Claudia Chica

Background: B‐cell precursor acute lymphoblastic leukemia (B‐ALL) is a hematologic malignancy characterized by the uncontrolled proliferation of immature B lymphoblasts. Despite significant advancements in treatment, chemoresistance remains a major challenge. Previous studies, including those involving Colombian patient cohorts, have identified a gene signature involving ID1, ID3 , and IGJ , which correlates with poor prognosis; however, the underlying mechanisms remain unclear. This study integrates metabolic profiling with gene expression analysis of ID1, ID3 , and IGJ in patient‐derived lymphoblasts. It explores the role of IGJ overexpression in NALM‐6 cells to assess its potential contribution to chemoresistance. Methods: Bone marrow samples from 33 newly diagnosed B‐ALL patients were analyzed for ID1, ID3 , and IGJ gene expression. Seahorse XF metabolic assays were conducted on 13 patient samples to assess mitochondrial respiration and glycolytic function. Functional studies were performed in the NALM‐6 B‐ALL cell line using CRISPRa‐mediated IGJ overexpression, followed by metabolic and chemoresistance assays using resazurin‐based viability testing with key chemotherapeutic agents. Results: Patient‐derived lymphoblasts exhibited a quiescent metabolic phenotype, with two distinct metabolic subgroups based on oxygen consumption and glycolysis rates. Higher IGJ expression was significantly associated with the glycolytic subgroup and correlated with worse event‐free survival (EFS, p = 0.0179) and overall survival (OS, p = 0.0205). In NALM‐6 cells, IGJ overexpression led to increased metabolic activity and conferred resistance to dexamethasone, cytarabine, doxorubicin, and methotrexate, but not cyclophosphamide. Conclusion: IGJ upregulation promotes metabolic reprogramming and chemoresistance in B‐ALL, suggesting a potential role for IGJ as a biomarker and therapeutic target in overcoming treatment resistance. These findings provide new insights into the metabolic mechanisms underlying B‐ALL progression and highlight IGJ as a candidate for future targeted interventions.

Innate immune memory, also called trained immunity, refers to the ability of innate immune cells to gain memory characteristics after transient stimulation, resulting in a nonspecific modified inflammatory response upon secondary remote challenge. Bronchial epithelial cells (BECs) participate in innate immune defence and are the first cells of the lower respiratory tract to encounter inhaled pathogens. We recently showed that BECs are capable of innate immune memory after preexposure to Pseudomonas aeruginosa flagellin through epigenetic mechanisms. In the present study, we investigated such mechanisms through the modification of chromatin architecture induced by flagellin preexposure that results in subsequent changes of gene expression. By conducting an unsupervised approach to jointly analyse chromatin accessibility and gene expression, we mapped the remodelling of the epigenomic and transcriptomic profiles during the establishment of BECs memory. We identified a Memory regulatory profile induced by flagellin exposure. It includes clusters of upregulated genes related to inflammation that are linked to a sustainable gain in chromatin accessibility and with an increased activity of specific transcription factors (TFs) whose binding may drive this process. In summary, we demonstrated that flagellin exposure induced changes in chromatin condensation in BECs, which sustains the reprogramming of transcriptional patterns.

Background: Innate immune memory, also called trained immunity, refers to the ability of innate immune cells to gain memory characteristics after transient stimulation, resulting in a nonspecific modified inflammatory response upon secondary remote challenge. Bronchial epithelial cells (BECs) participate in innate immune defence and are the first cells of the lower respiratory tract to encounter inhaled pathogens. We recently showed that BECs are capable of innate immune memory after preexposure to Pseudomonas aeruginosa flagellin through epigenetic mechanisms. In the present study, we investigated such mechanisms through the modification of chromatin architecture induced by flagellin preexposure that results in subsequent changes of gene expression. Results: By conducting an unsupervised approach to jointly analyse chromatin accessibility and gene expression, we mapped the remodelling of the epigenomic and transcriptomic profiles during the establishment of BECs memory. We identified a Memory regulatory profile induced by flagellin exposure. It includes clusters of upregulated genes related to inflammation that are linked to a sustainable gain in chromatin accessibility and with an increased activity of specific factors (TFs) whose binding may drive this process. Conclusions: In summary, we demonstrated that flagellin exposure induced changes in chromatin condensation in BECs, which sustains the reprogramming of transcriptional patterns

Cockayne syndrome (CS) and UV‐sensitive syndrome (UVSS) are rare genetic disorders caused by mutation of the DNA repair and multifunctional CSA or CSB protein, but only CS patients display a progeroid and neurodegenerative phenotype, providing a unique conceptual and experimental paradigm. As DNA methylation (DNAm) remodelling is a major ageing marker, we performed genome‐wide analysis of DNAm of fibroblasts from healthy, UVSS and CS individuals. Differential analysis highlighted a CS‐specific epigenomic signature (progeroid‐related; not present in UVSS) enriched in three categories: developmental transcription factors, ion/neurotransmitter membrane transporters and synaptic neuro‐developmental genes. A large fraction of CS‐specific DNAm changes were associated with expression changes in CS samples, including in previously reported post‐mortem cerebella. The progeroid phenotype of CS was further supported by epigenomic hallmarks of ageing: the prediction of DNAm of repetitive elements suggested an hypomethylation of Alu sequences in CS, and the epigenetic clock returned a marked increase in CS biological age respect to healthy and UVSS cells. The epigenomic remodelling of accelerated ageing in CS displayed both commonalities and differences with other progeroid diseases and regular ageing. CS shared DNAm changes with normal ageing more than other progeroid diseases do, and included genes functionally validated for regular ageing. Collectively, our results support the existence of an epigenomic basis of accelerated ageing in CS and unveil new genes and pathways that are potentially associated with the progeroid/degenerative phenotype.

We present ePeak, a Snakemake-based pipeline for the identification and quantification of reproducible peaks from raw ChIP-seq, CUT&RUN and CUT&Tag epigenomic profiling techniques. It also includes a statistical module to perform tailored differential marking and binding analysis with state of the art methods. ePeak streamlines critical steps like the quality assessment of the immunoprecipitation, spike-in calibration and the selection of reproducible peaks between replicates for both narrow and broad peaks. It generates complete reports for data quality control assessment and optimal interpretation of the results. We advocate for a differential analysis that accounts for the biological dynamics of each chromatin factor. Thus, ePeak provides linear and nonlinear methods for normalisation as well as conservative and stringent models for variance estimation and significance testing of the observed marking/binding differences. Using a published ChIP-seq dataset, we show that distinct populations of differentially marked/bound peaks can be identified. We study their dynamics in terms of read coverage and summit position, as well as the expression of the neighbouring genes. We propose that ePeak can be used to measure the richness of the epigenomic landscape underlying a biological process by identifying diverse regulatory regimes.

Virulence of the neonatal pathogen Group B Streptococcus is under the control of the master regulator CovR. Inactivation of CovR is associated with large-scale transcriptome remodeling and impairs almost every step of the interaction between the pathogen and the host. However, transcriptome analyses suggested a plasticity of the CovR signaling pathway in clinical isolates leading to phenotypic heterogeneity in the bacterial population. In this study, we characterized the CovR regulatory network in a strain representative of the CC-17 hypervirulent lineage responsible of the majority of neonatal meningitis. Transcriptome and genome-wide binding analysis reveal the architecture of the CovR network characterized by the direct repression of a large array of virulence-associated genes and the extent of co-regulation at specific loci. Comparative functional analysis of the signaling network links strain-specificities to the regulation of the pan-genome, including the two specific hypervirulent adhesins and horizontally acquired genes, to mutations in CovR-regulated promoters, and to variability in CovR activation by phosphorylation. This regulatory adaptation occurs at the level of genes, promoters, and of CovR itself, and allows to globally reshape the expression of virulence genes. Overall, our results reveal the direct, coordinated, and strain-specific regulation of virulence genes by the master regulator CovR and suggest that the intra-species evolution of the signaling network is as important as the expression of specific virulence factors in the emergence of clone associated with specific diseases.

Cockayne syndrome (CS) and UV-sensitivity syndrome (UVSS) are rare genetic disorders caused by mutation of the DNA repair and chromatin remodelling proteins CSA or CSB, but only CS patients display a progeroid and neurodegenerative phenotype. As epigenetic modifications constitute a well-established hallmark of ageing, we characterized genome-wide DNA methylation (DNAm) of fibroblasts from CS versus UVSS patients and healthy donors. The analysis of differentially methylated positions and regions revealed a CS-specific epigenetic signature, enriched in developmental transcription factors, transmembrane transporters, and cell adhesion factors. The CS-specific signature compared to DNAm changes in other progeroid diseases and regular ageing, identifyied commonalities and differences in epigenetic remodelling. CS shares DNAm changes with normal ageing more than other progeroid diseases do, and according to the methylation clock CS samples show up to 13-fold accelerated ageing. Thus, CS is characterized by a specific epigenomic signature that partially overlaps with and exacerbates DNAm changes occurring in physiological aging. Our results unveil new genes and pathways that are potentially relevant for the progeroid/degenerative CS phenotype.

We present ChIPflow, a Snakemake-based pipeline for epigenomic data from the raw fastq files to the differential analysis. It can be applied to any chromatin factor, e.g. histone modification or transcription factor, which can be profiled with ChIP-seq. ChIPflow streamlines critical steps like the quality assessment of the immunoprecipitation using cross-correlation and the replicate comparison for both narrow and broad peaks. For the differential analysis ChIPflow provides linear and nonlinear methods for normalisation between samples as well as conservative and stringent models for estimating the variance and testing the significance of the observed binding/marking differences. ChIPflow can process in parallel multiple chromatin factors with different experimental designs, number of biological replicates and/or conditions. It also facilitates the specific parametrisation of each dataset allowing both narrow or broad peak calling, as well as comparisons between the conditions using multiple statistical settings. Finally, complete reports are produced at the end of the bioinformatic and the statistical part of the analysis, which facilitate the data quality control and the interpretation of the results. We explored the discriminative power of the statistical settings for the differential analysis, using a published dataset of three histone marks (H3K4me3, H3K27ac and H3K4me1) and two transcription factors (Oct4 and Klf4) profiled with ChIP-seq in two biological conditions (shControl and shUbc9). We show that distinct results are obtained depending on the sources of ChIP-seq variability and the dynamics of the chromatin factor under study. We propose that ChIPflow can be used to measure the richness of the epigenomic landscape underlying a biological process by identifying diverse regulatory regimes and the associated genes sets.

Post-translational modifications of histones are important components of chromatin-level control of genome activity in eukaryotes. In order to clarify the biological function of chromatin marks, classification methods have been developed that partition genomic regions based on their chromatin composition. Spatial enrichment of histone modifications over genes is one of the many epigenomic dimensions that reflect the impact of chromatin dynamics on gene regulation. Using a clustering approach, we have classified genes according to their H3K27me3 and H3K4me3 marking in Arabidopsis leaves and find that multiple spatial profiles with specific functional properties can be distinguished in both cases. In particular, we show that different profiles specify distinct levels of gene expression. In addition, we find that genes with different H3K27me3 profiles can be distinguished by the length of their first intron and that the length of the first exon is an important parameter that shapes the distinct H3K4me3 profiles. Finally, we suggest that profile height could be quantitatively used to estimate the relative abundance of cells in which a gene is marked, and potentially expressed, within a tissue.