Epigenomes

Background/Objectives: Atrial fibrillation (AF) is currently the most common arrhythmia worldwide, and it is linked to increased mortality and morbidity, hence the need for a better clinical stratification of AF patients. Histone complexes or nucleosomes, released into the blood circulation, are found elevated in acute conditions such as stroke, trauma, and sepsis. The aim of this pilot single-centre study was to assess whether circulating histone levels could be used for diagnostic purposes in patients with AF. Methods: A total of 40 patients, well characterised for their biochemical and clinical characteristics, were recruited from outpatient clinics. Patients were randomly recruited into two groups (n = 20 per group), i.e., persistent AF and hypertensive controls. A multi-channel flow imaging methodology based on ImageStreamX was used with a well-optimised protocol to image and quantify five individual histones (H2A, H2B, H3, H4, and macroH2A1.1) together with the dimers (H2A/H2B, and H3/H4). Results: In the AF groups, plasma levels of histone dimers H2A/H2B and H3/H4 were elevated compared to hypertensive controls, 1.8% vs. 1.06% (p-value = 0.03). H2A/H2B dimer levels were increased in AF patients irrespective of gender, smoking status, diabetes, and pharmacological therapy. In the overall population, an inverse correlation between H2A and BMI was detected. Conclusions: Our pilot study, although limited in sample size, suggests that circulating histone complexes may be epigenetic sentinels for AF, offering mechanistic insights while addressing unmet needs in risk stratification.

Background/Objectives: High-risk, low-frequency incidents such as building collapses and large chemical fires can result in acute, high-dose exposures to toxic agents for first responders and the surrounding community. While these exposures may last for hours to days, their contribution to firefighters’ risks for cancer and other diseases is relatively unknown. In February 2023, a freight train transporting chemicals derailed and caught fire in East Palestine, Ohio, US. More than 350 firefighters, primarily volunteer, responded to the incident. In this cross-sectional study, we evaluated epigenetic markers of toxicity in responding firefighters. We hypothesized that exposures from responding to the train derailment would alter the expression of microRNAs (miRNAs) linked to carcinogenesis. Methods: We enrolled 62 responding firefighters and a comparison group of 26 firefighters from the same region who did not respond to the incident. We measured the relative expression of 800 miRNAs in blood samples using the nCounter Human v3 miRNA expression panel. We compared the expression of miRNA between exposure groups in negative binomial regression models, adjusting for potential confounders. Results: At a false discover rate cut-off of 5% (q-value < 0.05), 16 miRNAs had significantly higher expression and one significantly lower among firefighters that responded to the incident. Top disease-related pathways in which these miRNAs were enriched included those relevant to neurodegenerative diseases, vascular disease, and multiple cancer sites. Conclusions: Overall, results suggest responding to one large incident can have non-transient impacts on miRNA expression. Whether this translates into longer-term health risks or adaptive responses to exposures is unclear.

In the filamentous fungus Neurospora crassa, a gene not having a pairing partner during meiosis is seen as a potential intruder and is targeted by a mechanism called meiotic silencing by unpaired DNA (MSUD). MSUD employs core RNA interference (RNAi) components such as the SMS-2 Argonaute, which uses small interfering RNAs (siRNAs) as guides to seek out mRNAs from unpaired genes for silencing. In Drosophila melanogaster, the heat shock protein 70 (Hsp70) chaperone system facilitates the conformational activation of an Argonaute and allows it to load siRNAs. Here, our results demonstrate that an Hsp70 protein in Neurospora interacts with SMS-2 and mediates the silencing of unpaired genes.