Juan Ramón Tejedor

DNA methylation changes accumulate with age through both regulated and stochastic processes, yet the determinants of epigenetic information loss remain poorly defined. Using genome-wide DNA methylation profiles from 1,531 healthy human samples spanning 14 tissues, we quantified epigenetic noise by Shannon entropy and corrected it for cellular and tissue heterogeneity. Adjusted entropy was consistently low in promoters, first exons and CpG islands, and high in CpG-poor and intergenic regions. Cumulative mitotic history showed a stronger association with epigenetic noise than chronological age, explaining most of its variance particularly within CpG-rich regulatory regions. By contrast, age-related, replication-independent effects predominated outside CpG islands and in low-proliferative tissues such as the brain. Moreover, biological age acceleration was largely attributable to cell division in a tissue-specific manner. Collectively, mitotic history emerges as a major determinant of epigenetic noise accumulation across human tissues, while genomic context modulates regional vulnerability to methylation information loss during aging.

KMT2A-rearranged B-cell acute lymphoblastic leukemia (KMT2A-r B-ALL) is an aggressive subtype of leukemia, characterized by high relapse rates, therapy resistance, and poor prognosis. Although CD19-targeted immunotherapies have significantly benefited patients with relapsed/refractory (R/R) disease, relapses remain common and long-term survival is especially poor in KMT2A-r B-ALL patients. We recently identified the membrane-bound proteoglycan NG2 (CSPG4) as direct transcriptional target of KMT2A fusions, with its expression associated with poor prognosis, early relapse, and glucocorticoid resistance in KMT2A-r B-ALL. However, the molecular mechanism underlying the aggressiveness of KMT2A-r B-ALL remains poorly understood. Here, we identify the α4 integrin subunit (ITGA4) and NG2 as a key biological axis contributing to leukemic aggressiveness. NG2 expression promotes proliferation and migration of KMT2A-r B-ALL cells and it is associated with Rho GTPase activity in an ITGA4-dependent manner. In vivo studies using immunodeficient mice demonstrated that ITGA4 and NG2 cooperate to promote leukemia progression as combined genetic ablation of both genes significantly delayed disease onset and prolonged survival. Notably, Natalizumab (NTZ) - an FDA/EMA-approved monoclonal antibody targeting ITGA4 - delayed leukemia progression and potentiated the efficacy of standard-of-care chemotherapy in KMT2A-r B-ALL patient-derived xenograft (PDX) models. Collectively, our findings define a novel ITGA4-NG2 signaling axis that drives the aggressiveness of KMT2A-r B-ALL and support the repurpose of NTZ as an adjuvant therapeutic strategy for this high-risk leukemia subtype.

B-cell acute lymphoblastic leukemia (B-ALL) is the most common pediatric cancer, with long-term overall survival rates of ∼85%. However, B-ALL harboring rearrangements of the MLL gene (also known as KMT2A), referred to as MLLr B-ALL, is common in infants and is associated with poor 5-year survival, relapses, and refractoriness to glucocorticoids (GCs). GCs are an essential part of the treatment backbone for B-ALL, and GC resistance is a major clinical predictor of poor outcome. Elucidating the mechanisms of GC resistance in MLLr B-ALL is, therefore, critical to guide therapeutic strategies that deepen the response after induction therapy. Neuron-glial antigen-2 (NG2) expression is a hallmark of MLLr B-ALL and is minimally expressed in healthy hematopoietic cells. We recently reported that NG2 expression is associated with poor prognosis in MLLr B-ALL. Despite its contribution to MLLr B-ALL pathogenesis, the role of NG2 in MLLr-mediated leukemogenesis/chemoresistance remains elusive. Here, we show that NG2 is an epigenetically regulated direct target gene of the leukemic MLL-ALF transcription elongation factor 4 (AF4) fusion protein. NG2 negatively regulates the expression of the GC receptor nuclear receptor subfamily 3 group C member 1 (NR3C1) and confers GC resistance to MLLr B-ALL cells. Mechanistically, NG2 interacts with FLT3 to render ligand-independent activation of FLT3 signaling (a hallmark of MLLr B-ALL) and downregulation of NR3C1 via activating protein-1 (AP-1)–mediated transrepression. Collectively, our study elucidates the role of NG2 in GC resistance in MLLr B-ALL through FLT3/AP-1–mediated downregulation of NR3C1, providing novel therapeutic avenues for MLLr B-ALL.

Background: Hypertrophic cardiomyopathy is an autosomal dominant cardiac disease. The mechanisms that determine its variable expressivity are poorly understood. Epigenetics could play a crucial role in bridging the gap between genotype and phenotype by orchestrating the interplay between the environment and the genome regulation. In this study we aimed to establish a possible correlation between the peripheral blood DNA methylation patterns and left ventricular hypertrophy severity in patients with hypertrophic cardiomyopathy, evaluating the potential impact of lifestyle variables and providing a biological context to the observed changes. Methods and Results: Methylation data were obtained from peripheral blood samples (Infinium MethylationEPIC BeadChip arrays). We employed multiple pair‐matched models to extract genomic positions whose methylation correlates with the degree of left ventricular hypertrophy in 3 monozygotic twin pairs carrying the same founder pathogenic variant ( MYBPC3 p.Gly263Ter). This model enables the isolation of the environmental influence, beyond age, on DNA methylation changes by removing the genetic background. Our results revealed a more anxious personality among more severely affected individuals. We identified 56 differentially methylated positions that exhibited moderate, proportional changes in methylation associated with left ventricular hypertrophy. These differentially methylated positions were enriched in regions regulated by repressor histone marks and tended to cluster at genes involved in left ventricular hypertrophy development, such as HOXA5 , TRPC3 , UCN3 , or PLSCR2 , suggesting that changes in peripheral blood may reflect myocardial alterations. Conclusions: We present a unique pair‐matched model, based on 3 monozygotic twin pairs carrying the same founder pathogenic variant and different phenotypes. This study provides further evidence of the pivotal role of epigenetics in hypertrophic cardiomyopathy variable expressivity.

Aging is a multifactorial biological process resulting in physiological and cellular decline. However, our understanding of age-related changes in 3D genome organization and the effect of external interventions on this process, remains limited. Here we describe alterations in the landscape of the 3D chromatin interactome upon aging, utilizing the low input Promoter Capture Hi-C (liCHi-C) technique with hippocampal neurons. We integrated liCHi-C data with RNA-seq data to identify functional implications. Furthermore, we assessed the effect of exposure to environmental enrichment (EE). Remarkably, our results demonstrated an age- dependent modulation of promoter interactions and expression with EE, with aging-like changes induced in young mice upon EE, likely associated with early brain maturation; while age-related alterations were reverted in old mice, leading to a partial rejuvenation of aged mouse hippocampi. These findings revealed a dynamic behaviour of the neuronal 3D chromatin structure over time, which can be modulated by external interventions.

Loss of epigenetic information has been proposed as a potential driver of mammalian aging. However, its contribution to the well-documented variation in lifespan estimates among mammals remains to be elucidated. In this study, we examined DNA methylation entropy patterns at evolutionarily conserved CpG sites across multiple mammalian species to quantify age-associated epigenetic information loss. We found that longer-lived species tend to accumulate fewer CpGs exhibiting increased methylation noise over time, irrespective of whether these changes arise from hyper- or hypomethylation mechanisms. Importantly, the rate of epigenetic entropy gain declines in a linear fashion with species’ maximum lifespan, pointing to the existence of a universal constraint on mammalian longevity, estimated to lie in the vicinity of 220 years. We further demonstrated that this relationship and its associated limit were independent of species and sample selection, as well as phylogenetic relatedness, and remained robust across different scenarios of lifespan estimation uncertainty. Collectively, this work highlights the maintenance of epigenetic information as a key factor in explaining lifespan differences among species and proposes a universal maximum limit to natural mammalian longevity.

The combination of a nucleic acid amplification method through multiplexed RCA, coupled with signal amplification mediated by FokI-assisted digestion of dumbbell-like oligonucleotides, enhances the detection of multiple human respiratory viruses.

Cellular ontogeny and MLL breakpoint site influence the capacity of MLL-edited CD34+ hematopoietic cells to initiate and recapitulate infant patients' features in pro–B-cell acute lymphoblastic leukemia (B-ALL). We provide key insights into the leukemogenic determinants of MLL-AF4+ infant B-ALL.

Aging and cancer are clearly associated processes, at both the epidemiological and molecular level. Epigenetic mechanisms are good candidates to explain the molecular links between the two phenomena, but recent reports have also revealed considerable differences, particularly regarding the loss of DNA methylation in the two processes. The large‐scale generation and availability of genome‐wide epigenetic data now permits systematic studies to be undertaken which may help clarify the similarities and differences between aging and cancer epigenetic alterations. In addition, the development of epigenetic clocks provides a new dimension in which to investigate diseases at the molecular level. Here, we examine current and future questions about the roles of DNA methylation mechanisms as causal factors in the processes of aging and cancer so that we may better understand if and how aging‐associated epigenetic alterations lead to tumorigenesis. It seems certain that comprehending the molecular mechanisms underlying epigenetic clocks, especially with regard to somatic stem cell aging, combined with applying single‐cell epigenetic‐age profiling technologies to aging and cancer cohorts, and the integration of existing and upcoming epigenetic evidence within the genetic damage models of aging will prove to be crucial to improving understanding of these two interrelated phenomena.