Biology subjects

Blanchard, M.-P.

Publications and source records attributed to Blanchard, M.-P..

7 recordsLinked to original sources

bioRxiv2026

The Nucleoporin MLP1 of the nuclear basket is essential for nuclear integrity and ploidy maintenance in Trypanosoma brucei

Trypanosoma brucei is a divergent eukaryote parasite responsible for neglected tropical diseases in human and animals, sleeping sickness or human African trypanosomiasis and nagana respectively. Besides scientific interest, understanding the specific features of its biology has medical and economical relevance. Nuclear pore complexes (NPCs) are large multiprotein channels embedded in the nuclear envelope that regulate nucleo-cytoplasmic transport. Beyond this role, NPCs also participate in essential nuclear processes such as chromosome segregation, transcription, and cytokinesis. Here, we showed that Myosin-like protein-1 (MLP1) localized to the nuclear basket of NPCs in T. brucei. Silencing of TbMLP1 by RNA interference in T. brucei procyclic cells caused marked defects in parasite growth, severe impairment of messenger RNA export, disorganization of nuclear structure, and pronounced genomic instability. Flow cytometry and FISH analyses revealed abnormal DNA content and a sharp reduction in disomic cells, accompanied by increased numbers of monosomic, trisomic, and polysomic cells, indicating an untolerated aneuploidy. These findings reveal that TbMLP1 links NPC function to multiple key cellular pathways. We provide new insights into the mechanisms that preserve nuclear architecture, nuclear envelope morphology, genome stability, and faithful chromosome segregation, including effects on kinetochore distribution and organization of the mitotic spindle. Author SummaryTrypanosoma brucei is the microscopic parasite responsible for sleeping sickness in humans and nagana in cattle; learning more about its basic biology may help identify weak points that could one day be targeted in new treatments. In this work, we studied a protein called MLP1, which sits at the nuclear pores--the gateways that control what enters and leaves the nucleus. Our findings revealed that MLP1 is essential for ensuring proper movement of messenger RNA, keeping the nucleus stable, and allowing chromosomes to be shared equally when cells divided. In total, we gained new insight into the basic biology of a parasite that remains a major health concern in many regions of the world, showing how a single structural protein can influence many vital processes within it.

microbiology↗

bioRxiv2025

Deltaviruses spread through a viral Trojan Horse

Hepatitis D-like viral satellites, known as deltaviruses, have been recently discovered in a wide range of animals. These viruses are thought to expropriate glycoproteins from helper viruses to form infectious particles. Here, we challenge this paradigm and demonstrate that deltaviruses are packaged within helper virus particles, using them as viral Trojan Horses for cell entry. By leveraging orthogonal electronic and photonic super-resolution microscopy, we visualize deltaviruses enclosed within virions from rhabdo-, herpes-, and arenavirus families. We show that this conserved hitchhiking mechanism ensures concomitant deltavirus-helper virus spread, which advantages the dissemination of deltaviruses, broadens their host range and expands their tropism. Our findings reveal a previously unrecognized mode of viral transmission, providing a framework to investigate overlooked deltavirus infections outside of the human liver.

microbiology↗

bioRxiv2024

T-type calcium channels participate in intrinsic and synaptic activity of PKCγ neurons of the dorsal horn of the spinal cord during chronic pain

ABSTRACTThe disinhibition of the excitatory PKC{gamma} interneurons plays a central role during mechanical allodynia in the dorsal horn of the spinal cord, routing harmless information to nociceptive pathways. The T-type calcium channel Cav3.2, necessary for mechanical and cold allodynia, is found in most PKC{gamma} neurons of the spinal cord. In this study, the role of Cav3.2 in PKC{gamma} neurons was studied after its pharmacological inhibition and its conditional deletion (KO) in Cav3.2GFP-Flox KI x PKC{gamma}-CreERT2 x Ai14 mice in normal conditions and in the spared-nerve-injury (SNI) model of neuropathic pain. Conditional deletion of Cav3.2 increased the hind-paw basal mechanical sensitivity before surgery, and decreased mechanical pain 7 days, but not 28 days, after surgery. At the cellular level, Cav3.2 participated in the low-threshold currents of PKC{gamma} neurons and the T-type calcium current of PKC{gamma} neurons was decreased in KO mice as compared to wild-type (WT). This loss did not convert into proportional alterations in subthreshold properties including "rebound" potentials, suggesting the involvement of other T-type channels. Action potential kinetics and firing properties seemed similar in WT and KO mice too, but rebound potentials were diminished in the SNI model in WT but not in KO mice. In addition, the modulations of firing properties induced by T-type channel pharmacological blocker Z944 observed in WT mice were absent in KO mice and after SNI. Furthermore, the pairing of action potentials was modified after SNI in WT mice, and not in KO mice. At the synaptic level, excitatory currents were lowered 7- and 28-days after surgery, while inhibitory currents were lowered only at 28 days. These changes were not found in Cav3.2-ablated neurons. Miniature currents analysis indicated that Cav3.2 was involved in both excitatory and inhibitory synaptic transmissions at the level of PKC{gamma} neurons. Surprisingly, Z944 did not mimic the effects of Cav3.2 ablation in PKC{gamma} neurons, suggesting distinct and eventually opposite roles of other T-type calcium channels. Altogether, our results show that Cav3.2 is not mandatory for firing of PKC{gamma} neurons of the dorsal horn of the spinal cord, but that it participates to the SNI-induced changes in their intrinsic and synaptic activity, including changes in their excitatory and inhibitory controls. Graphical abstract O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=147 SRC="FIGDIR/small/627933v1_ufig1.gif" ALT="Figure 1"> View larger version (39K): org.highwire.dtl.DTLVardef@1a297daorg.highwire.dtl.DTLVardef@19f7a76org.highwire.dtl.DTLVardef@120f688org.highwire.dtl.DTLVardef@119658e_HPS_FORMAT_FIGEXP M_FIG C_FIG

neuroscience↗

bioRxiv2024

Septin filament assembly assists the lateral organization of membranes

Compartmentalized interactions of plasma membrane components are essential to support many cell functions, from signaling to cell division, adhesion, migration, or phagocytosis. Cytoskeletal-membrane interactions play an important role in forming membrane compartments, and this feature has been primarily studied through the actin cytoskeleton. Unlike actin, septins directly interact with membranes, acting as scaffolds to recruit proteins to specific cellular locations and as structural diffusion barriers for membrane components. However, how septins interact with and remodel the local membrane environment is unclear. Here we combined minimal reconstituted systems based on fluorescence microscopy and quantitative atomic force microscopy together with live yeast cell imaging and STED microscopy to study septin-mediated membrane organization. Our results show that septins self-assembly into filament-based sub-micrometric patches and high-order structures prompt their membrane-organizing role in vitro and in yeast cells, respectively. Furthermore, we show that the polybasic domain of Cdc11, in addition to the amphipathic helix of Cdc12, plays an essential role in supporting the membrane remodeling and curvature-sensing properties of yeast septins. Collectively, our work provides a framework for understanding the molecular mechanisms by which septins can support cellular functions intimately linked to membranes.

cell biology↗

bioRxiv2021

Epigenetic regulation clocks the multigenerational olfactory imprinting in C. elegans

Imprinting is an early sensory life experience that induces adult behaviours, such as mother recognition or homing. In a previous study, we demonstrated a striking olfactory imprinting in C. elegans that can be inherited over generations. When exposed to specific odorants during a timely controlled post-hatch period, C. elegans worms display during adulthood an enhanced migration towards these molecules. In order to unveil some of the genetic and epigenetic factors that are responsible for such a behavioural plasticity, we assessed the role of heterochronic genes using a candidate gene approach. We report here that translation of the Hunchback-Like 1 (HBL1) transcription factor in the sensory processing interneuron AIY, is a determining factor for olfactory plasticity timing in C.elegans. HBL1 may associate to the SPR1/CoREST co-repressor, the lysine demethylase SPR5/LSD1 and the histone deacetylase HDA3 to lengthen the plasticity period, whereas the translation initiation factor IFE-4 and the histone deacetylase HDA2 abridge it. We also observed that lengthened plasticity periods allow proportionally faster stable behavioral adaptation of C. elegans populations. We conclude that plasticity timing is a key factor, not only to transiently adapt individuals but also to stably adapt animal populations via multigenerational accumulation of experience.

animal behavior and cognition↗

bioRxiv2020

TopBP1 assembles nuclear condensates to switch on ATR signalling.

ATR checkpoint signalling is crucial for cellular responses to DNA replication impediments. Using an optogenetic platform, we show that TopBP1, the main activator of ATR, self-assembles extensively to yield micron-sized condensates. These opto-TopBP1 condensates are functional entities organized in tightly packed clusters of spherical nano-particles. TopBP1 condensates are reversible, occasionally fuse and co-localise with TopBP1 partner proteins. We provide evidence that TopBP1 condensation is a molecular switch that amplifies ATR activity to phosphorylate checkpoint kinase 1 (Chk1) and slowdown replication forks. Single amino acid substitutions of key residues in the intrinsically disordered ATR-activation domain disrupt TopBP1 condensation and, consequently, ATR/Chk1 signalling. In physiologic salt concentration and pH, purified TopBP1 undergoes liquid-liquid phase separation in vitro. We propose that the actuation mechanism of ATR signalling is the assembly of TopBP1 condensates driven by highly regulated multivalent and cooperative interactions.

cell biology↗

bioRxiv2020

A Sequence determinant in 3'UTR of mRNAs for Nuclear Retention by Paraspeckles

Paraspeckles are nuclear membraneless structures composed of a long non-coding RNA, Nuclear-Enriched-Abundant-Transcript-1 and RNA binding proteins, which associate numerous mRNAs. It is therefore believed that their cellular function is to sequester in the nucleus their associated proteins and/or target mRNAs. However, little is known about the molecular determinant in mRNA targets that allow their association to paraspeckles except that inverted repeats of Alu sequences (IRAlu) present in 3UTR of mRNAs may allow this association. While in a previous study we established the list of paraspeckle target RNAs in a rat pituitary cell line, we didnt find however, inverted repeated SINEs, the rat equivalent of primate IRAlus in 3UTR of these RNAs. By developing a candidate gene strategy, we selected a paraspeckle target gene, namely calreticulin mRNA, and we searched for other potential RNA recruitment elements in its 3UTR, since 3UTRs usually contain the sequence recognition for nuclear localization. We found a 15-nucleotide sequence, present as a tandem repeat in 3UTR of this mRNA, which is involved in the nuclear retention by paraspeckles. While being not overrepresented in the 3UTR of the paraspeckle target RNAs, this recruitment element was present in near 30% of all 3UTR mRNAs. In addition, since an oligonucleotide containing this sequence binds the paraspeckle protein component HNRNPK, it is proposed that HNRNPK may constitute a bridging protein between paraspeckles and target mRNAs.

molecular biology↗