Biology subjects

Raineteau, O.

Publications and source records attributed to Raineteau, O..

10 recordsLinked to original sources

bioRxiv2026

Selective vulnerability of intracortical projection neurons drives long-term cortical circuit rewiring after perinatal hypoxia

Cortical circuits are built at perinatal times and gradually refined in an activity-dependent manner during a so-called postnatal period of critical plasticity. Although lesions of the central nervous system (CNS) happening during this period typically recover better than those occurring later in life, they are often associated with long-term behavioral deficits. This suggests that neuronal circuits rewiring, in particular within the cortex, may either be incomplete or inappropriate. To address this possibility, we used chronic perinatal hypoxia, a mouse model of very premature birth. We confirmed that chronic hypoxia induced a decrease in cortical thickness frequently observed in very preterm babies, which rapidly recovered 8 days later. To explore the transcriptional correlates of this recovery we next performed single-nuclei transcriptomic analysis of the cortex at short (P11) and long (P45) timepoints following hypoxia. This revealed persistent transcriptional changes within neurons, including of genes involved in mitochondrial metabolism, axonogenesis and synaptogenesis. Further, histological analysis using anterograde and retrograde tracing as well as mitochondrial labelling support persistent alterations in upper cortical neurons resulting in increased cortico-cortical connectivity within the cortex of adult hypoxic mice. Finally, behavioral testing revealed altered social behavior in mice exposed to chronic hypoxia, which amplified with age. Altogether, our results unravel how brain lesions happening early in life, alter normal cortical development and have long term consequences on cortical wiring, contributing to the observed behaviors defects appearing later in life.

neuroscience↗

bioRxiv2024

Comparative study of pre- and post-mortem perfusion of fixative for the quality of neuronal tissue preparation

Transcardiac perfusion of fixative agent is generally recommended for quality preparations for cerebral histology, ensuring rapid and deep penetration in the tissue to preserve the most fragile brain structures. Despite being performed under anesthesia and with proper analgesia, this procedure is cumbersome for the experimenter and raises ethical questions. Recently, alternative protocols have been proposed, based on prior sacrifice of the animal followed by an injection of a fixative agent into the circulation. These so-called post-mortem perfusion protocols should in theory ensure an equivalent quality of tissue fixation, without exposing live animals to a procedure. Before adopting this new method, it is necessary to validate that sample quality is equivalent, ensuring the validity of scientific results. We performed a parallel comparison of several protocols of tissue fixation, by transcardiac or post-mortem perfusion, and measured the impact on the maintenance of axonal structures, dendritic spines, and mitochondrial morphology. Our results showed that histological parameters show variable sensitivity to perfusion condition and fixative used. For instance, axon fragmentation and altered mitochondrial morphology were observed in post-mortem perfusion groups. We furthermore determined that fixation condition had a variable effect on immunostaining, impacting detected expression level or pattern. Our results serve as a guide to orient the experimenter in selecting the best condition for optimal tissue fixation, which minimizes animal suffering while guaranteeing the integrity of the biological results obtained.

neuroscience↗

bioRxiv2024

Pharmacogenomic screening identifies and repurposes leucovorin and dyclonine as pro-oligodendrogenic compounds in brain repair

Oligodendrocytes are the myelin-forming cells of the central nervous system (CNS), with oligodendroglial pathologies leading to strong disabilities, from early preterm-birth brain injury (PBI) to adult multiple sclerosis (MS). No medication presenting convincing repair capacity in humans has been approved for these pathologies so far. Here, we present a pharmacogenomic approach leading to the identification of small bioactive molecules with a large pro-oligodendrogenic activity, selected through an expert curation scoring strategy (OligoScore) of their large impact on transcriptional programs controlling oligodendrogenesis and (re)myelination. We demonstrate the pro-oligodendrogenic activity of these compounds in vitro, using neural and oligodendrocyte progenitor cell (OPC) cultures, as well as ex vivo, using organotypic cerebellar explant cultures. Focusing on the two most promising molecules, i.e. leucovorin and dyclonine, we tested their therapeutic efficacy using a mouse model of neonatal chronic hypoxia, which faithfully mimics aspects of PBI. In this model, both compounds promoted proliferation and oligodendroglial fate acquisition from neural stem/progenitor cells, with leucovorin also promoting their differentiation. We extended these findings to an adult focal de/remyelination mouse MS model, in which both compounds improved lesion repair by promoting OPC differentiation while maintaining the pool of OPCs, and in parallel, by accelerating the transition from pro-inflammatory to pro-regenerative microglial profiles and myelin debris clearance. This study paves the way for clinical trials aimed at repurposing these FDA-approved compounds to treat myelin pathologies such as PBI and MS. Graphical abstract O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=139 SRC="FIGDIR/small/607135v1_ufig1.gif" ALT="Figure 1"> View larger version (46K): org.highwire.dtl.DTLVardef@83031eorg.highwire.dtl.DTLVardef@141d812org.highwire.dtl.DTLVardef@1d0a31corg.highwire.dtl.DTLVardef@848c67_HPS_FORMAT_FIGEXP M_FIG C_FIG Pharmacogenomic screening identifies and repurposes dyclonine and leucovorin as pro-oligodendrogenic and pro-myelinating compounds. Schematics of the pharmacogenomic approach leading to the identification of small bioactive molecules (compounds) with potential pro-oligodendrogenic activity, followed by the in vitro validation of the top compounds using neural and oligodendrocyte progenitor cell (OPC) cultures as well as organotypic cerebellar explants. The therapeutic efficacy of the top two compounds, leucovorin and dyclonine, both approved by the Food and Drug Administration (FDA), was assessed in vivo using two clinically relevant mouse models of myelin pathologies. In the neonatal hypoxia mouse model, mimicking some aspects of preterm brain injury, both leucovorin and dyclonine promoted neural stem cell (NSC) differentiation into OPCs and OPC proliferation, with leucovorin additionally restoring the density of myelinating OLs found in normoxic conditions. In an adult focal de/remyelination mouse model of multiple sclerosis, both compounds significantly improved lesion repair in adult mice by promoting OPC differentiation while preserving the pool of OPCs, and by accelerating myelin debris clearance and shifting microglia from pro-inflammatory to pro-regenerative profiles.

neuroscience↗

bioRxiv2022

Single cell analysis of the dorsal V-SVZ reveals differential quiescence of postnatal pallial and subpallial neural stem cells driven by TGFbeta/BMP-signalling

The ventricular-subventricular zone (V-SVZ) is the largest neurogenic region of the postnatal forebrain, containing neural stem cells (NSCs) that emerge from both the embryonic pallium and subpallium. Despite of this dual origin, glutamatergic neurogenesis declines rapidly after birth, while gabaergic neurogenesis persists throughout life. Here, we performed single-cell RNA-sequencing (scRNA-Seq) of the postnatal dorsal V-SVZ for unravelling the mechanisms leading to pallial lineage germinal activity silencing. We identify cell lineage-specific NSCs primed for the generation of neurons or glial cells, as well as a large population of so far uncharacterized quiescent NSCs (qNSC). Pallial qNSCs enter a state of deep quiescence, characterized by persistent TGFbeta/BMP signalling, reduced transcriptional activity and Hopx expression, whilst in contrast, subpallial qNSCs remain transcriptionally primed for activation. Induction of deep pallial quiescence is paralleled by a rapid blockade of glutamatergic neuron production and differentiation. Finally, manipulation of the TGFbeta/BMP receptor Bmpr1a demonstrate its key role in mediating these effects at early postnatal times. Together, our results highlight a central role of TGFbeta/BMP-signalling in synchronizing quiescence induction and blockade of neuronal differentiation to rapidly silence pallial germinal activity after birth.

neuroscience↗

bioRxiv2021

Brain virtual histology with X-ray phase-contrast tomography Part I: whole-brain myelin mapping in white-matter injury models

White-matter injury leads to severe functional loss in many neurological diseases. Myelin staining on histological samples is the most common technique to investigate white-matter fibers. However, tissue processing and sectioning may affect the reliability of 3D volumetric assessments. The purpose of this study was to propose an approach that enables myelin fibers to be mapped in the whole rodent brain with microscopic resolution and without the need for strenuous staining. With this aim, we coupled inline (propagation-based) X-ray phase-contrast tomography (XPCT) to ethanol-induced brain sample dehydration. We here provide the proof-of-concept that this approach enhances myelinated axons in rodent and human brain tissue. In addition, we demonstrated that white-matter injuries could be detected and quantified with this approach, using three animal models: ischemic stroke, premature birth and multiple sclerosis. Furthermore, in analogy to diffusion tensor imaging (DTI), we retrieved fiber directions and DTI-like diffusion metrics from our XPCT data to quantitatively characterize white-matter microstructure. Finally, we showed that this non-destructive approach was compatible with subsequent complementary brain sample analysis by conventional histology. In-line XPCT might thus become a novel gold-standard for investigating white-matter injury in the intact brain. This is Part I of a series of two articles reporting the value of in-line XPCT for virtual histology of the brain; Part II shows how in-line XPCT enables the whole-brain 3D morphometric analysis of amyloid-{beta} (A{beta}) plaques. HighlightsO_LIX-ray phase-contrast tomography (XPCT) enables myelin mapping of the whole brain C_LIO_LIXPCT detects and quantifies white-matter injuries in a range of diseases C_LIO_LIFiber directions and anisotropy metrics can be retrieved from XPCT data C_LIO_LIXPCT is compatible with subsequent conventional histology of brain samples C_LIO_LIXPCT is a powerful virtual histology tool that requires minimal sample preparation C_LI Graphical Abstract O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=130 SRC="FIGDIR/small/436852v3_ufig1.gif" ALT="Figure 1"> View larger version (65K): org.highwire.dtl.DTLVardef@1b06ba6org.highwire.dtl.DTLVardef@16b8d4aorg.highwire.dtl.DTLVardef@91cfborg.highwire.dtl.DTLVardef@4dcbca_HPS_FORMAT_FIGEXP M_FIG C_FIG

neuroscience↗

bioRxiv2020

Accelerated dystrophy and decay of oligodendrocyte precursor cells in the APP/PS1 model of Alzheimer's-like pathology

Myelin disruption is a feature of natural aging and of Alzheimers disease (AD). In the CNS, myelin is produced by oligodendrocytes, which are generated throughout life by oligodendrocyte progenitor cells (OPCs). Here, we examined age-related changes in OPCs in APP/PS1 mice, a model for AD-like pathology, compared with non-transgenic (Tg) age-matched controls. Analysis was performed in the CA1 area of the hippocampus following immunolabelling for NG2 with the nuclear dye Hoescht, to identify OPC and OPC sister cells, a measure of OPC replication, together with Gpr17 and Olig2 for oligodendrocytes and myelin basic protein (MBP) immunostaining as a measure of myelination. The results indicate a decrease in the number of OPCs between 9 and 14 months in natural ageing and this occurred earlier at 9 months in APP/PS1 mice, without further decline at 14 months. The number of OPC sister cells was unaltered in natural aging, but declined significantly at 14-months in APP/PS1 mice. The number of GPR17+ and Olig2+ oligodendrocytes was not altered in APP/PS1, whereas MBP immunostaining increased between 9 and 14 months in natural ageing, but not in APP/PS1 mice. Notably, OPCs displayed marked morphological changes at 14 months in APP/PS1 mice, characterized by an overall shrinkage of OPC process domains and increased process branching, characteristic of reactive pathological changes. The results indicate that OPC and myelin disruption are pathological signs in the APP/PS1 mouse model of AD.

neuroscience↗

bioRxiv2020

Synaptic silencing affects the density and complexity of oligodendrocyte precursor cells in the adult mouse hippocampus

Oligodendrocyte progenitor cells (OPCs) are responsible for generating oligodendrocytes, the myelinating cells of the CNS. Life-long myelination is promoted by neuronal activity and is essential for neural network plasticity and learning. OPCs are known to contact synapses and it is proposed that neuronal synaptic activity in turn regulates OPC proliferation and differentiation. To examine this in the adult, we performed unilateral injection of the synaptic blocker botulinum neurotoxin A (BoNT/A) into the hippocampus of adult mice. We confirm BoNT/A cleaves SNAP-25 in the CA1 are of the hippocampus, which has been proven to block neurotransmission. Notably, synaptic silencing by BoNT/A significantly decreased OPC density and caused their shrinkage, as determined by immunolabelling for the OPC marker NG2. Inhibition of synaptic activity resulted in an overall decrease in the number of OPC processes, as well as a decrease in their lengths and branching frequency. These data indicate that synaptic activity is important for maintaining adult OPC numbers and cellular integrity, which is relevant to pathological scenarios characterized by decreased synaptic activity.

neuroscience↗

bioRxiv2020

Astroglia in lateral habenula is essential for antidepressant efficacy of light

Successful antidepressant (AD) treatments are still difficult to achieve. Recently, bright light stimulation (BLS) was shown effective in non-seasonal depression but its mode of action remains elusive. We demonstrate here, using a new mouse model of depression resistant to ADs including ketamine, that chemogenetic activation of lateral habenula (LHb) astroglia prevented the potentiating effect of BLS on the AD response. Additionally, the beneficial action of BLS was associated with upregulation of a specific part of the prefrontal cortex opioid system. These results show that improved behavioral outcome produced by BLS requires habenular astroglia and endogenous opioids as crucial buffer systems.

neuroscience↗

bioRxiv2020

Primate naive pluripotent stem cells stall in the G1 phase of the cell cycle and differentiate prematurely during embryo colonization

After reprogramming to naive pluripotency, human pluripotent stem cells (PSCs) still exhibit very low ability to make interspecies chimeras. Whether this is because they are inherently devoid of the attributes of chimeric competency or because naive PSCs cannot colonize embryos from distant species remains to be elucidated. Here, we have used different types of mouse, human and rhesus monkey naive PSCs and analyzed their ability to colonize rabbit and cynomolgus monkey embryos. Mouse embryonic stem cells (ESCs) remained mitotically active and efficiently colonized host embryos. In contrast, primate naive PSCs colonized host embryos with much lower efficiency. Unlike mouse ESCs, they slowed DNA replication after dissociation and, after injection into host embryos, they stalled in the G1 phase and differentiated prematurely, regardless of host species. We conclude that human and non-human primate naive PSCs do not efficiently make chimeras because they are inherently unfit to remain mitotically active during colonization.

cell biology↗

bioRxiv2018

A pool of postnatally-generated interneurons persists in an immature stage in the olfactory bulb

Calretinin (CR)-expressing periglomerular (PG) cells are the most abundant interneurons in the glomerular layer of the olfactory bulb. They are predominately generated postnatally from the septal and dorsal sub-ventricular zones that continue producing them well into adulthood. Yet, little is known about their properties and functions. Using transgenic approaches and patch-clamp recording we show that CR(+) PG cells of both septal and dorsal origin have homogenous morphological and electrophysiological properties. They express a surprisingly poor repertoire of voltage-activated channels and fire, at most, one action potential. They also receive little synaptic inputs and NMDA receptors predominate at excitatory synapses. These properties, that resemble those of immature neurons, persist over time and limit the contribution of CR(+) PG cells in network activity. Thus, postnatally-generated CR(+) PG cells continuously supply a pool of latent neurons that unlikely participate in olfactory bulb computation but may provide a so far unsuspected reservoir of plasticity.

neuroscience↗