Biology subjects

Sorokin, L.

Publications and source records attributed to Sorokin, L..

5 recordsLinked to original sources

bioRxiv2025

Vascular Basement Membrane Laminins Modulate Functional Zonation of Cerebral Microvessels

We investigated whether vascular basement membrane (BM) laminins influence vascular zonation by performing single-cell RNA sequencing on cerebral blood vessels from mice lacking the major vascular laminins in endothelial and smooth muscle BMs, laminin 4 (Lama4-/-) and laminin 5 (Tek-cre:Lama5-/-), and wild-type littermates. Our dataset expands existing cerebral vascular transcriptomic profiles and reveals that Lama4-/- endothelial cells exhibit increased arterial marker expression and reduced postcapillary venule identity. In vitro and in vivo studies indicate that compensatory upregulation of laminin 5 in Lama4-/-vessels enhances expression of junctional proteins (Ocln, Cldn5) and promotes vessel contractility via increased expression of contractile molecules in mural cells. Additionally, loss of Lama4 upregulates expression of large artery markers (Gja4, Dll4, Tgfb2) and results in elevated autotaxin (Enpp2) levels, a key enzyme in lysophosphatidic acid production implicated in stroke. Accordingly, Lama4-/- mice exhibit worsened stroke outcomes, driven not by immune infiltration or junctional defects, but by increased vascular permeability likely mediated by autotaxin and/or activation of resident myeloid cells. Our data suggest that laminin 4/5 ratios in vascular BMs regulate functional zonation between arterioles, capillaries and postcapillary venules by modulating metabolic pathways in endothelial and mural cells, and indirectly influencing resident myeloid cells.

cell biology↗

bioRxiv2022

Single cell transcriptomics reveals functionally specialized vascular endothelium in brain

The blood-brain barrier (BBB) limits the entry of leukocytes and potentially harmful substances from the circulation into the central nervous system (CNS). While BBB defects are a hallmark of many neurological disorders, the cellular heterogeneity at the neurovascular interface and the mechanisms governing neuroinflammation are not fully understood. Through single cell RNA sequencing of non-neuronal cell populations of the murine cerebral cortex during development, adulthood, ageing and neuroinflammation, we identify reactive endothelial venules (REVs), a compartment of specialised post-capillary endothelial cells (ECs) that are characterized by consistent expression of cell adhesion molecules, preferential leukocyte transmigration, association with perivascular macrophage populations, and endothelial activation initiating CNS immune responses. Our results provide novel insights into the heterogeneity of the cerebral vasculature and a useful resource for the molecular alterations associated with neuroinflammation and ageing.

physiology↗

bioRxiv2021

ECM-integrin signalling instructs cellular position-sensing to pattern the early mouse embryo

Development entails patterned emergence of diverse cell types within the embryo. In mammals, cells positioned inside the embryo gives rise to the inner cell mass (ICM) that eventually forms the embryo proper. Yet the molecular basis of how these cells recognise their inside position to instruct their fate is unknown. Here we show that cells perceive their position through extracellular matrix (ECM) and integrin-mediated adhesion. Provision of ECM to isolated embryonic cells induces ICM specification and alters subsequent spatial arrangement between epiblast (EPI) and primitive endoderm (PrE) cells that emerge within the ICM. Notably, this effect is dependent on integrin {beta}1 activity and involves apical to basal conversion of cell polarity. We demonstrate that ECM-integrin activity is sufficient for inside positional signalling and it is required for proper sorting of EPI/PrE cells. Our findings thus highlight the significance of ECM-integrin adhesion in enabling position-sensing by cells to achieve tissue patterning.

developmental biology↗

bioRxiv2020

Endothelial basement membrane laminins as an environmental cue in monocyte differentiation to macrophages.

Monocyte differentiation to macrophages is triggered by migration across the endothelial barrier, which is constituted by both endothelial cells and their underlying basement membrane. We address here the role of the endothelial basement membrane laminins (laminins 411 and 511) in this monocyte to macrophage switch. Chimeric mice carrying CX3CR1-GFP bone marrow were employed to track CCL2-induced monocyte extravasation in a cremaster muscle model using intravital microscopy, revealing faster extravasation in mice lacking endothelial laminin 511 (Tek-cre::Lama5-/-) and slower extravasation in mice lacking laminin 411 (Lama4-/-). CX3CR1-GFPlow extravasating monocytes were found to have a higher motility at laminin 511 low sites and to preferentially exist vessels at these sites. However, in vitro experiments reveal that this is not due to effects of laminin 511 on monocyte migration mode nor on the tightness of the endothelial barrier. Rather, using an intestinal macrophage replenishment model and in vitro differentiation studies we demonstrate that laminin 511 together with the attached endothelium collectively promote monocyte differentiation to macrophages. Macrophage differentiation is associated with a change in integrin profile, permitting differentiating macrophages to distinguish between laminin 511 high and low areas and to migrate preferentially across laminin 511 low sites. These studies highlight the endothelial basement membrane as a critical site for monocyte differentiation to macrophages, which may be relevant to the differentiation of other cells at vascular niches.

immunology↗

bioRxiv2016

Fractone bulbs derive from ependymal cells and their laminin composition affects cell proliferation in the subventricular zone

Fractones are extracellular matrix structures in the neural stem cell niche of the subventricular zone (SVZ), where they appear as round deposits named bulbs or thin branching lines called stems. Their cellular origin and what determines their localization at this site is poorly studied and it remains unclear whether they influence neural stem and progenitor cells formation, proliferation and/or maintenance. To address these questions, we analyzed whole mount preparations of the lateral ventricle by confocal microscopy using different extracellular matrix and cell markers. We found that bulbs are rarely connected to stems and that they contain laminin 5 and 2 chains, respectively. Fractone bulbs were profusely distributed throughout the SVZ and appeared associated with the center of pinwheels, a critical site for adult neurogenesis. We demonstrate that bulbs appear at the apical membrane of ependymal cells at the end of the first week after birth. The use of transgenic mice lacking laminin 5 gene expression (Lama5) in endothelium and in FoxJ1-expressing ependymal cells, revealed ependymal cells as the source of laminin 5-containing fractone bulbs. Loss of laminin 5 from bulbs correlated with a 60% increase in cell proliferation, as determined by PH3 staining, and with a selective reduction in the number of quiescent neural stem cells in the SVZ. These results indicate that fractones are a key component of the SVZ and suggest that laminin 5 modulates the physiology of the neural stem cell niche.\n\nSignificance StatementOur work unveils key aspects of fractones, extracellular matrix structures present in the SVZ that still lack a comprehensive characterization. We show that fractones extensively interact with neural stem cells, whereas some of them are located precisely at pinwheel centers, which are hotspots for adult neurogenesis. Our results also demonstrate that fractones increase in size during aging and that their interactions with NSPCs become more complex in old mice. Lastly, we show that fractone bulbs are produced by ependymal cells and that their laminin content regulates neural stem cells.

neuroscience↗