Biology subjects

Thanos, D.

Publications and source records attributed to Thanos, D..

5 recordsLinked to original sources

bioRxiv2025

Repurposed macroH2A Chromatin Landscapes Guide Cellular Reprogramming

Cellular reprogramming converts differentiated cells into a pluripotent state through extensive chromatin remodeling. The histone variant macroH2A has classically viewed as an epigenetic barrier stabilizing somatic identity and restricting pluripotency gene activation. Here, we show that during reprogramming, macroH2A1 nucleosomes undergo functional repurposing. Early in the process, mH2A1 nucleosomes act as a barrier to cellular plasticity, but later facilitate the establishment and maintenance of pluripotency by reshaping the epigenetic landscape. High-resolution chromatin profiling reveals that mH2A1.2 nucleosomes undergo rapid, large-scale repositioning, dissociating from promoters and reassembling [~]30 bp away, frequently near NRF-1 binding sites. This repositioning occludes E2F4 binding, relieving cell-cycle arrest thereby enabling reprogramming. Likewise, mH2A1.1 nucleosomes display extensive mobility that culminates in deposition at pluripotency genes in ESCs, where they sustain their expression by assembling promoter transcriptional hubs. In this later role, mH2A1.1 functions as a chromatin bookmark stabilizing the Nanog, Sox2, and Oct4 network. These findings suggest that mH2A1 nucleosomal mobility underlines its context-dependent functional repurposing from reprogramming inhibitor to facilitator, illustrating how chromatin components evolve dynamic roles to coordinate cell-state transitions.

molecular biology↗

bioRxiv2025

Immune cell senescence drives responsiveness to immunotherapy in melanoma

AbstractBackground: Immunotherapy has significantly improved cancer treatment. However, it is not effective in all cancer patients, rendering the need to further delineate the differences among responders and non-responders at the molecular and cellular level. Unresponsiveness to immunotherapy has been attributed to dysfunctional immune cell states such as T-cell exhaustion and anergy, whereas the contribution of cellular senescence remains elusive. Herein, we have investigated the role of immune cell senescence in the response to checkpoint inhibitors in melanomas where these immunotherapies are applied as a first line treatment. Methods: Two senescence detecting complementary approaches were utilized in a case control study we conducted. First, we implemented a senescence molecular signature we developed, termed "SeneVick" retrospectively in a single cell RNA-seq dataset from melanoma patients who received immunotherapy. Prior to this analysis, the signature was extensively validated in a variety of cell/tissue contexts, senescence types and species. Second, cellular senescence was assessed via an established experimental algorithmic approach in circulating immune cells of an analogous melanoma clinical cohort. Results: Melanoma patients who did not respond to immunotherapy exhibited increased cellular senescence in their CD8+ T-cells, CD4+ T-cells, B-cells and NK cells compared to responders. This phenomenon was independent of patients age and not an outcome of immunotherapy, in contrast to conventional anti-cancer treatments. Interestingly, alterations of cell-cell interactions among the immune sub-populations in non-responders compared to responders were identified, suggesting the involvement of immune cell senescence in defective immune responses and treatment failure. Conclusion: Overall, our findings support cellular senescence of the immune cell compartment within the TME, as a potent determinant of the response to immunotherapy and pave the way for strategies targeting immune cell senescence, as promising approaches to improve the outcome of such interventions.

immunology↗

bioRxiv2024

Polyunsaturated fatty acid-derived lipid mediator networks characterize COVID-19 severity and risk for critical illness

Severe COVID-19, caused by SARS-CoV-2 infection, is characterized by excessive inflammation leading to the development of pneumonia and acute respiratory distress syndrome. Bioactive lipid mediators (LMs) derived from {omega}6 and {omega}3 polyunsaturated fatty acids are central to the regulation of inflammation, controlling both its initiation and resolution. Still, their role in COVID-19 remains underexplored. By employing a holistic approach involving the analysis of white blood cell transcriptomes, targeted lipidomics, cytokine and immune cell profiling, across the spectrum of disease severity groups, including mild non-hospitalized patients and healthy individuals, we now show that LM networks are profoundly altered in COVID-19, correlate with inflammatory patterns, and stratify patients according to disease severity. Central to this are CYP450-derived LMs such as 20-HETE, lipid peroxidation metabolites such as iPF2a-VI, and lipoxygenase-derived LMs such as 12-HETE, all of which are major vasoactive mediators of inflammation. Among them, 20-HETE appears to be a promising prognostic biomarker for ICU admission and a potential therapeutic target for severe COVID-19 disease. Our study thus underscores the significance of LM networks in COVID-19 pathophysiology and sheds light into the broader mechanisms driving viral pneumonia in humans. O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=158 SRC="FIGDIR/small/610123v1_ufig1.gif" ALT="Figure 1"> View larger version (69K): org.highwire.dtl.DTLVardef@6e406dorg.highwire.dtl.DTLVardef@47c9deorg.highwire.dtl.DTLVardef@1162488org.highwire.dtl.DTLVardef@b86ba3_HPS_FORMAT_FIGEXP M_FIG C_FIG

immunology↗

bioRxiv2023

Senescent cells in Giant Cell Arteritis have inflammatory phenotype participating in tissue injury via IL-6 dependent pathways

ObjectivesAge is the strongest risk factor of Giant Cell Arteritis (GCA), implying a possible pathogenetic role of cellular senescence. To address this question, we applied an established senescence specific multi-marker algorithm in tissue artery biopsies (TABs) of GCA patients. MethodsSeventy five positive TABs from GCA patients and 22 negative from patients with Polymyalgia Rheumatica (PMR) were retrospectively retrieved and analyzed. Senescent cells and their histologic origin were identified with specific cellular markers; IL-6 and MMP-9 were investigated as components of the senescent associated secretory phenotype (SASP) by triple co-staining. GCA or PMR artery culture supernatants were applied to primary skin fibroblasts with or without IL-6 blocking agent to explore the induction of IL-6 associated cellular senescence. ResultsSenescent cells were mainly present in GCA arteries at higher proportion compared to PMR (9.50% vs 2.66% respectively, p<0.0001) and were mainly originated from fibroblasts, macrophages and endothelial cells. IL-6 was expressed by senescent fibroblasts and macrophages while MMP-9 by fibroblasts only. IL-6 positive senescent cells were associated with the extension of vascular inflammation (adventitial limited disease vs transmural inflammation: 10.02% vs 4.37% respectively, p<0.0001). GCA but not PMR artery culture supernatant could induce IL-6-associated senescence that was partially inhibited by IL-6 blockade. ConclusionsSenescent cells with inflammatory phenotype are present in GCA arteries and are associated with the tissue inflammatory bulk. These findings might suggest a potential implication in disease pathogenesis by perpetuating inflammation and affecting vascular remodeling via IL-6 dependent mechanisms.

cell biology↗

bioRxiv2022

Return of the Tbx5; lineage-tracing reveals ventricular cardiomyocyte-like precursors in the injured adult mammalian heart

The single curative measure for heart failure patients is total heart transplantation, which is limited due to a shortage of donors, the need for immunosuppression and economic costs. Therefore, there is an urgent unmet need for identifying cell populations capable of cardiac regeneration that we will be able to trace and monitor. Injury to the adult mammalian cardiac muscle, often leads to a heart attack through the irreversible loss of a large number of cardiomyocytes, due to an idle regenerative capability. Recent reports in zebrafish indicate that Tbx5a is a vital transcription factor for cardiomyocyte regeneration. Preclinical data underscore the cardioprotective role of Tbx5 upon heart failure. Data from our earlier murine developmental studies have pinpointed a prominent unipotent Tbx5-expressing embryonic cardiac precursor cell population able to form cardiomyocytes, in vivo, in vitro and ex vivo. Using a developmental approach to an adult heart injury model and by employing a lineage-tracing mouse model as well as the use of single-cell RNA-seq technology, we identify a Tbx5-expressing ventricular cardiomyocyte-like precursor population, in the injured adult mammalian heart. The transcriptional profile of that precursor cell population is closer to that of neonatal than embryonic cardiomyocyte precursors. Tbx5, a cardinal cardiac development transcription factor, lies in the centre of a ventricular adult precursor cell population, which seems to be affected by neurohormonal spatiotemporal cues. The identification of a Tbx5-specific cardiomyocyte precursor-like cell population, which is capable of dedifferentiating and potentially deploying a cardiomyocyte regenerative program, provides a clear target cell population for translationally-relevant heart interventional studies.

cell biology↗