Biology subjects

Mathews, C.

Publications and source records attributed to Mathews, C..

7 recordsLinked to original sources

bioRxiv2025

Age- and Sex- Driven Transcriptional and Metabolic Diversity in Myeloid-Derived Suppressor Cells After Mouse Sepsis

Sepsis induces profound immune dysregulation, often resulting in chronic critical illness characterized by persistent immunosuppression and poor outcomes. Myeloid-derived suppressor cells (MDSCs) are central mediators of this immunosuppressive phenotype, yet the influence of age and sex on their transcriptional and metabolic states remain poorly understood. Here, we employed single-cell RNA sequencing of splenic leukocytes from young (3-4 months) and older (18-24 months) adult male and female mice subjected to a clinically relevant murine sepsis model to define age- and sex-specific MDSC phenotypes. We identified significant differences regarding age and sex in MDSC expansion, transcriptome, canonical pathway activation, RNA velocity, mitochondrial metabolism, and predicted cell-cell communication after sepsis. Using drug2cell analysis of total leukocytes we also identified cohort-specific drug target profiles. These findings underscore the importance of age and sex in shaping sepsis-induced MDSC biology and suggest that personalized immunomodulatory strategies targeting MDSCs could improve sepsis outcomes.

immunology↗

bioRxiv2024

Molecular requirements of chromogranin B for the long-sought anion shunter of regulated secretion

All eukaryotes utilize regulated secretion to release molecular signals packaged in secretory granules for local and remote signaling. An anion shunt conductance was first suggested in secretory granules of bovine chromaffin cells nearly five decades ago. Biochemical identity of this conductance remains undefined. CLC-3, an intracellular Cl-/H+ exchanger, was proposed as a candidate sixteen years ago, which, however, was contested experimentally. Here, we show that chromogranin B (CHGB) makes the kernel of the long-sought anion shunter in cultured and primary neuroendocrine cells and its channel functions are essential to proper granule maturation. Intragranular pH measurements and cargo maturation assays revealed that normal granular acidification, proinsulin-insulin conversion, and dopamine-loading in neuroendocrine cells all rely on functional CHGB+ channels. Primary {beta}-cells from Chgb-/- mice exhibited persistent granule deacidification, which suffices to uplift plasma proinsulin level, diminish glucose-induced 2nd-phase insulin secretion and dwindle monoamine content in chromaffin granules from the knockout mice. Data from targeted genetic manipulations, dominant negativity of a deletion mutant lacking channel-forming parts and tests of CLC-3/5 and ANO-1/2 all exclude CHGB-less channels from anion shunting in secretory granules. The highly conserved CHGB+ channels thus function in regulated secretory pathways in neuronal, endocrine, exocrine and stem cells of probably all vertebrates. HIGHLIGHTSO_LILoss of CHGB channel functions impairs secretory granule acidification in neuroendocrine cells, which necessitates anion shunt conduction. C_LIO_LICHGB{Delta}MIF, a mutant unable to form a functional Cl- channel, exerts negative dominance on endogenous CHGB and results in granule deacidification in cultured cells. C_LIO_LINeither CLC-3 & -5 nor ANO-1 & -2 participate in the CHGB-mediated granule acidification. Clcn3 knockout effects on regulated secretion can be attributed to its functions in endosomal and endolysosomal compartments. C_LIO_LIPrimary Chgb-/- {beta}-cells exhibit persistent granule deacidification, presenting a unifying mechanism for disparate mouse phenotypes: hyperproinsulinemia, near abrogation of 2nd phase insulin release after glucose challenge and diminution of monoamine contents in chromaffin granules. C_LI

cell biology↗

bioRxiv2019

Membrane insertion of chromogranin B for granule maturation in regulated secretion

Regulated secretion serves responses to specific stimuli in eukaryotes. An anion conductance was found essential for maturation and acidification of secretory granules four decades ago, but its genetic identity was unknown. We now demonstrate that chromogranin B (CHGB), an obligate granule protein, constitutes the long-sought anion channel. High-pressure freezing immuno-electron microscopy and biochemical assays showed native CHGB in close proximity to secretory granule membranes, and its membrane-bound and soluble forms both reconstituted Cl- channels. Release of secretory granules delivered CHGB clusters to plasma membranes, which dominate whole-cell anion conductance. Intragranular pH measurements and cargo maturation assays found that CHGB channels supported proinsulin - insulin conversion and dopamine-loading in neuroendocrine cells. {beta}-cells from Chgb-/- mice exhibited significant granule deacidification, accounting for hyperproinsulinemia, altered glucose-tolerance response and lower dopamine concentration in chromaffin granules in these animals. Membrane insertion of well-conserved CHGB is thus indispensable for granule maturation in exocrine, endocrine and neuronal cells. HighlightsO_LINative CHGB is amphipathic and distributes in the lumen and membranes of secretory granules with contrastingly different destinies and functions. C_LIO_LINative CHGB, once delivered to cell surface via granule exocytosis, dominates anion conductance in plasma membranes. C_LIO_LICHGB channels facilitate granule acidification and cargo maturation in cultured and primary neuroendocrine cells. C_LIO_LICHGB channels from bovine, rat and mouse cells all serve the long-missing, intra-organellar anion shunt pathway in the secretory granules for regulated secretion. C_LI

cell biology↗

bioRxiv2019

REAVER: Improved Analysis of High-resolution Vascular Network Images Revealed Through Round-robin Rankings of Accuracy and Precision

Alterations in vascular networks, including angiogenesis and capillary regression, play key roles in disease, wound healing, and development. Imaging of microvascular networks can reveal their spatial structures, but effective study of network architecture requires methods to accurately quantify them using a variety of metrics. We present REAVER (Rapid Editable Analysis of Vessel Elements Routine), a freely available open source tool that researchers can use to analyze and quantify high resolution fluorescent images of blood vessel networks, and assess its performance compared to alternative state-of-the-art image analysis software programs. Top performing programs for each metric are identified by assigning a rank based on statistical multiple comparisons of accuracy and precision, modeled as matches in a round-robin style tournament. This comparison method yields a clearly defined and consistent standard for characterizing program performance, avoiding the use of non-standard ad hoc interpretations of multiple comparisons between programs. Using this comparison method and a dataset of manually analyzed images as a ground-truth, we show that REAVER was the top ranked program for both accuracy and precision for all metrics quantified, including vessel length density, vessel area fraction, mean vessel diameter, and branchpoint count. REAVER can be used to quantify differences in blood vessel architectures between study groups, which makes it particularly useful in experiments designed to evaluate the effects of different external perturbations (e.g. drugs or disease states).

bioinformatics↗

bioRxiv2019

Pericyte Bridges in Homeostasis and Hyperglycemia: Reconsidering Pericyte Dropout and Microvascular Structures

Diabetic retinopathy threatens the vision of a third of diabetic patients. Progression of the disease is attributed to the dropout of pericytes, a cell type that enwraps and stabilizes the microvasculature. In tandem with this presumptive pericyte dropout, there is enriched formation of structures assumed to be remnants of collapsed or regressed vessels, previously classified as acellular capillaries, string vessels, and basement membrane bridges. Instead of endothelial cells, we show that pericytes colocalize with basement membrane bridges, and both bridging structures are enriched by cell-specific knockout of KLF4 and reversibly enriched with elevation of Ang-2, PDGF-BB, and blood sugar. Our data suggests that pericyte counts from retinal digests have misclassified pericyte bridges as endothelial structures and have exaggerated the role of pericyte loss in DR progression. In vivo imaging of corneal limbal vessels demonstrates pericyte migration off-vessel, implicating pericyte movement in formation of pericyte bridges and pathogenesis of diabetic retinopathy.

cell biology↗

bioRxiv2019

Genome-wide analyses indirectly implicate miRNA regulatory mechanisms in Obsessive-compulsive Disorder psychopathology

BackgroundMiRNAs are small, noncoding RNAs possessing the potential to modulate gene expression upon binding to their target messenger RNA (mRNA) constructs, and are known to play a role in the pathogenesis of a range of psychiatric disorders. To date, little work has focused on the role of miRNAs in obsessive-compulsive disorder (OCD). The aim of this study was to assess the potential involvement of miRNAs in OCD psychopathology.\n\nMethodsThe most significant variants (p [≤] 1x10-4) from the Psychiatric Genomics Consortium (PGC) TS/OCD Workgroup OCD meta-analysis were selected and investigated using miRBASE, TargetScan and SNPnexus to determine whether they influence miRNA- mediated regulation in the clinical manifestation of OCD.\n\nResultsTwo-hundred and forty SNPs were identified from the PGC OCD summarystatistics, of which none were found to directly alter miRNA-related gene regulation using in silico analyses. Enrichment analyses identified several potential indirect miRNA-mediated targets associated with both increased (ITPR3: mir-124A) and decreased risk (GPR109A: mir-520A, and mir-525; CGNL1: mir-98 and mir-219).\n\nConclusionmiRNA-mediated regulation was indirectly implicated in the psychopathology of OCD. Enrichment analyses implicates intracellular calcium and immune dysregulation in the clinical manifestation of the disorder and warrants further investigation of the role the immune system may play in the manifestation of disease.

neuroscience↗

bioRxiv2018

Novel organelle anion channels formed by chromogranin B drive normal granule maturation in endocrine cells

All endocrine cells need an anion conductance for maturation of secretory granules. Identity of this family of anion channels has been elusive for forty years. We now show that a family of granule protein, CHGB, serves the long-sought conductance. CHGB interacts with membranes through two amphipathic helices, and forms a chloride channel with large conductance and high anion selectivity. Fast kinetics and high cooperativity suggest that CHGB tetramerizes to form a functional channel. Nonfunctional mutants separate CHGBs function in granule maturation from that in granule biogenesis. In neuroendocrine cells, CHGB channel and a H+-ATPase drives normal insulin maturation inside or dopamine loading into secretory granules. CHGBs tight membrane-association after exocytotic release of secretory granules separates its intracellular function from extracellular functions of its proteolytic peptides. CHGB-null mice show consistent impairment of granule acidification in pancreatic beta-cells. These findings together support that the phylogenetically conserved CHGB proteins constitute a new family of organelle chloride channels in the regulated secretory pathway among various endocrine cells.

cell biology↗