Biology subjects

Guay, C.

Publications and source records attributed to Guay, C..

5 recordsLinked to original sources

bioRxiv2025

Role of small intronic RNAs in the crosstalk between immune cells and beta-cells during type 1 diabetes development

Small non-coding RNAs, such as microRNAs and tRNA-derived fragments, are key regulators of cellular processes, but the functions of small intronic RNAs (sinRNAs), a recently identified RNA class, remain largely unknown. Here, we report that two sinRNAs, sinR-D and sinR-T, are upregulated in pancreatic {beta}-cells of NOD mice, a well-established model of type 1 diabetes. Using in vivo RNA-tagging, we demonstrate that these sinRNAs are packaged into extracellular vesicles released by infiltrating CD4 T lymphocytes and subsequently delivered to {beta}-cells during the early stages of autoimmune attack. Functional analyses revealed that overexpression of sinR-T has little effect on {beta}-cell viability, whereas sinR-D markedly increases {beta}-cell apoptosis. This finding suggests that the transfer of sinR-D contributes to {beta}-cell destruction and the onset of type 1 diabetes. Furthermore, pull-down experiments with biotinylated sinRNAs identified Ago2, a core component of the RNA-induced silencing complex (RISC), as a binding partner of sinR-D, indicating mechanistic parallels with microRNA-mediated regulation. Collectively, our data uncover a novel role for sinRNAs as extracellularly transferred regulators of {beta}-cell fate, expanding the repertoire of small RNAs implicated in the initiation of type 1 diabetes.

molecular biology↗

bioRxiv2025

Small non-coding RNA profiling reveals inflammatory and mitochondrial related changes in aging β-cells and islet macrophages

Aging is accompanied by functional decline and increased senescence of pancreatic {beta}-cells. These changes may be influenced by islet-resident macrophages (iMACs) that remodel tissue in response to environmental cues. To explore the molecular mechanisms underlying {beta}-cell aging and senescence, we profiled small non-coding RNAs (sncRNAs) in FACS-sorted {beta}-cells and iMACs from 3-, 12-, and 22-month-old mouse islets or from senescence-associated {beta}gal (SA-{beta}gal) positive {beta}-cells of 8-month-old mice. Overall, senescent {beta}-cells displayed distinct sncRNA signatures that only partially overlapped with those of aging. However, several miRNAs previously found to be deregulated in obese or diabetic conditions were modulated in both aging and senescent {beta}-cells, including upregulation of miRNAs linked to inflammation. In vitro exposure to pro-inflammatory cytokines partially reproduced these profiles. Aging also reshaped the {beta}-cell tRNA-derived fragment (tRF) pool, enhancing global mitochondrial tRF levels. Interestingly, some changes in miRNAs and tRFs were {beta}-cell specific, whereas others occurred also in other aged metabolic tissues. iMACs also showed age-related sncRNA remodeling, including upregulation of anti-inflammatory miRNAs and mitochondrial tRFs, suggesting adaptive immune reprogramming. Together, these data reveal a profound, coordinated reshaping of the sncRNA landscape in {beta}-cells and iMACs during aging, offering new insights into molecular mechanisms driving age-related islet dysfunction.

molecular biology↗

bioRxiv2025

The MIME-seq technique allows to monitor the interaction of small non-coding RNAs with Argonaute proteins and their transfer to other cells

The MIME-seq2.0 technique utilizes a chimeric HENMT1 methyltransferase engineered to bind to Argonaute proteins (hereafter referred to MIME enzyme) to protect the terminal sugar of small non-coding RNAs (sncRNAs) from oxidation, a reaction that inhibits unmodified RNA ligation and cloning. In this study, we confirm that the MIME-seq technique efficiently distinguishes oxidized and non-oxidized sncRNAs. Indeed, expression of the MIME enzyme in the insulin-secreting cell line MIN6B1 protected miRNAs from oxidation and permitted their detection by RNA sequencing and quantitative PCR. Comparison of the sncRNA profile between wild type and MIME-expressing cells demonstrated protection from oxidation not only of miRNAs, but also of some Y-RNA and tRNA-derived fragments. Immunoprecipitation with Ago2 antibodies confirmed that the protected Y-RNA and tRNA fragments bind to Argonaute proteins. We also used this system to track miRNA transfer between cells via extracellular vesicles (EVs). miRNAs released inside EVs of MIME-expressing Jurkat T cells or C2C12 myotubes and delivered to MIN6B1 cells were protected from oxidation, enabling sensitive and specific detection of the transferred miRNAs in the receiving cells. Overall, the MIME-seq technique provides a powerful tool for analyzing small RNA binding to Argonaute proteins in living cells and offers new possibilities for tracking RNA transfer across different cell types.

molecular biology↗

bioRxiv2025

5'tRNA-derived fragments modulate β-cell homeostasis and islet macrophage activation in type 2 diabetes

During obesity and type 2 diabetes, pancreatic {beta}-cells face chronic environmental stress, while islet-resident macrophages (iMACs) undergo metabolic reprogramming that exacerbates {beta}-cell dysfunction. Stress-induced cleavage of transfer RNAs (tRNAs) generates tRNA-derived fragments (tRFs), whose role in this context is not fully understood. We identify elevated levels of 5tRFGlu(CTC) and 5tRFGly(GCC) in {beta}-cells and iMACs from db/db mice and in islets from type 2 diabetic patients. Notably, 5tRFGlu(CTC) is also induced under prediabetic conditions and inversely correlates with insulin secretion. Lipotoxic stress triggers their production via Angiogenin-mediated cleavage. Blocking 5tRFGlu(CTC) in islets protects against {beta}-cell apoptosis and restores insulin secretion under palmitate stress. Using a {beta}-cell/macrophage co-culture system, we show that {beta}-cell contact shapes a unique macrophage phenotype (iMAC-like) that shifts upon palmitate exposure--recapitulating in vivo observations. Inhibiting 5tRFGlu(CTC) in iMAC-like cells prevents this activation switch, reduces {beta}-cell stress, and improves insulin secretion. Mechanistically, 5tRFGlu(CTC) interacts with RNA-binding proteins to regulate transcriptional and post-transcriptional pathways linked to immune activation, extracellular matrex remodeling, neurogenesis, and oxidative stress. Our study identifies 5tRFs as key mediators of islet microenvironment remodeling in diabetes, offering new insights into intercellular stress signaling in metabolic disease.

cell biology↗

bioRxiv2019

Chromatin accessibility variations across pancreatic islet maturation

Glucose-induced insulin secretion, a peculiar property of fully mature {beta}-cells, is only achieved after birth and is preceded by a phase of intense proliferation. These events occurring in the neonatal period are decisive for the establishment of an appropriate functional {beta}-cell mass that provides the required insulin throughout life. However, key regulators of gene expression involved in cellular reprogramming along pancreatic islet maturation remain to be elucidated. The present study addressed this issue by mapping open chromatin regions in newborn versus adult rat islets using the ATAC-seq assay. Accessible regions were then correlated with the expression profiles of mRNAs to unveil the regulatory networks governing functional islet maturation. This led to the identification of Scrt1, a novel transcriptional repressor controlling {beta}-cell proliferation.

genomics↗