Biology subjects

Desban, L.

Publications and source records attributed to Desban, L..

6 recordsLinked to original sources

bioRxiv2026

Serotonergic Control of Spine Morphology During Growth in Zebrafish

Scoliosis is a three-dimensional deformity of the vertebral column that commonly emerges during growth, yet the biological mechanisms that initiate and drive curve progression remain poorly understood. Serotonin (5-hydroxytryptamine [5-HT]) has long been linked to scoliosis through its relationship with pineal melatonin signaling and through genetic associations with human disease, but its role in spinal morphogenesis has remained unclear. Here, using zebrafish, we show that serotonergic signaling is required for normal spine morphology. Transient exposure to 5-HT during development induces later spinal abnormalities, while loss of Tph2, the principal enzyme required for neuronal 5-HT synthesis, causes progressive three-dimensional spinal curvature during juvenile growth, mimicking aspects of adolescent idiopathic scoliosis (AIS). tph2 mutants undergo initially normal vertebral patterning while targeted ablation of the pineal gland does not induce scoliosis, arguing against a pineal or early skeletal origin for the 5-HT-associated spinal curves. The Reissner fiber, which has been linked to spinal curvature in zebrafish, also formed normally in tph2 mutants. Instead, mutants showed a marked reduction in Fev-expressing intraspinal serotonergic neurons together with increased locomotor activity. Mutants exhibited longer swim bouts and shorter periods of inactivity between bouts. Importantly, these motor defects were evident shortly before the onset of overt spinal curvature. Together, these findings identify neuronal serotonin as a critical regulator of spinal stability and support a model in which altered serotonergic control of motor function changes the mechanical environment experienced by the growing spine, increasing its susceptibility to progressive curvature.

developmental biology↗

bioRxiv2026

Social modulation of activity and orientation fosters complex interactions in young zebrafish

Zebrafish are an important model organism for investigating collective behavior and neuropsychiatric disorders due to attributes such as fast development, high genetic homology with humans and a rich behavioral repertoire. Social behavior in zebrafish emerges as early as twelve days post-fertilization, building toward diverse, coordinated, and complex adult interactions. Most studies on social phenotypes, including in zebrafish, have focused on adult animals and assess isolated traits such as aggression, boldness, or social memory, leaving the critical period of early development when sociality emerges and the mechanisms underlying social behavior establishment largely unexplored. We present here a behavior analysis pipeline that identifies features describing general locomotion and social behavior based on simple geometric criteria. We apply this analysis to pairs of freely interacting two-week-old zebrafish and characterize nascent social preference. We find that young zebrafish favor a specific range of inter-fish distances, creating a social space characterized by specific modulation of locomotion features. Through quantitative analysis and modeling, we show that this proximity behavior is largely established through a turning bias toward counterparts and a socially induced suppression of the variance in turning angles over broader ranges of inter-fish distances. Furthermore, we describe how proximity fosters engagement by young zebrafish in transient, complex short-range physical interactions that include various forms of inter-fish contacts, reminiscent of patterns described in adult animals. Our approach has broad applications for understanding the ontogeny of sociality and collective behaviors and describing subtle phenotypes associated with various human disorders.

animal behavior and cognition↗

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↗

bioRxiv2022

A mucin-regulated adhesin determines the intestinal biogeography and inflammatory character of a bacterial symbiont.

In a healthy gut, microbes are often aggregated with host mucus, yet the molecular basis for this organization and its impact on intestinal health are unclear. Mucus is a viscous physical barrier separating resident microbes from epithelia, but also provides glycan cues that regulate microbial behaviors. Using experimental evolution, we discovered a mucin-sensing pathway in an Aeromonas symbiont of zebrafish, Aer01. In response to the mucin-associated glycan N-acetylglucosamine, a sensor kinase regulates expression of a mucin-binding adhesin we named MbpA. When MbpA is disrupted, Aer01 colonizes to normal levels, but is largely planktonic and elicits increased intestinal inflammation, traits which are reversed by increasing cell surface MpbA. MbpA-like adhesins are common in human-associated bacteria and expression of an Akkermansia muciniphila MbpA-like adhesin in MbpA-deficient Aer01 restored lumenal aggregation and reversed its pro-inflammatory character. Our work demonstrates how resident bacteria use mucin glycans to modulate behaviors congruent with host health.

microbiology↗

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

Simultaneous fluorescence imaging of tilted focal planes at two depths in thick neural tissue: Implementation with remote focus in a widefield electrophysiological microscope.

Wide-field imaging conventionally results in a single image plane oriented perpendicular to the optical axis. However, in brain slice or in vivo recording, neuronal or circuit morphologies lie in arbitrarily tilted planes. Consequently the spatiotemporal advantages of wide-field non-scanned imaging are lost because of the time required for stepwise focal readjustments to view an entire neuron or network. We describe an application of remote focus that views simultaneously two planes separated by up to 100 {micro}m, each with variable tilt from the conventional image plane. This permits fluorescence detection of ion fluxes or membrane potential across neuronal compartments and their correlation with electrical activity. Further, two fluorophores can be viewed simultaneously in each plane. We show (i) neuronal images tilted to optimise simultaneous aquisition of somatic, dendritic and axonal compartments; (ii) networks viewed simultaneously at 2 depths separated by up to 100 {micro}m, (iii) widefield imaging at 30 Hz of Gcamp5 fluorescence during spontaneous spiking in motoneuron layers of zebrafish spinal cord separated by 30-40 microns.

neuroscience↗