Biology subjects

Bonnet, C.

Publications and source records attributed to Bonnet, C..

11 recordsLinked to original sources

bioRxiv2025

Mitotic single-stranded DNA suppression by DDIAS

Incomplete DNA replication and chromosome breakage during mitosis pose major threats to chromosome segregation. The CIP2A-TOPBP1 complex acts to mitigate this peril, but its exact role is not yet understood. Here, we report that DDIAS acts as a DNA-binding effector of the CIP2A-TOPBP1 complex. DDIAS directly interacts with TOPBP1 and the disruption of this interaction or inactivation of its single-stranded DNA (ssDNA)-binding ability impairs genome integrity and causes synthetic lethality with BRCA1 and BRCA2 deficiency. DDIAS does not promote the putative end-tethering function of CIP2A-TOPBP1 but rather acts to suppress ssDNA during mitosis. This role is emphasized by a pronounced genetic interaction between the genes coding for DDIAS and DNA polymerase (. We conclude that DDIAS defines a mitotic DNA damage response that mitigates the threat of mitotic ssDNA arising from DNA replication stress, which we infer is a liability to accurate chromosome segregation. (144 words).

molecular biology↗

bioRxiv2025

WEE1 inhibitors trigger GCN2-mediated activation of the integrated stress response

The WEE1 kinase negatively regulates CDK1/2 to control DNA replication and mitotic entry. Genetic factors that determine sensitivity to WEE1 inhibitors (WEE1i) are largely unknown. A genome-wide insertional mutagenesis screen revealed that mutation of EIF2A, a translation regulator, sensitized to WEE1i. Mechanistically, WEE1i treatment triggers a translational shut-down, which is lethal in combination with the reduced translation of EIF2AKO cells. A genome-wide CRISPR-Cas9 screen revealed that inactivation of integrated stress response (ISR) kinases GCN1/2 rescued WEE1i-mediated cytotoxicity. WEE1i induced GCN2 activation, ATF4 upregulation, and altered ribosome dynamics. Loss of the collided ribosome sensor ZNF598 conversely increased sensitivity to WEE1i. Notably, the ISR was not required for WEE1i to induce DNA damage, premature mitotic entry or sensitization to DNA-damaging chemotherapeutics. ISR activation was independent of CDK1/2 activation. Importantly, WEE1i-mediated ISR activation was independent of WEE1 presence, pointing at off-target effects, which are shared by multiple chemically distinct WEE1i. This response was also observed in peripheral blood mononuclear cells. Importantly, low-dose WEE1 inhibition did not induce ISR activation, while it still synergized with PKMYT1 inhibition. Taken together, WEE1i triggers toxic ISR activation and translational shutdown, which can be prevented by low-dose or combination treatments, while retaining the cell cycle checkpoint-perturbing effects.

cancer biology↗

bioRxiv2024

Predictive posture stabilization before contact with moving objects: equivalence of smooth pursuit tracking and peripheral vision

Postural stabilization is essential to effectively interact with our environment. Humans preemptively adjust their posture to counteract impending disturbances, such as those encountered during interactions with moving objects, a phenomenon known as anticipatory postural adjustments (APAs). APAs are thought to be influenced by predictive models that incorporate object motion via retinal motion and extra-retinal signals. Building on our previous work that examined APAs in relation to the perceived momentum of moving objects, here we explored the impact of object motion within different visual field sectors on the human capacity to anticipate motion and prepare APAs for contact between virtual moving objects and the limb. Participants interacted with objects moving towards them under different gaze conditions. In one condition, participants fixated on either a central point (central fixation) or left-right of the moving object (peripheral fixation), while in another, they followed the moving object with smooth pursuit eye movements (SPEM). We found that APAs had the smallest magnitude in the central fixation condition and that no notable differences in APAs were apparent between the SPEM and peripheral fixation conditions. This suggests that the visual system can accurately perceive motion of objects in peripheral vision for posture stabilization. Using Bayesian Model Averaging, we also evaluated the contribution of different gaze variables, such as eye velocity and gain (ratio of eye and object velocity) and showed that both eye velocity and gain signals were significant predictors of APAs. Taken together, our study underscores the roles of oculomotor signals in modulation of APAs. New and NoteworthyWe show that the human visuomotor system can detect motion in peripheral vision and make anticipatory adjustments to posture before contact with moving objects, just as effectively as when the eye movement system tracks those objects through smooth pursuit eye movements. These findings pave the way for research into how age-induced changes in spatial vision, eye movements, and motion perception could affect the control of limb movements and postural stability during motion-mediated interactions with objects.

neuroscience↗

bioRxiv2024

Short-term performance impairment in adaptive reaching following exercise induced neuromuscular fatigue in lower-limb postural muscles

Neuromuscular fatigue (NMF) induces temporary reductions in muscle force production capacity, affecting various aspects of motor function. While studies have extensively explored NMFs impact on muscle activation patterns and postural stability, its influence on motor adaptation processes remains less understood. This paper investigates the effects of localized NMF on motor adaptation during upright stance, focusing on reaching tasks. Utilizing a force field perturbation paradigm, participants performed reaching movements while standing upright before and after inducing NMF in the ankle dorsiflexor muscles. Results revealed that despite maintained postural stability, participants in the NMF group exhibited larger movement errors during reaching tasks, suggesting impaired motor adaptation. This was evident in both initial and terminal phases of adaptation, indicating a disruption in learning processes rather than a decreased adaptation rate. Analysis of electromyography activation patterns highlighted distinct strategies between groups, with the NMF group showing altered activation of both fatigued and non-fatigued muscles. Additionally, differences in co-activation patterns suggested compensatory mechanisms to prioritize postural stability despite NMF-induced disruptions. These findings underscore the complex interplay between NMF, motor adaptation, and postural control, suggesting a potential role for central nervous system mechanisms in mediating adaptation processes. Understanding these mechanisms has implications for sports performance, rehabilitation, and motor skill acquisition, where NMF may impact the learning and retention of motor tasks. Further research is warranted to elucidate the transient or long-term effects of NMF on motor adaptation and its implications for motor rehabilitation interventions. New & NoteworthyWe assessed motor adaptation during force field reaching following exercise-induced neuromuscular fatigue (NMF) on postural muscles. NMF impaired adaptation in performance. Similarly, diverging activation strategies were observed in the muscles. No effects were seen on measures of postural control. These results suggest the remodulation of motor commands to the muscles in presence of NMF, which may be relevant in settings where participants could be exposed to NMF while learning, such as sports and rehabilitation.

physiology↗

bioRxiv2023

53BP1 interacts with the RNA primer from Okazaki fragments to support their processing during unperturbed DNA replication

RNA-binding proteins are found at replication forks, but their direct interaction with DNA-embedded RNA species that inevitably shape physiological DNA replication remains unexplored. Here we report that 53BP1, involved in the DNA damage and replication stress response, is an RNA-binding protein that directly interacts with Okazaki fragments, in the absence of any external stress. The bulk chromatin association of 53BP1 shows dramatic dependence on PRIM1, which synthesizes the RNA primer of Okazaki fragments. The direct recruitment of 53BP1 to nascent DNA shows susceptibility to in situ ribonuclease A treatment. Conversely, depletion of FEN1, which results in the accumulation of uncleaved RNA primers, leads to an upregulation of 53BP1 levels at the replication forks, suggesting that RNA primers contribute to the recruitment of 53BP1 at the lagging DNA strand. 53BP1 depletion induces an accumulation of S phase poly(ADP-ribose), which constitutes a sensor of unligated Okazaki fragments. Collectively, our data indicate that 53BP1, distinct from its canonical mode of chromatin-binding, is anchored at the replication fork through its RNA-binding activity, highlighting the role of an RNA-protein interaction at DNA replication forks.

molecular biology↗

bioRxiv2023

A common flanking variant is associated with enhanced meiotic stability of the FGF14-SCA27B locus

The factors driving initiation of pathological expansion of tandem repeats remain largely unknown. Here, we assessed the FGF14-SCA27B (GAA)*(TTC) repeat locus in 2,530 individuals by long-read and Sanger sequencing and identified a 5-flanking 17-bp deletion-insertion in 70.34% of alleles (3,463/4,923). This common sequence variation was present nearly exclusively on alleles with fewer than 30 GAA-pure repeats and was associated with enhanced meiotic stability of the repeat locus.

genetics↗

bioRxiv2022

4.1N and SAP97 regulate different phases of AMPA receptor intracellular transport

Changes in the number of synaptic AMPA subtypes of glutamate receptors (AMPAR) underlie many forms of synaptic plasticity. These variations are controlled by a complex interplay between their intracellular transport (IT), export to the plasma membrane, stabilization at synaptic sites, and recycling. The differential molecular mechanisms involved in these various trafficking pathways and their regulation remains partly unknown. We have recently reported the visualization of AMPAR IT in cultured hippocampal neurons and demonstrated its regulation during synaptic plasticity inducing protocols (Hangen, Cordelieres et al., 2018), opening the path to the differential analysis of the mechanisms controlling AMPAR transport and exocytosis. The cytosolic C-terminal (C-ter.) domain of AMPAR GluA1 subunit is specifically associated with cytoplasmic proteins that could be implicated in the regulation of their IT such as 4.1N and SAP97. Here we analyze how interactions between GluA1 and 4.1N or SAP97 regulate IT and exocytosis at the plasma membrane in basal condition and after cLTP induction. We use sh-RNA against 4.1N and SAP97 and specific mutations and deletions of GluA1 C-ter. domain to characterize how these interactions are involved in coupling AMPAR to the transport machinery. The down-regulation of both 4.1N or SAP97 by shRNAs decrease GluA1 containing vesicle number, modify their transport properties and decrease GluA1 export to the PM, indicating their role in GluA1 IT. The total deletion of the C-ter. domain of GluA1 fully suppresses its IT. Disruption of GluA1 binding to 4.1N decreases the number of GluA1 containing transport vesicles, inhibits GluA1 externalization but does not affect the transport properties of the remaining GluA1 containing vesicles. This indicates a role of the 4.1N-GluA1 interaction during exocytosis of the receptor in basal transmission. In contrast, disrupting the binding between SAP97 and GluA1 modifies the basal transport properties of GluA1 containing vesicles and decreases GluA1 export to the plasma membrane. Importantly, disrupting GluA1 interaction with either 4.1N or SAP97 prevents both the cLTP induced increase in the number of GluA1 containing vesicles observed in control and GluA1 externalization. Our results demonstrate that specific interactions between 4.1N or SAP97 with GluA1 have different roles in GluA1 IT and exocytosis. During basal transmission, the binding of 4.1N to GluA1 allows the fusion/fission membrane exocytosis whereas the interaction with SAP97 is essential for GluA1 IT. During cLTP the interaction of 4.1N with GluA1 allows both IT and exocytosis of the receptor in hippocampal cultured neurons. Altogether, our results identify the differential roles of 4.1N and SAP97 in the control of various phases of GluA1 IT.

neuroscience↗

bioRxiv2022

Enhanced cognitive interference during visuomotor tasks may cause eye-hand dyscoordination

In complex visuomotor tasks, such as cooking, people make many saccades to continuously search for items before and during reaching movements. These tasks require use of short-term memory and task-switching (e.g., switching search between vegetables and spices). Cognitive load may affect visuomotor performance by increasing the demands on mental processes mediated by the prefrontal cortex, but mechanisms remain unclear. It is also unclear how patients with neurological injuries, e.g., stroke survivors, manage greater cognitive loads during visuomotor tasks. Using the Trail-Making Test, we have previously shown that stroke survivors make many more saccades, which are associated limb movements that are less smooth and slower. In this test, participants search for and make reaching movements towards twenty-five numbers and letters. It has a simple variant (Trails-A), and a cognitively challenging variant (Trails-B) that requires alphanumeric switching. The switching makes the task gradually harder as the Trails-B trial progresses (greater cognitive load). Here, we show that stroke survivors and healthy controls made many more saccades and had longer fixations as the Trails-B trial progressed. In addition, reaching speed slowed down for controls in Trails-B. We propose a mechanism where enhanced cognitive load may reduce inhibition from the prefrontal cortex and disinhibit the ocular motor system into making more saccades. These additional saccades may subsequently slow down motor function by disrupting the visual feedback loops used to control limb movements. These findings augment our understanding of the mechanisms that underpin cognitive interference dynamics when visual, ocular, and limb motor systems interact in visuocognitive motor tasks. NEW & Noteworthyo We used a neuropsychological test called the Trails-Making-test and analyze patterns of eye and reaching movements in controls and stroke survivors. We characterized how gaze and reaching movements change within a trial in the easier Trails-A and the more cognitively challenging Trails-B variant that requires alphanumeric switching. We found that as the Trails-B trial progressed participants made more saccadic eye movements and longer fixations, likely because of greater cognitive load.

neuroscience↗

bioRxiv2022

The tetraspanin TSPAN5 regulates AMPARs exocytosis by interacting with the AP-4 complex

Intracellular trafficking of AMPA receptors is a tightly regulated process which involves several adaptor proteins, and is crucial for the activity of excitatory synapses in both basal conditions and during synaptic plasticity. We found that, in rat hippocampal neurons, an intracellular pool of the tetraspanin TSPAN5 specifically promotes exocytosis of newly synthesised GluA2-containing AMPA receptors without affecting their internalisation. TSPAN5 mediates this function by interacting with AP-4 and Stargazin and possibly using recycling endosomes as a delivery route. This work highlights TSPAN5 as a new adaptor regulating AMPA receptor trafficking. In addition, it provides a possible mechanism for the intellectual disability symptoms that occur in AP-4 deficiency syndrome.

neuroscience↗

bioRxiv2021

Interspecific interactions regulate plant reproductive allometry in cereal-legume intercropping systems

O_LICalls for ecological principles in agriculture have gained momentum. Intercropping systems have long been designed by growing two, or more, annual crop species in the same field, aiming for a better resource use efficiency. However, assembly rules for their design are lacking. Notably, it is still unknown whether species performances are maximized during both the vegetative and reproductive phases given the sensitivity of reproductive allocation rules to resource limitation. Interestingly, ecological theory provides expectations regarding putative invariance of plant reproductive allometry (PRA) under non-limiting conditions for plant growth. Here we examined whether and how PRA changes in response to plant-plant interactions in intercropping systems, which can inform both ecological theory and the understanding of the functioning of intercropping systems. C_LIO_LIWe analyzed a dataset of 28 field cereal-legume intercropping trials from various climatic and management conditions across Western Europe. PRA was quantified in both mixing and single-species situations. C_LIO_LIPRA was positively impacted in specific management conditions, leading to a greater increase in yield for a given increase in plant size. Variations in PRA were more beneficial for legumes grown in unfertilized mixture, which explains their use as a key component in actual intercrop systems. The response for cereals was similar but less pronounced in magnitude, and was greater under limiting resource conditions. Focusing on intercropping conditions, hierarchical competition (indicated by biomass difference between intercropped species) appears as a strong driver of the reproductive output of a given species. C_LIO_LISynthesis and applications. Plant reproductive allometry behaves in crop species in the same way as it does in wild species. However, contrary to theoretical expectations about an overall invariance of PRA, we highlighted taxon-specific and context-dependent effects of plant-plant interactions on PRA. This systematic deviation to PRA expectations could be leveraged to cultivate each species up to its reproductive optimum while accounting for the performance of the other, whether farmers objective is to favor one species or to reach an equilibrium in seed production. Sowing density and cultivar choice could regulate the biomass of each component, with specific targets derived from allometric relationships, aiming for an optimal reproductive allocation in mixtures. C_LI

ecology↗

bioRxiv2020

BARD1 links histone H2A Lysine-15 ubiquitination to initiation of BRCA1-dependent homologous recombination

Protein ubiquitination at sites of DNA double-strand breaks (DSBs) by RNF168 recruits BRCA1 and 53BP1, mediators of the homologous recombination (HR) and non-homologous end joining (NHEJ) DSB repair pathways, respectively. While NHEJ relies on 53BP1 binding to ubiquitinated Lysine 15 on H2A-type histones (H2AK15ub), an RNF168-dependent modification, the mechanism linking RNF168 to BRCA1 recruitment during HR has remained unclear. Here, we identify a tandem BRCT domain ubiquitin-dependent recruitment motif (BUDR) in BARD1 - BRCA1s obligate partner protein - that binds H2AK15ub directly, thereby recruiting BRCA1 to DSBs. BARD1 BUDR mutations compromise HR, and render cells hypersensitive to PARP inhibition and cisplatin treatment. We find that BARD1-nucleosome interactions require BUDR binding to H2AK15ub and ankyrin repeat domain-mediated binding of the histone H4 tail, specifically when unmethylated on Lysine-20 (H4K20me0), a state limited to post replicative chromatin. Finally, we demonstrate that by integrating DNA damagedependent H2AK15ub and DNA replication-dependent H4K20me0 signals at sites of DNA damage, BARD1 coordinates BRCA1-dependent HR with 53BP1 pathway antagonization, establishing a simple paradigm for the governance of DSB repair pathway choice.

molecular biology↗