Biology subjects

Pepin, M. E.

Publications and source records attributed to Pepin, M. E..

5 recordsLinked to original sources

bioRxiv2026

Aortic valve stenosis promotes pathological shear stress-dependent epigenomic dysregulation in circulating T cells.

BackgroundCalcific aortic valve stenosis (AVS) is the most prevalent valvular heart disease in Western adults, yet no disease-modifying therapy exists. High shear stress (HSS) generated by progressive valvular obstruction drives endothelial injury and immune-mediated inflammation, but the contribution of circulating T cells to AVS pathogenesis remains poorly defined. ObjectivesWe tested whether chronic HSS corresponds with epigenomic reprogramming of peripheral T cells proportionate with hemodynamic severity to yield a clinically informative proxy of disease. MethodsA prospective cohort of 70 participants was recruited for peripheral blood sampling, including 34 with severe symptomatic AVS (aortic valve area <1.0 cm2, mean gradient [≥]40 mmHg) scheduled for transcatheter aortic valve implantation and 36 age- and sex-matched controls. Peripheral T cells were isolated and profiled by genome-wide CpG methylation (Illumina MethylationEPIC) and RNA-sequencing. To test whether HSS directly activates inflammatory signaling, Jurkat T cells were exposed to 20 dyn/cm2 HSS via parallel-plate microfluidic chamber and concomitant CD3/CD28 stimulation, followed by assessment of NFAT nuclear translocation and NFAT target gene expression. ResultsUnsupervised clustering of the 5,000 most-variable CpG loci resolved an epigenomic axis segregating AVS from control T cells (PC1, 15.8% variance explained; P = 3.9x10-6). Multivariable-adjusted analysis identified 3,950 differentially methylated positions (1,889 hyper-, 2,061 hypo-methylated), enriched in promoter-associated CpG islands implicating aortic valve morphogenesis (P = 6.0 x 10-10) and cell-cell adhesion pathways (P = 9.5 x 10-5). Multi-omics factor analysis isolated a latent factor that independently associated with AVS (adjusted P = 1.8x10-3; AUC = 0.79), enriched for chemokine receptor binding and TNF-family signaling, and correlated with canonical HSS-responsive transcripts, consistent with a T cell-mediated shear stress activation. An 18-CpG elastic-net methylation risk score discriminated AVS from controls (AUC = 0.89) and independently predicted hemodynamic severity ({beta} = 7.05 mmHg/SD, 95% CI 2.31-11.79). HSS augmented NFAT nuclear translocation in CD3/CD28-activated Jurkat T cells and induced NFAT-responsive inflammatory transcripts. ConclusionsSevere AVS is associated with promoter-enriched epigenomic remodeling of circulating T cells that converges on hemodynamic stress-dependent inflammatory programs. An 18-CpG methylation risk score outperforms clinical covariates and tracks hemodynamic severity, establishing peripheral T cell DNA methylation as a molecular corollary of AVS.

molecular biology↗

bioRxiv2025

CAMK2-NR4A1 signaling initiates metabolic substrate switching to induce heart failure with reduced ejection fraction

Heart failure with reduced ejection fraction (HFrEF) is marked by a shift in cardiac energy metabolism from fatty acid oxidation to glucose utilization. This "fuel switch" promotes accumulation of glucose byproducts that modify calcium-handling proteins and impair cardiac function, yet the initiating signals remain unclear. We identify Ca2+/calmodulin-dependent protein kinase II (CAMK2) as an upstream regulator that triggers pathological substrate switching leading to cardiac systolic dysfunction. Dynamic [18F]FDG-PET imaging showed a six-fold increase in myocardial glucose uptake after pressure overload in control mice, but not in cardiomyocyte-specific Camk2d/Camk2g double knockouts (cDKO), even before functional decline. cDKO hearts retained lipid reserves, indicating preserved fatty acid metabolism. Transcriptomics revealed strong CAMK2-dependent induction of Nr4a1 and early repression of genes for fatty acid uptake and {beta}-oxidation preceding upregulation of genes for glucose utilization. Cardiomyocyte-specific Nr4a1 knockout mice closely mimicked the metabolic protection seen in cDKO, while NR4A1 overexpression in human iPSC-derived cardiomyocytes suppressed fatty acid metabolism. NR4A1 directly bound and repressed the FATP1 (Slc27a1) promoter, thereby secondarily enhancing glucose utilization. Together, these findings define a CAMK2-NR4A1 signaling axis that drives lipid depletion and metabolic remodeling, establishing it as a causal mechanism linking energy substrate switching to HFrEF.

physiology↗

bioRxiv2025

Somatic Hdac4-902fs mutations lead to loss of HDAC4 function through nonsense-mediated mRNA degradation

Histone deacetylases (HDACs) are essential chromatin regulators and are involved in the regulation of gene expression by removing acetyl groups from histone and non-histone proteins. Histone deacetylase 4 (HDAC4) is known to regulate the process of endochondral ossification in mice by non-enzymatic repression of the activity of the RUNX2 transcription factor (TF) and to control cardiac metabolism in physiological stress situations. In this study, we examined the function of somatic HDAC4-902 frameshift (fs) mutations that are frequently observed in gastric and colon adenocarcinoma patients. Whether these mutations lead to a gain- or a loss-of-function is currently unknown. Here we generated a murine model bearing a germline HDAC4-methionine (M) amino acid (AA) 902-to-histidine (H) frameshift (M902Hfs) mutation. HDAC4-M902Hfs mice phenocopied HDAC4 null mice and present with premature ossification and early postnatal death. Mechanistically, we found that the HDAC4-M902Hfs mutation induced nonsense-mediated mRNA decay, resulting in loss of HDAC4 protein. This loss-of-function (LOF) effect was further supported by increased mRNA and protein expression of runt-related transcription factor-2 (RUNX2) and reduced class IIa HDAC enzymatic activity, indicating that HDAC4 contributes significantly to endogenous class IIa HDAC activity. Patient-derived data suggest that the HDAC4-902fs mutation is associated with reduced mRNA expression of HDAC4. In conclusion, our study identify that HDAC4-902fs mutation is a loss-of-function mutation, but raises the new question whether the loss of non-enzymatic mechanisms or the reduction in class IIa HDAC activity contributes to tumor progression.

cancer biology↗

bioRxiv2023

Genetic Loss of Nicotinamide Nucleotide Transhydrogenase Prevents from Cardiometabolic Heart Failure with Preserved Ejection Fraction

RationaleHeart failure with preserved ejection fraction (HFpEF) represents a common clinical endpoint of cardiometabolic diseases which impair myocardial diastolic relaxation. Although myocardial redox perturbations are known to accompany HFpEF, the specific role of mitochondrial oxidative stress has not been demonstrated yet. ObjectiveBased on an observation that C57BL6/N - but not C57BL6/J - mice develop diastolic dysfunction when provided an ad libitum high-fat and 0.5% N({omega})-nitro-L-arginine methyl ester (HFD+L-NAME) diet, we conducted a multi-cohort murine study to determine whether the loss of Nicotinamide Nucleotide Transhydrogenase (NNT), a mitochondrial transhydrogenase that couples NADPH:NADP+ to NADH:NAD+ homeostasis, protects mice from developing cardiometabolic alterations. Methods and ResultsTwo cohorts of 12-week-old male and female mice possessing wild-type (Nnt+/+) or deleted (Nnt-/-) NNT were challenged by HFD+L-NAME for 9 weeks (n = 6-10). Male Nnt+/+ mice developed obesity (23.2% {Delta}, P = 0.003), arterial hypertension (24 {+/-} 5 {Delta} mmHg, P = 0.023), impaired glucose tolerance (P = 0.006), and reduced maximal treadmill running distance (-172 {+/-} 73.1 {Delta} m, P = 0.006) following 9 weeks HFD+L-NAME, whereas male Nnt-/- mice did not. Female mice were protected from cardiometabolic dysfunction regardless of Nnt genotype. Cardiac functional and morphologic characterization revealed similar NNT-dependent and sex-specific increases in E/e (42.8 vs. 21.5, P < 0.001) and E/A (2.3 vs 1.4, P = 0.007) ratios, diastolic stiffness (0.09 vs 0.04 mmHg/L, P = 0.02), and myocardial fibrosis (P = 0.02). Unsupervised transcriptomic analysis identified distinct genetic and dietary signatures, wherein Nnt+/+ exhibited disproportionate perturbations in various mitochondrial oxidative pathways following HFD+L-NAME. Our search for putative transcriptional regulators identified NNT-dependent suppression of NAD+ dependent deacetylase Sirt3. ConclusionsTaken together, these observations support that the genetic disruption of Nnt protects against both cardiac and metabolic consequences of HFD+L-NAME, thus highlighting a novel etiology-specific avenue for HFpEF therapeutics.

physiology↗

bioRxiv2018

Prolactin Receptor Signaling Regulates a Pregnancy-Specific Transcriptional Program in Mouse Islets

Pancreatic {beta}-cells undergo profound hyperplasia during pregnancy to maintain maternal euglycemia. Failure to reprogram {beta}-cells into a more replicative state has been found to underlie susceptibility to gestational diabetes mellitus (GDM). We recently identified a requirement for prolactin receptor (PRLR) signaling in the metabolic adaptations to pregnancy, where mice lacking {beta}-cell PRLR ({beta}PRLRKO) exhibit a metabolic phenotype consistent with GDM. However, the underlying transcriptional program that is responsible for the PRLR-dependent metabolic adaptations during gestation remains incompletely understood. To identify PRLR signaling gene regulatory networks and target genes within {beta}-cells during pregnancy, we performed a transcriptomic analysis of pancreatic islets isolated from either {beta}PRLRKO mice or littermate controls in late gestation. Gene set enrichment analysis identified Forkhead box protein M1 (Foxm1) and polycomb repressor complex 2 (PRC2) subunits, Suz12 and Ezh2, as novel candidate regulators of PRLR-dependent {beta}-cell adaptation. GO-term pathway enrichment revealed both established and novel PRLR signaling target genes that together describe a state of increased cellular metabolism and/or proliferation. In contrast to the requirement for {beta}-cell PRLR signaling in maintaining euglycemia during pregnancy, PRLR target genes were not induced following high-fat-diet feeding. Altogether, the current study expands our understanding of which transcriptional regulators and networks mediate gene expression required for islet adaptation during pregnancy. The current work also supports the presence of pregnancy-specific adaptive mechanisms distinct from those activated by nutritional stress.

bioinformatics↗