivity of CSF-cNs has only been investigated in the spinal cord where they synapse onto motor neurons and premotor excitatory interneurons. The identity of CSF-cN targets in the hindbrain and the behavioral relevance of these sensory projections from spinal cord to hindbrain are unknown. Here, we provide anatomical and molecular evidence that rostralmost CSF-cNs synapse onto the axons of large RSNs including the Mauthner cells and early born chx10+ neurons. Functional anatomy and optogenetic-assisted mapping reveal that rostral CSF-cNs also synapse onto the soma and dendrites of cranial motor neurons innervating hypobranchial muscles. During acousto-vestibular evoked escape responses, ablation of rostralmost CSF-cNs results in a weaker escape response with a decreased C-bend amplitude, lower speed and a deficient postural control. Our study demonstrates that spinal sensory feedback enhances speed and stabilizes posture, and reveals a novel spinal gating mechanism acting on the output of descending commands sent from the hindbrain to the spinal cord. eTOCCerebrospinal fluid-contacting neurons are mechanosensory cells that detect spinal curvature. Wu et al. show here that rostralmost CSF-cNs synapse in the hindbrain onto cranial motor neurons and the descending axons of reticulospinal neurons, and enhance speed and power as well as postural control during active locomotion. HighlightsO_LICerebrospinal fluid-contacting neurons (CSF-cNs) in rostral spinal cord form inhibitory synapses onto cranial motor neurons C_LIO_LIRostral CSF-cNs synapse onto descending axons of reticulospinal neurons C_LIO_LICSF-cN sensory feedback in the rostral spinal cord enhance speed and power of locomotion C_LIO_LIRostral CSF-cNs projecting to the hindbrain contribute to postural control C_LI

neuroscience↗

bioRxiv2020

A lexical approach for identifying behavioral action sequences

Animals display characteristic behavioral patterns when performing a task, such as the spiraling of a soaring bird or the surge-and-cast of a male moth searching for a female. Identifying such recurring sequences occurring rarely in noisy behavioral data is key to understanding the behavioral response to a distributed stimulus in unrestrained animals. Existing models seek to describe the dynamics of behavior or segment individual locomotor episodes rather than to identify the rare and transient sequences of locomotor episodes that make up the behavioral response. To fill this gap, we develop a lexical, hierarchical model of behavior. We designed an unsupervised algorithm called "BASS" to efficiently identify and segment recurring behavioral action sequences transiently occurring in long behavioral recordings. When applied to navigating larval zebrafish, BASS extracts a dictionary of remarkably long, non-Markovian sequences consisting of repeats and mixtures of slow forward and turn bouts. Applied to a novel chemotaxis assay, BASS uncovers chemotactic strategies deployed by zebrafish to avoid aversive cues consisting of sequences of fast large-angle turns and burst swims. In a simulated dataset of soaring gliders climbing thermals, BASS finds the spiraling patterns characteristic of soaring behavior. In both cases, BASS succeeds in identifying rare action sequences in the behavior deployed by freely moving animals. BASS can be easily incorporated into the pipelines of existing behavioral analyses across diverse species, and even more broadly used as a generic algorithm for pattern recognition in low-dimensional sequential data.

animal behavior and cognition↗

bioRxiv2019

Sensory neurons contacting the cerebrospinal fluid require the Reissner fiber to detect spinal curvature in vivo

Recent evidence indicate active roles for the cerebrospinal fluid (CSF) on body axis development and morphogenesis of the spine implying CSF-contacting neurons (CSF-cNs) in the spinal cord. CSF-cNs project a ciliated apical extension into the central canal that is enriched in the channel PKD2L1 and enables the detection of spinal curvature in a directional manner. Dorsolateral CSF-cNs ipsilaterally respond to lateral bending while ventral CSF-cNs respond to longitudinal bending. Historically, the implication of the Reissner fiber (RF), a long extracellular thread in the CSF, to CSF-cN sensory functions has remained a subject of debate. Here, we reveal using electron microscopy in zebrafish larvae that the RF is in close vicinity with cilia and microvilli of ventral and dorsolateral CSF-cNs. We investigate in vivo the role of cilia and the Reissner fiber in the mechanosensory functions of CSF-cNs by combining calcium imaging with patch-clamp recordings. We show that disruption of cilia motility affects CSF-cN sensory responses to passive and active curvature of the spinal cord without affecting the Pkd2l1 channel activity. Since ciliary defects alter the formation of the Reissner fiber, we investigated whether the Reissner fiber contributes to CSF-cN mechanosensitivity in vivo. Using a hypomorphic mutation in the scospondin gene that forbids the aggregation of SCO-spondin into a fiber, we demonstrate in vivo that the Reissner fiber per se is critical for CSF-cN mechanosensory function. Our study uncovers that neurons contacting the cerebrospinal fluid functionally interact with the Reissner fiber to detect spinal curvature in the vertebrate spinal cord. O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=152 SRC="FIGDIR/small/861344v1_ufig1.gif" ALT="Figure 1"> View larger version (42K): org.highwire.dtl.DTLVardef@3c7baaorg.highwire.dtl.DTLVardef@db094forg.highwire.dtl.DTLVardef@4041c6org.highwire.dtl.DTLVardef@9e3dae_HPS_FORMAT_FIGEXP M_FIG C_FIG eToCThe role of the Reissner fiber, a long extracellular thread running in the cerebrospinal fluid (CSF), has been since its discovery in 1860 a subject of debate. Orts-DelImmagine et al. report that the Reissner fiber plays a critical role in the detection of spinal curvature by sensory neurons contacting the CSF. HighlightsO_LISince its discovery, the role of the Reissner fiber has long been a subject of debate C_LIO_LIMechanoreception in CSF-contacting neurons (CSF-cNs) in vivo requires the Reissner fiber C_LIO_LICSF-cN apical extension is in close vicinity of the Reissner fiber C_LIO_LICSF-cNs and the Reissner fiber form in vivo a sensory organ detecting spinal curvature C_LI

neuroscience↗

bioRxiv2018

A tensile ring drives tissue flows to shape the gastrulating amniote embryo

Tissue morphogenesis is driven by local cellular deformations, themselves powered by contractile actomyosin networks. While it is well demonstrated that cell-generated forces at the microscopic scale underlie a variety of local morphogenetic processes (e.g. lengthening/ narrowing1-4, bending5-8, or folding9,10), how such local forces are transmitted across tissues to shape them at a mesoscopic scale remains largely unknown. Here, by performing a quantitative analysis of gastrulation in entire avian embryos, we show that the formation of the primitive streak and the associated large-scale rotational tissue flows (i.e. polonaise movements11,12) are integral parts of a global process that is captured by the laws of fluid mechanics. We identify a large-scale supracellular actomyosin ring (2 mm in diameter and 250 m thick) that shapes the embryo by exerting a graded tension along the margin between the embryonic and extra-embryonic territories. Tissue-wide flows arise from the transmission of these localized forces across the embryonic disk and are quantitatively recapitulated by a fluid-mechanical model based on the Stokes equations for viscous flow. We further show that cell division, the main driver of cell rearrangements at this stage13, is required for fluid-like behavior and for the progress of gastrulation movements. Our results demonstrate the power of a hydrodynamic approach to tissue-wide morphogenetic processes14-16 and provide a simple, unified mechanical picture of amniote gastrulation. A tensile embryo margin, in addition to directing tissue motion, could act as an interface between mechanical and molecular cues, and play a central role in embryonic self-organization.

developmental biology↗

bioRxiv2018

Timed collinear activation of Hox genes during gastrulation controls the avian forelimb position

Limb position along the body is highly consistent within one species but very variable among vertebrates. Despite major advances in our understanding of limb patterning in three dimensions, how limbs reproducibly form along the anteroposterior axis remains largely unknown. Hox genes have long been suspected to control limb position, however supporting evidences are mostly correlative and their role in this process remains unclear. Here we show that Hox genes determine the avian forelimb position in a two-step process: first, their sequential collinear activation during gastrulation controls the relative position of their own successive expression domains along the body axis. Then, within these collinear domains, Hox genes differentially activate or repress the genetic cascade responsible for forelimb initiation. Furthermore, we provide evidences that changes in the timing of collinear Hox gene activation might underlie natural variation in forelimb position between different birds. Altogether our results which characterize the cellular and molecular mechanisms underlying the regulation and natural variation of forelimb position in avians, show a direct and early role for Hox genes in this process.

developmental biology↗