Biology subjects

Dumoulin, A.

Publications and source records attributed to Dumoulin, A..

6 recordsLinked to original sources

bioRxiv2026

Secretion of small extracellular vesicles is required for commissural axon guidance at a choice point

The formation of neural circuits relies on precise axonal pathfinding mediated by guidance molecules and their receptors. While the expression of specific guidance molecules by different cell types in the nervous system is well characterized, the mechanisms underlying their secretion and delivery to growing axons remain relatively unexplored. Small extracellular vesicles (sEVs), including exosomes, have emerged as candidate mediators of intercellular communication during nervous system development, with reported roles in neuronal differentiation, synaptogenesis, and axonal outgrowth/regeneration. Whether sEV secretion contributes to axon guidance remains unknown. Here, we show that axons of dorsal interneurons depend on sEV secretion from floor-plate cells to navigate their intermediate target, the floor plate of the developing chicken spinal cord. Blocking biogenesis of exosomes, a subtype of sEVs, via silencing Rab27a either pharmacologically ex vivo or genetically in vivo, impairs axon guidance at the floor plate, mainly by interfering with post-crossing navigation. These findings are reproduced after blocking CD63-positive sEV secretion by preventing their formation in multivesicular bodies due to inhibition of VPS4A function. In both cases, axon guidance at the floor plate is perturbed, as axons fail to turn rostral after midline crossing. Taken together, our results show that sEV secretion is required for guidance decisions at a choice point.

neuroscience↗

bioRxiv2022

Probabilistic axon targeting dynamics lead to individualized brain wiring

Developmental variation in brain-wiring contributes to behavioural individuality1,2. However, how and when individualized wiring diagrams emerge and become stable during development remains largely unknown. Here, we explored axon targeting dynamics in individual brains using live-imaging of a developing Drosophila visual circuit and discovered that targeting choice is an algorithmic multi-step growth process with variable outcomes. Using optogenetics, we found that temporally restricted Notch lateral-inhibition defines a subset of neurons with a probabilistic potential to innervate distal targets. Next, axons from NotchOFF neurons amplify into long actin-rich multi-fibre structures necessary for distal growth. A subset of these NotchOFF neurons create distal targeting axons by stabilizing microtubule growth in one of their actin fibres. Amplified axons without tubulin-stabilized fibres retract, resulting in the stochastic selection of a different number of distal targeting axons in each brain. Pharmacological microtubule destabilization suffices to inhibit this targeting. We observed a similar axonal amplification-stabilization process in the developing chick spinal cord, suggesting a conserved mechanism. Finally, early microtubule patterns predict the adult brain-wiring of an individual in a target-independent manner prior to synapse formation3,4. Thus, we show that a temporal succession of genetically encoded stochastic processes explains the emergence of individual wiring variation. One-Sentence SummaryThe temporal succession of stochastic developmental processes explains the emergence of individual wiring variation.

neuroscience↗

bioRxiv2022

A cell-autonomous role for primary cilia in long-range commissural axon guidance

Ciliopathies are characterized by the absence or dysfunction of primary cilia. Despite the fact that cognitive impairments are a common feature of ciliopathies, how cilia dysfunction affects neuronal development has not been characterized in detail. Here, we show that the primary cilium is required cell-autonomously by neurons during neural circuit formation. In particular, the primary cilium is crucial during axonal pathfinding for the switch in responsiveness of axons at a choice point, or intermediate target. Utilizing animal models and in vivo, ex vivo, as well as in vitro experiments, we provide evidence for a critical role of the primary cilium in long-range axon guidance. The primary cilium on the cell body of commissural neurons transduces long-range guidance signals sensed by growth cones navigating an intermediate target. In extension of our finding that Shh is required for the rostral turn of post-crossing commissural axons, we show here that the cilium is required for a transcriptional change of axon guidance receptors, which in turn mediate the repulsive response to floorplate-derived Shh shown by post-crossing commissural axons.

neuroscience↗

bioRxiv2021

Identification of a stereotypic molecular arrangement of glycine receptors at native spinal cord synapses

Precise quantitative information about the molecular architecture of synapses is essential to understanding the functional specificity and downstream signaling processes at specific populations of synapses. Glycine receptors (GlyRs) are the primary fast inhibitory neurotransmitter receptors in the spinal cord and brainstem. These inhibitory glycinergic networks crucially regulate motor and sensory processes. Thus far the nanoscale organization of GlyRs underlying the different network specificities has not been defined. Here, we have quantitatively characterized the molecular arrangement and ultra-structure of glycinergic synapses in spinal cord tissue using quantitative super-resolution correlative light and electron microscopy (SR-CLEM). We show that endogenous GlyRs exhibit equal receptor-scaffold occupancy and constant packing densities of about 2000 GlyRs m-2 at synapses across the spinal cord and throughout adulthood, even though ventral horn synapses have twice the total copy numbers, larger postsynaptic domains and more convoluted morphologies than dorsal horn synapses. We demonstrate that this stereotypic molecular arrangement is maintained at glycinergic synapses in the oscillator mouse model of the neuromotor disease hyperekplexia despite a decrease in synapse size, indicating that the molecular organization of GlyRs is preserved in this hypomorph. We thus conclude that the morphology and size of inhibitory postsynaptic specializations rather than differences in GlyR packing determine the postsynaptic strength of glycinergic neurotransmission in motor and sensory spinal cord networks.

molecular biology↗

bioRxiv2020

Axon guidance at the midline - a live imaging perspective

During neural circuit formation, axons navigate several choice points to reach their final target. At each one of these intermediate targets, growth cones need to switch responsiveness from attraction to repulsion in order to move on. Molecular mechanisms that allow for the precise timing of surface expression of a new set of receptors that support the switch in responsiveness are difficult to study in vivo. Mostly, mechanisms are inferred from the observation of snapshots of many different growth cones analyzed in different preparations of tissue harvested at distinct time points. However, to really understand the behavior of growth cones at choice points, a single growth cone should be followed arriving at and leaving the intermediate target. Here, we describe a spinal cord preparation that allows for live imaging of individual axons during navigation in their intact environment. The possibility to observe single growth cones navigating their intermediate target allows for measuring growth speed, changes in morphology, or aberrant behavior. Moreover, observation of the intermediate target - the floor plate - revealed its active participation and interaction with commissural axons during midline crossing. Summary statementLive tracking of single growth cones is more informative about axonal behavior during navigation than inference of behavior from the analyses of snapshots of different growth cones.

neuroscience↗

bioRxiv2019

SUSD4 Controls Activity-Dependent Degradation of AMPA Receptor GLUA2 and Synaptic Plasticity

Fine control of protein stoichiometry at synapses underlies brain function and plasticity. How proteostasis is controlled independently for each type of synaptic protein in a synapse-specific and activity-dependent manner remains unclear. Here we show that SUSD4, a complement-related transmembrane protein, binds the AMPA receptor subunit GLUA2 and controls its activity-dependent degradation. Several proteins with known roles in the regulation of AMPA receptor turnover, in particular ubiquitin ligases of the NEDD4 subfamily, are identified as SUSD4 binding partners. SUSD4 is expressed by many neuronal populations starting at the time of synapse formation. Loss-of-function of Susd4 in the mouse prevents long-term depression at cerebellar synapses, and leads to impairment in motor coordination adaptation and learning. Our findings reveal that activity-dependent synaptic plasticity relies on a transmembrane CCP domain-containing protein that regulates the degradation of specific substrates. This mechanism potentially accounts for the role of SUSD4 mutations in neurodevelopmental diseases.

neuroscience↗