Biology subjects

Lambertini, L.

Publications and source records attributed to Lambertini, L..

6 recordsLinked to original sources

bioRxiv2026

Epigenetic Profiling of Human Insulinomas Reveals AP-1 Family as Critical Regulators of Beta Cell Maturation

Insulinomas are rare and benign human pancreatic adenomas that overproduce insulin and display increased beta cell mass. We and others have shown that transcriptomic and genomic profiling on insulinomas provides a data mine for identifying targets that can be manipulated to induce human beta cell regeneration. Majority of causative genetic variants in insulinomas involve epigenetic regulatory genes. Yet, specifically how these variants lead to human beta cell expansion and increased function is largely unknown. Here, we performed bulk and single-nucleus epigenomic and transcriptomic profiling to define regulatory alterations in human insulinomas. Bulk ATAC-seq and H3K27Ac ChIP-seq revealed significant enrichment of AP-1 transcription factor binding motifs within beta cell-associated open chromatin/enhancer regions in normal islets, accompanied by robust expression of AP-1 family members; in contrast, insulinomas exhibited marked reductions in both AP-1 motif enrichment and AP-1 expression. Our snRNA-seq and snATAC-seq profiling across four independent insulinomas identified a consistent and previously unrecognized signature defined by suppression of AP-1 transcription factors and widespread loss of chromatin accessibility at AP-1 binding sites, particularly at enhancers governing beta cell identity. Collectively, these results establish AP-1-mediated regulatory programs as critical determinants of beta cell maturation and define their disruption as a signature among human insulinomas.

molecular biology↗

bioRxiv2025

Harmine Selectively Drives Human Beta Cell Differentiation and Function Via Protein Kinase A Pathways

Harmine and other small molecule inhibitors of the kinase DYRK1A induce human beta cells to replicate and regenerate in vitro and in vivo, and are effective at reversing diabetes in animal models. In addition to its beta cell proliferative and regenerative effects, harmine also induces expression of transcription factors and other genes involved in beta cell differentiation and function, exemplified by PDX1, MAFA, NKX6.1, GLP1R, PCSK1 and many others. Harmine also rapidly enhances glucose-stimulated insulin secretion in vitro and in vivo, reversing diabetes within days in diabetic mice transplanted with a marginal mass of human islets. We had assumed that this pro-differentiation or pro-function effect was a common feature of all DYRK1A inhibitors, and was mediated by DYRK1A inhibition. Thus, DYRK1A is a primary target (we refer to it as Target 1) for harmine. Here, to our surprise, we report that the pro-differentiation effect is not a generalized action for all small molecule DYRK1A inhibitors and does not result from DYRK1A interference or genetic silencing. Instead, the prodifferentiation effect is restricted to a small select subset of DYRK1A inhibitors (harmine, 2-2c and 5-IT). Remarkably, the pro-differentiation effect results from the unique ability of these drugs to activate protein kinase A (PKA), a dual mechanism that distinguishes this class from other DYRK1A inhibitors. The beneficial effects of harmine on PKA appear to be indirect, driven by an as yet unidentified, Target 2 in the PKA pathway. These findings make it clear that all DYRK1A inhibitors are not interchangeable, and that those that drive both proliferation and differentiation/function will likely be preferable in human clinical therapeutic settings. They also provide a novel target or roadmap for enhancing human beta cell differentiation in Type 1 and Type 2 diabetes. Graphical Abstract O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=140 SRC="FIGDIR/small/692818v1_ufig1.gif" ALT="Figure 1"> View larger version (23K): org.highwire.dtl.DTLVardef@bd015corg.highwire.dtl.DTLVardef@a46f9borg.highwire.dtl.DTLVardef@19b4f65org.highwire.dtl.DTLVardef@179aa28_HPS_FORMAT_FIGEXP M_FIG C_FIG

cell biology↗

bioRxiv2025

Nutrient excess remodels islet autonomic innervation via pancreatic schwann cells

Nutrient excess results in short- and long-term adaptations in the structure and function of metabolic organs, such as pancreatic islets. Pancreatic innervation contributes to islet architecture and function in many species, including humans, but little is known about its adaptation to over-nutrition. Here, we use 3D imaging to show that short-term high fat diet rapidly remodels islet sympathetic innervation while long-term high fat diet results in islet-specific cholinergic neuropathy. Using highly targeted, organ- and circuit-specific approaches, we demonstrate that remodeling of pancreatic innervation contributes to impaired glycemic control with short- and long-term nutrient excess. Counteracting the nutrient-induced changes in sympathetic and parasympathetic inputs to the pancreas using neuromodulation and repurposed FDA-approved approaches, we can significantly improve glycemic control even with long-term high fat diet. Finally, we identify islet Schwann cells as a source of the neurotrophic factor, S100b, contributing to rapid sympathetic hyperinnervation with short-term overnutrition. Our findings reveal novel adaptations in islet innervation contributing to nutrition-mediated metabolic dysfunction that can be ameliorated by targeting pancreatic neural circuits.

physiology↗

bioRxiv2024

Select DYRK1A Inhibitors Enhance Both Proliferation and Differentiation in Human Pancreatic Beta Cells

The small molecule DYRK1A inhibitor, harmine, induces human beta cell proliferation, expands beta cell mass, enhances expression of beta cell phenotypic genes, and improves human beta cell function in vitro and in vivo. It is unknown whether the "pro-differentiation effect" is a DYRK1A inhibitor class-wide effect. Here we compare multiple commonly studied DYRK1A inhibitors. Harmine, 2-2c and 5-IT increase expression of PDX1, MAFA, NKX6.1, SLC2A2, PCSK1, MAFB, SIX2, SLC2A2, SLC30A8, ENTPD3 in normal and T2D human islets. Unexpectedly, GNF4877, CC-401, INDY, CC-401 and Leucettine fail to induce expression of these essential beta cell molecules. Remarkably, the pro-differentiation effect is independent of DYRK1A inhibition: although silencing DYRK1A induces human beta cell proliferation, it has no effect on differentiation; conversely, harmine treatment enhances beta cell differentiation in DYRK1A-silenced islets. A careful screen of multiple DYRK1A inhibitor kinase candidate targets was unable to identify pro-differentiation pathways. Overall, harmine, 2-2c and 5-IT are unique among DYRK1A inhibitors in their ability to enhance both beta cell proliferation and differentiation. While beta cell proliferation is mediated by DYRK1A inhibition, the pro-differentiation effects of harmine, 2-2c and 5-IT are distinct, and unexplained in mechanistic terms. These considerations have important implications for DYRK1A inhibitor pharmaceutical development.

molecular biology↗

bioRxiv2023

Single Cell RNA-Seq Analysis of Regenerative Drug-Treated Human Pancreatic Islets Identifies A Cycling Alpha Cell Population As Key Beta Cell Progenitors

Diabetes ultimately results from an inadequate number of functional, insulin-producing human beta cells. Although current attempts to replenish the remaining beta cell pool in people with diabetes are encouraging, scalability and cost limit access for the millions of people with diabetes. The small molecule DYRK1A inhibitor class of beta cell regenerative drugs, either alone or in combination with GLP1 receptor agonists or TGF{beta} superfamily inhibitors, are capable of inducing beta cell replication in vitro and increasing beta cell mass in vivo. Despite these advances, the precise mechanisms of action of DYRK1A inhibitors remain incompletely understood. To address the mechanisms more deeply, we performed single cell RNA sequencing on human pancreatic islets treated with a DYRK1A inhibitor, either alone, or in combination with a GLP1 receptor agonist or a TGF{beta} superfamily inhibitor. We identify a cluster of Cycling Alpha Cells as the cells most responsive to DYRK1A inhibition. Velocity and pseudotime lineage trajectory analyses suggest that Cycling Alpha Cells serve as the primary target cell type for of DYRK1A inhibitors, and may serve as precursor cells that transdifferentiate into functional human beta cells in response to the DYRK1A inhibition. In addition to providing a novel mechanism of action for DYRK1A inhibitors, our findings suggest that efforts to target regenerative drugs to human beta cells may be mis-directed: the proper target may be Cycling Alpha Cells.

cell biology↗

bioRxiv2017

Cadmium-associated differential methylation throughout the placental genome: epigenome-wide association study of two US birth cohorts

BackgroundCadmium (Cd) is a ubiquitous toxicant that during pregnancy can impair fetal development. Cd sequesters in the placenta where it can impair placental function, impacting fetal development. We aimed to investigate Cd-associated variations in placental DNA methylation (DNAM), associations with gene expression, and identify novel pathways involved in Cd-associated reproductive toxicity.\n\nMethodsUsing placental DNAM and Cd concentrations in the New Hampshire Birth Cohort Study (NHBCS, n=343) and the Rhode Island Child Health Study (RICHS, n=141), we performed an EWAS between Cd and DNAM, adjusting for tissue heterogeneity using a reference-free method. Cohort-specific results were aggregated via inverse variance weighted fixed effects meta-analysis, and variably methylated CpGs were associated with gene expression. We then performed functional enrichment analysis and tests for associations between gene expression and birth metrics.\n\nResultsWe identified 17 Cd-associated differentially methylated CpG sites with meta-analysis p-values < 1e-05, two of which were within a 5% false discovery rate (FDR). Methylation levels at 9 of the 17 loci were associated with increased expression of 6 genes (5% FDR): TNFAIP2, EXOC3L4, GAS7, SREBF1, ACOT7, and RORA. Higher placental expression of TNFAIP2 and ACOT7, and lower expression of RORA, were associated with lower birth weight z-scores (p-values < 0.05).\n\nConclusionCd associated differential DNAM and corresponding DNAM-expression associations at these loci are involved in inflammatory signaling and cell growth. The expression levels of genes involved in inflammatory signaling (TNFAIP2, ACOT7, and RORA), were also associated with birth metrics, suggesting a role for inflammatory processes in Cd-associated reproductive toxicity.\n\nSignificanceCadmium is a toxic environmental pollutant that can impair fetal development. The mechanisms underlying this toxicity are unclear, though disrupted placental functions could play an important role. In this study we examined associations between cadmium concentrations and DNA methylation throughout the placental genome, across two US birth cohorts. We observed cadmium-associated differential methylation, and corresponding methylation-expression associations at genes involved in cellular growth processes and/or immune and inflammatory signaling. This study provides supporting evidence that disrupted placental epigenetic regulation of cellular growth and immune/inflammatory signaling could play a role in cadmium associated reproductive toxicity in human pregnancies.

epidemiology↗