Biology subjects

Velghe, J.

Publications and source records attributed to Velghe, J..

3 recordsLinked to original sources

bioRxiv2026

Mitochondrial transfer mediates metabolic communication between beta cells and islet macrophages

Pancreatic islet macrophages support islet homeostasis and adapt their metabolic program in response to environmental cues, including beta cell released factors. Intercellular mitochondrial transfer is a biological process that modulates cellular responses. To test whether beta cells, which are strongly secretory, transfer mitochondria to islet macrophages, we generated mice with beta cell-specific expression of mitochondrial GFP (PhAMfloxIns1Cre). We demonstrate that beta cells transfer mitochondria to islet macrophages in vivo and in vitro. Diabetogenic stressors did not alter the frequency of mitochondrial transfer and macrophages containing beta cell-derived GFP exhibit increased protein synthesis rates. RNA-seq identified upregulation of activity-regulated cytoskeleton associated protein (Arc) in macrophages receiving beta cell-derived mitochondria, while disruption of actin cytoskeleton dynamics prevented mitochondrial transfer. Together, these findings identify mitochondrial transfer as a previously unrecognized mechanism of beta cell-macrophage communication that may contribute to islet homeostasis and immune regulation.

cell biology↗

bioRxiv2024

Islet amyloid disrupts MHC Class II antigen presentation and protects NOD mice from autoimmune diabetes.

Islet amyloid contributes to beta cell failure in type 2 diabetes through several mechanisms, one being the potent induction of local islet inflammation through activating inflammatory pathways in islet macrophages. We performed an unbiased phenotypic investigation of islet macrophages in the early stage of islet amyloid formation using single cell RNA sequencing of resident islet macrophages in mice with and without the amyloidogenic form of human islet amyloid polypeptide (hIAPP). This revealed that MHC Class II antigen presentation genes were strongly down-regulated in islet macrophages during islet amyloid formation. As islet amyloid has recently been reported in pancreases of people with type 1 diabetes, we sought to investigate the impact of islet amyloid in the NOD mouse model of type 1 diabetes. Both overexpression and physiological expression of hIAPP delayed diabetes in NOD mice relative to littermate controls, corresponding with decreased markers of antigen presentation and activation, as well as decreased immune cell infiltration in islets. Adoptive transfer studies showed that systemic autoimmune function remained intact and beta cells from hIAPP transgenic mice did not evade immune recognition by diabetogenic T cells, collectively indicating the protection from diabetes was mediated by localized disruption of antigen presentation in the pancreas. Consistent with this, incubation of dendritic cells with IAPP aggregates decreased MHC Class II surface expression and diminished antigen-specific T cell activation in vitro, through a phagocytosis-dependent mechanism. Collectively our data show that despite the well-established pro-inflammatory response of macrophages to IAPP aggregates, the uptake of IAPP aggregates during early amyloid formation also disrupts MHC Class II antigen presentation and slows beta cell autoimmunity.

immunology↗

bioRxiv2023

Calcium-dependent transcriptional profiles of human pancreatic islet cells reveal functional diversity in islet subpopulations

Aims/hypothesisPancreatic islets depend on cytosolic calcium to trigger the secretion of glucoregulatory hormones and regulate the transcription of genes important for the response to stimuli. To date, there has not been an attempt to profile calcium-regulated gene expression in all islet cell types. Our aim was to construct a large single-cell transcriptomic dataset from human islets exposed to conditions that would acutely induce or inhibit intracellular calcium signalling, while preserving biological heterogeneity. MethodsWe exposed intact human islets from three donors to the following conditions: (1) 2.8 mM glucose; (2) 25 mM glucose and 40 mM KCl to maximally stimulate calcium signalling; and (3) 25 mM glucose, 40 mM KCl and 5 mM EGTA (calcium chelator) to inhibit calcium signalling, for 1 hour. We sequenced 43,909 cells from all islet cell types, and further subsetted the cells to form an endocrine cell-specific dataset of 32,486 cells expressing INS, GCG, SST or PPY. We compared transcriptomes across conditions to determine the differentially expressed calcium-regulated genes in each endocrine cell type, and in each endocrine cell subcluster of alpha and beta cells. ResultsBased on the number of calcium-regulated genes, we found that each alpha and beta cell cluster had a different magnitude of calcium response. We also showed that a polyhormonal cluster expressing INS, GCG, and SST is defined by calcium-regulated genes specific to this cluster. Finally, we identified the gene PCDH7 from the beta cell clusters that had the highest number of calcium-regulated genes, and showed that cells expressing cell surface PCDH7 protein have enhanced glucose-stimulated insulin secretory function. ConclusionsHere we use our single-cell dataset to show that human islets have cell-type-specific calcium-regulated gene expression profiles, some of them specific to subpopulations. In our dataset, we identify PCDH7 as a novel marker of beta cells having an increased number of calcium-regulated genes and enhanced insulin secretory function. Data availabilityA searchable and user-friendly format of the data in this study, specifically designed for rapid mining of single-cell RNA sequencing data, is available at https://lynnlab.shinyapps.io/Hislet_2023/. The raw data files are available at NCBI Gene Expression Omnibus (GSE196715).

physiology↗