Biology subjects

Montagne, A.

Publications and source records attributed to Montagne, A..

8 recordsLinked to original sources

bioRxiv2026

Selective granzyme B replenishment dominates the molecular switch for sustained cytotoxicity in effector CD8+ T lymphocytes

Cytotoxic T lymphocytes (CTLs) are highly efficient multiple killer cells, yet how they sustain killing after the initial discharge of canonical lytic granules remains incompletely understood. Late-phase cytotoxicity is often attributed to death receptor signaling or cytokine-mediated mechanisms, but whether CTLs also remodel their intrinsic cytotoxic machinery during prolonged engagement remains unclear. Here, we show that human CTLs maintain cytotoxic resilience through selective remodeling of their lytic program, marked by preferential preservation of granzyme B (GzmB). Following acute degranulation and reduction of mature perforin, CTLs selectively replenish GzmB through de novo protein synthesis, whereas perforin and several other granule-associated components show limited restoration. Replenished GzmB becomes redistributed into vesicular compartments with reduced overlap with mature perforin and is delivered to successive targets during sustained cytotoxic responses. Under conditions of limited detectable mature perforin, CTLs continue to deliver enzymatically active GzmB, induce altered calcium responses in target cells, and support productive but kinetically heterogeneous killing. This GzmB-preserved effector state is maintained and further accentuated during engagement with resistant melanoma cells. Together, our findings identify selective GzmB renewal as a central feature of sustained CTL cytotoxicity and reveal an adaptive remodeling of the cytotoxic machinery that may support CTL resilience during prolonged immune responses.

immunology↗

bioRxiv2026

Pericyte Loss Reprogrammes Capillary Endothelium and Drives White Matter Injury in Small Vessel Disease

Pericytes are critical regulators of cerebrovascular homeostasis, yet their contribution to small vessel disease (SVD) and white matter injury remains incompletely understood. Here, we use an inducible Atp13a5-driven genetic strategy to selectively label and ablate brain pericytes, enabling integrated morphological, functional, and transcriptomic analyses across the neurogliovascular unit. Single-cell RNA sequencing and tissue-level mapping identified distinct pericyte subtypes distributed along the vascular tree and revealed subtype-specific vulnerability following depletion. Moderate pericyte loss induced transient cerebrovascular dysfunction characterised by reduced cerebral blood flow and increased blood-brain barrier (BBB) permeability, accompanied by delayed white matter abnormalities, including altered diffusion MRI metrics, oligodendrocyte progenitor cell responses, and myelin loss. At the molecular level, pericyte depletion reprogrammed capillary endothelial cells toward an activated venular-like state characterised by VCAM-1 induction, reduced expression of the BBB-associated transporter MFSD2A, and activation of type I interferon signalling pathways. Cross-species analyses revealed enrichment of human white matter hyperintensity-associated SVD gene signatures across endothelial subtypes following pericyte depletion. Together, these findings identify pericyte dysfunction as a driver of endothelial inflammatory remodelling and white matter injury and establish mechanistic links between microvascular pericyte loss and human SVD.

neuroscience↗

bioRxiv2026

Abrupt Pericyte Loss Precedes Endothelial Activation in Cerebral Small Vessel Disease

Cerebral small vessel disease (cSVD) is a leading cause of stroke and vascular cognitive impairment, yet the cellular mechanisms underlying microvascular dysfunction in human disease remain incompletely understood. In particular, the relationship between pericyte alterations and endothelial activation, two key features of blood-brain barrier dysfunction, remains unresolved. Here, we performed a quantitative single-vessel analysis of the human cortical microvasculature across increasing cSVD severity and ageing. Using multiplex immunohistochemistry combined with spectral unmixing and automated image analysis, we analysed 11,409 microvascular fragments from post-mortem brain tissue derived from 20 cases. Endothelial cells, pericytes, and endothelial activation were assessed using PECAM-1, PDGFR{beta}, and VCAM-1, respectively. Microvascular density and diameter differed between cortical grey matter and the underlying white matter, with white matter vessels being less dense and wider in controls. While vessel diameter remained stable across disease stages, microvascular density increased with cSVD severity and age in the white matter. At the molecular level, PDGFR{beta} signal decreased markedly with increasing cSVD severity, consistent with progressive pericyte loss. This reduction was observed in both grey and white matter and correlated with disease severity and age. Notably, intermediate disease groups displayed marked heterogeneity, with vessels exhibiting either preserved or near-complete pericyte coverage, suggesting a potentially bimodal transition. In parallel, endothelial markers PECAM-1 and VCAM-1 increased significantly with disease severity, reflecting endothelial activation. Unsupervised Gaussian mixture clustering of marker expression identified three vascular states characterised by (i) preserved pericytes with low endothelial activation, (ii) marked pericyte loss without endothelial activation, and (iii) combined pericyte depletion and endothelial activation. These clusters broadly aligned with clinical severity but revealed intermediate states not captured by post-mortem diagnosis alone. Together, these findings suggest that pericyte loss and endothelial activation are partially dissociated processes that occur in a sequential progression in human cSVD, supporting pericyte dysfunction as an early event and highlighting it as a potential therapeutic target in microvascular disease.

pathology↗

bioRxiv2026

Placental prostaglandin signaling disrupts barrier integrity and relays an acute inflammatory signal to the fetus.

Maternal inflammation during pregnancy is a major risk factor for adverse neurodevelopmental outcomes, yet the mechanisms linking maternal immune activation (MIA) to placenta-fetal brain axis dysfunction remain unclear. Using a poly-(I:C) mouse model, we show that MIA rapidly disrupts placental-blood barrier (PBB) integrity by disrupting pericyte-endothelium coupling within 48 hours, leading to increased placental permeability detected by in vivo MRI. We identify a prostaglandin E2 (PGE2)-dependent pathway involving cyclooxygenase-2 (COX2) and prostaglandin E-synthase (mPGES1) as a key mediator of this effect. Pharmacological inhibition of COX2 prevented MIA-induced structural and functional changes. In vitro explant studies confirmed that PGE2 acts via the EP3 receptor to disrupt pericyte-endothelium interactions, while ex vivo perfusion demonstrated that in addition to its local effects on PBB structure, placenta-derived PGE2 enters the fetal circulation. Finally, similar vascular alterations were observed in human placentas from pregnancies with severe maternal inflammation. These findings reveal a conserved inflammatory mechanism that compromises PBB integrity and may relay signals to the fetal brain, highlighting potential therapeutic targets for neuroprotection during prenatal inflammation. One Sentence SummaryMaternal immune activation during pregnancy disrupts placental vascular integrity through a COX2-dependent prostaglandin E2 pathway, which compromises the placenta-blood barrier and relays inflammatory signals to the fetus, identifying potential therapeutic targets for neuroprotection.

developmental biology↗

bioRxiv2026

APOE4 Genotype is Associated with Reduced Cortical VEGFR2 (KDR) Transcript Levels Independent of Endothelial Abundance: An AMP-AD RNA-seq Pilot Study

BackgroundApolipoprotein E4 (APOE4) is the strongest common genetic risk factor for late-onset Alzheimers disease and has been implicated in cerebrovascular dysfunction. Vascular endothelial growth factor receptor 2 (VEGFR2), encoded by the gene KDR, is a key regulator of endothelial integrity and blood-brain barrier (BBB) maintenance; however, its relationship to APOE4 status in human brain tissue remains unclear. MethodsBulk RNA-sequencing data from 162 donors (n = 633 cortical samples) from the AMP-AD MSSB cohort were analysed using linear mixed-effects models with donor-level random intercepts. Models were adjusted for tissue region, age at death, sex, RNA integrity (RIN), and post-mortem interval. An endothelial composite score derived from key endothelial markers (PECAM1, VWF, CLDN5, FLT1, TEK) was included to account for endothelial signal abundance. Interaction models assessed modification by cortical region and neuropathological burden (Braak stage, CERAD score, plaque mean). A candidate panel of endothelial/BBB transcripts (KDR, CAV1, MFSD2A, CLDN5, SLC2A1, OCLN, TJP1) were also assessed in relation to APOE genotype. ResultsBulk KDR expression varied significantly across cortical regions (p < 2x10-16) and was strongly correlated with endothelial signal abundance (r = 0.57, p < 2x10-16). APOE4 status was not associated with endothelial composite score (p = 0.78). In models adjusting for tissue and technical covariates, but not endothelial signal, APOE4 carriers showed a non-significant trend toward reduced KDR expression ({beta} = -0.16, p = 0.064). After inclusion of the endothelial composite score, APOE4 carrier status was significantly associated with reduced KDR expression ({beta} = -0.17, p = 0.029), corresponding to an estimated 10-15% decrease in transcript levels. The direction of effect was consistent across cortical regions, with no evidence of APOE4 x region interaction. No significant APOE4 x neuropathology interactions were observed. Among candidate transcripts, only KDR and TJP1 showed reduced expression, suggesting a selective rather than global transcriptional effect. ConclusionsBulk KDR transcript levels are strongly influenced by endothelial signal abundance; however, APOE4 is associated with a modest but consistent reduction in VEGFR2 expression independent of endothelial signal abundance and neuropathological severity. These findings support a model in which APOE4 contributes to vascular dysfunction through targeted endothelial alterations, rather than merely reflecting changes in endothelial cell proportion.

neuroscience↗

bioRxiv2023

Molecular signature and functional properties of human pluripotent stem cell-derived brain pericytes

Brain pericytes maintain the blood-brain barrier (BBB), secrete neurotrophic factors and clear toxic proteins. Their loss in neurological disorders leads to BBB breakdown, neuronal dysfunction, and cognitive decline. Therefore, cell therapy to replace lost pericytes holds potential to restore impaired cerebrovascular and brain functions. However, the molecular composition and function of human iPSC-derived brain pericytes (iPSC-PC) remains poorly characterized. Here, we show by a quantitative analysis of 8,344 proteins and 20,572 phosphopeptides that iPSC-PC share 96% of total proteins and 98% of protein phosphorylation sites with primary human brain pericytes. This includes cell adhesion and tight junction proteins, transcription factors, and different protein kinase families of the human kinome. In pericyte-deficient mice, iPSC-PC home to host brain capillaries to form hybrid human-mouse microvessels with ligand-receptor associations. They repair BBB leaks and protect against neuron loss, which we show requires PDGRFB and pleiotrophin. They also clear Alzheimers amyloid-{beta} and tau neurotoxins in an ex vivo brain slice assay via lipoprotein receptor. Thus, iPSC-PC may have potential as a replacement therapy for pericyte-deficient neurological disorders.

neuroscience↗

bioRxiv2022

A palmitate-rich metastatic niche enables metastasis growth via p65 acetylation

Cancer cells outgrowing in distant organs of metastasis rewire their metabolism to fuel on the available nutrients. While this is often considered an adaptive pressure limiting metastasis formation, some nutrients available at the metastatic site naturally or through changes in organ physiology may inherently promote metastatic growth. We find that the lung, a frequent site of metastasis, is a lipid-rich environment. Moreover, we observe that pathological conditions such as pre-metastatic niche formation and obesity further increase the availability of the fatty acid palmitate in the lung. We find that targeting palmitate processing inhibits spheroid growth in vitro and metastasis formation in lean and obese mice. Mechanistically, we discover that breast cancer cells use palmitate to synthesize acetyl-CoA in a carnitine palmitoyltransferase 1a (CPT1a)-dependent manner. Lysine acetyltransferase 2a (KAT2a), whose expression is promoted by palmitate availability, relies on the available acetyl-CoA to acetylate the NF-{kappa}B subunit p65. This favors nuclear location of p65 and activates a pro-metastatic transcriptional program. Accordingly, deletion of KAT2a phenocopies CPT1a silencing in vitro as well as in vivo and patients with breast cancer show co-expression of both proteins in metastases across palmitate-rich metastatic sites. In conclusion, we find that palmitate-rich environments foster metastasis growth by increasing p65 acetylation resulting in elevated NF-{kappa}B signaling.

cancer biology↗

bioRxiv2021

Atp13a5 Marker Reveals Pericytes of The Central Nervous System in Mice

Perivascular mural cells including vascular smooth cells (VSMCs) and pericytes are integral components of the vascular system. In the central nervous system (CNS), pericytes are also known as the guardian of the blood-brain barrier, blood-spinal cord barrier and blood-retinal barrier, and play key roles in maintaining cerebrovascular and neuronal functions. However, the functional difference between CNS and peripheral pericytes has not been resolved at the genetic and molecular levels. Hence, the generation of reliable CNS pericyte-specific models and genetic tools remains very challenging. Here, we report a new CNS pericyte marker in mice. This cation-transporting ATPase 13A5 (Atp13a5) marker is highly specific to the pericytes in brain, spinal cord and retina. We generated a transgenic model with a knock-in tdTomato reporter and Cre recombinase. The tdTomato reporter reliably labels the CNS pericytes, but not found in any other CNS cell types including closely related VSMCs, or in peripheral organs. More importantly, Atp13a5 is turned on at embryonic day E15, suggesting brain pericytes are shaped by the developing neural environment. We hope that the new tools will allow us to further explore the heterogeneity of pericytes and achieve a better understanding of CNS pericytes in health and diseases.

neuroscience↗