Biology subjects

Mieczkowski, J.

Publications and source records attributed to Mieczkowski, J..

10 recordsLinked to original sources

bioRxiv2026

α-Synuclein impairs mitochondrial function and alters cryptochrome regulation in the substantia nigra

Dopaminergic neurons in the substantia nigra pars compacta are key targets of -synuclein pathology and neurodegeneration in Parkinson's disease (PD). It is thought that pathological accumulation of -synuclein significantly contributes to nigral neuronal dysfunction and ensuing neuronal demise. In this study, we further assessed this possibility and interrogated the role of -synuclein burden in compromising neuronal function and altering physiological neuronal pathways. In particular, we focused on nigral mitochondrial impairment and disruption of circadian regulatory pathways triggered by sustained -synuclein expression. Using an in vivo AAV-mediated model, we show that -synuclein accumulation over a period of 12 weeks is associated with mitochondrial complex I and IV deficits and leads to dopaminergic cell loss. Proximity ligation assays revealed association of both total and phosphorylated -synuclein with mitochondrial proteins at a time (between 4 and 12 weeks) that paralleled the development of mitochondrial dysfunction. Spatial transcriptomic analysis of the substantia nigra identified coordinated alterations in genes involved in mitochondrial, metabolic, and circadian pathways, including increased expression of circadian-associated genes such as Nr1d1, Nr1d2, Cry2, Arntl2, and Csnk1e. At the protein level, -synuclein overexpression was associated with a differential shift in cryptochrome protein expression, characterized by reduced CRY1 and increased CRY2. Data provide evidence of a specific window of time during which sustained -synuclein burden results in direct -synuclein-mitochondria interactions and nigral mitochondrial damage. During the same time period, a specific remodeling of molecular clock components occurs, providing a potential new mechanism contributing to metabolic and mitochondrial dysregulations and, ultimately, neuronal injury and degeneration.

neuroscience↗

bioRxiv2026

Spatial Transcriptomics of TNBC tumours and corresponding lymph node metastasis reveals immune hubs driven by TNF/NF-κB signalling of TMSB4X and CD74 expressing cells.

PurposeLymph node metastasis is a critical prognostic factor in triple-negative breast cancer (TNBC), but the spatial organization of signalling networks driving metastatic colonization and persistence remains poorly defined. Understanding these networks may reveal therapeutic vulnerabilities in metastatic TNBC. MethodsWe applied Visium spatial transcriptomics to paired primary tumours and lymph node metastases from four TNBC patients. Spatial gene expression profiles were analysed using trajectory inference, cell-type deconvolution, and cell-cell communication mapping. Results were validated in independent single-cell RNA sequencing datasets from TNBC tumours and lymph node metastases. ResultsTMSB4X and CD74 emerged as key drivers of metastasis-associated transcriptional programs, defining spatially distinct immune communication hubs enriched in myeloid, stromal, and endothelial cells. These hubs preferentially activated NF-{kappa}B/TNF signalling alongside PI3K-Akt and Rap1 pathways. In primary tumours, NF-{kappa}B/TNF signalling was confined to localized immune hubs, whereas lymph node metastases exhibited widespread signalling across cellular compartments with additional IL-1 pathway activation. This spatial rewiring coincided with endothelial cells assuming central coordinating roles in metastatic lesions. Independent validation confirmed myeloid-endothelial crosstalk as a conserved feature of TNBC, with TMSB4X-CD74 programs enriched in clinically relevant immune and vascular subpopulations. ConclusionTNBC lymph node metastases display spatially expanded inflammatory networks centred on TMSB4X-CD74 immune hubs. Metastatic progression involves coordinated myeloid-endothelial signalling, suggesting these pathways as potential biomarkers and therapeutic targets. Disrupting inflammatory and vascular communication networks may offer a strategy to prevent metastatic persistence and overcome therapy resistance in TNBC.

molecular biology↗

bioRxiv2024

p53 Regulates Nuclear Architecture to Reduce Carcinogen Sensitivity and Mutagenic Potential

The p53 tumor suppressor is an indispensable regulator of DNA damage responses that accelerates carcinogenesis when mutated. In this report, we uncover a new mechanism by which p53 maintains genomic integrity in the absence of canonical DNA damage response activation. Specifically, loss of p53 dramatically alters chromatin structure at the nuclear periphery, allowing increased transmission of an environmental carcinogen, ultraviolet (UV) radiation, into the nucleus. Genome-wide mapping of UV-induced DNA lesions in p53-deficient primary cells reveals elevated lesion abundance in regions corresponding to locations of high mutation burden in malignant melanomas. These findings uncover a novel role of p53 in the suppression of mutations that contribute to cancer and highlight the critical influence of nuclear architecture in regulating sensitivity to carcinogens. One-Sentence SummaryThe p53 tumor suppressor reduces carcinogen sensitivity and mutagenic potential by maintaining nuclear architecture.

cancer biology↗

bioRxiv2024

Hypoxic stress dysregulates functions of glioma-associated myeloid cells through epigenomic and transcriptional programs

Hypoxia rapidly alters gene expression to allow cellular adaptation to challenging conditions and support tumour growth. Hypoxia also affects the chromatin structure by modifications of histones and DNA methylation. Glioblastoma (GBM) is an aggressive, deadly primary brain tumour for which there is no effective treatment. The tumour microenvironment of GBM is highly heterogeneous, with infiltration of glioma-associated microglia and macrophages (GAMs) and the presence of necrotic, hypoxic regions which significantly impair effectiveness of therapies. The mechanisms through which hypoxia alters the tumour microenvironment and regulates functions of infiltrating immune cells remain poorly understood. Here, we show that hypoxia modulates the expression of myeloid markers in distinct ways: upregulates the expression of monocytic marker Lgals3 and downregulates the microglial markers P2ry12 and Tmem119 in microglial and monocytic GAMs in vitro and in vivo. Underlying genome-wide hypoxia-dependent transcriptomic changes in microglial cells were identified using microglia-glioma co-cultures and validated in human and mouse GBM single- cell transcriptomics datasets. Numerous GAM subtype markers are dysregulated in response to hypoxic stress due to associated changes in chromatin accessibility, as determined using ATACseq. While hypoxia alone drives a decrease of the overall chromatin accessibility at gene promoters, the exposure to glioma cells under hypoxic conditions leads to both increases and decreases of chromatin accessibility at promoter regions in microglial cells. Hypoxia downregulates the chromatin accessibility at the regions enriched in motifs for transcription factors known as master regulators of microglial cell identity and function, including SPI1 or IRF8. Overall, our results highlight the importance of hypoxic stress as a strong intratumoral regulator of myeloid cell functions, which adds a new dimension to the characterisation of particular GAM subpopulations.

cancer biology↗

bioRxiv2024

Prelude to Malignancy: A Gene Expression Signature in Normal Mammary Gland from Breast Cancer Patients Suggests Pre-tumorous Alterations and Is Associated with Adverse Outcomes

Despite advances in early detection and treatment strategies, breast cancer recurrence and mortality remain a significant health issue. Recent insights suggest the prognostic potential of microscopically healthy mammary gland, in the vicinity of the breast lesion. Nonetheless, a comprehensive understanding of the gene expression profiles in these tissues and their relationship to patient outcomes is still missing. Furthermore, the increasing trend towards breast-conserving surgery may inadvertently lead to the retention of existing cancer-predisposing mutations within the normal mammary gland. This study assessed the transcriptomic profiles of 242 samples from 83 breast cancer patients with unfavorable outcomes, including paired uninvolved mammary gland samples collected at varying distances from primary lesions. As a reference, control samples from 53 mammoplasty individuals without cancer history were studied. A custom panel of 634 genes linked to breast cancer progression and metastasis was employed for expression profiling, followed by whole-transcriptome verification experiments and statistical analyses to discern molecular signatures and their clinical relevance. A distinct gene expression signature was identified in uninvolved mammary gland samples, featuring key cellular components encoding keratins, CDH1, CDH3, EPCAM cell adhesion proteins, matrix metallopeptidases, oncogenes, tumor suppressors, along with crucial genes (FOXA1, RAB25, NRG1, SPDEF, TRIM29, and GABRP) having dual roles in cancer. Enrichment analyses revealed disruptions in epithelial integrity, cell adhesion, and estrogen signaling. This signature, named KAOS for Keratin-Adhesion-Oncogenes-Suppressors, was significantly associated with reduced tumor size but increased mortality rates. Integrating molecular assessment of non-malignant mammary tissue into disease management could enhance survival prediction and facilitate personalized patient care.

genomics↗

bioRxiv2023

H2A.Z histone variants facilitate HDACi-dependent removal of H3.3K27M mutant protein in paediatric high-grade glioma cells

Diffuse intrinsic pontine gliomas (DIPG) are deadly paediatric brain tumours, non-resectable due to brainstem localisation and diffusive growth. Patients with DIPG have a dismal prognosis of 9-12 months of survival with no effective therapy. Over 80% of DIPGs harbour a mutation in histone 3 (H3.3 or H3.1) resulting in a lysine to methionine substitution (H3K27M). H3K27M causes global epigenetic alterations (a loss of H3K27 trimethylation and an increase in H3K27 acetylation) resulting in aberrant gene expression. To date, no therapeutic strategy exists to suppress the levels of oncogenic H3K27M. We show that pan-HDAC inhibitors (HDACi) lead to the temporary but significant reduction in the H3.3K27M protein (up to 80%) in multiple glioma cell lines expressing the H3.3K27M histone variant, without changes in the H3F3A mRNA expression. The H3.3K27M occupancy at the chromatin is greatly reduced upon HDACi (SB939) treatment, as shown by ChIPseq analysis. H3.3K27M loss is most striking at SB939-upregulated genes suggesting the role in repression of these genes. In addition, genes previously reported as H3K27M-dependent become downregulated in response to SB939 treatment. We discover that the SB939-mediated loss of H3.3K27M is partially blocked by a lysosomal inhibitor, chloroquine. Moreover, the loss of H3.3K27M is facilitated by co-occurrence of H2A.Z, as evidenced by the knock-down of H2A.Z histone isoforms. ChIPseq analysis confirms the occupancy of H3.3K27M and H2A.Z at the same SB939-inducible genes. Altogether, we provide new insight into disease-specific mechanism of HDAC inhibition and demonstrate pharmacological modulation of the oncogenic H3.3K27M protein levels. These findings open a new possibility to directly target the H3.3K27M oncohistone, which may be exploited in future therapies.

cancer biology↗

bioRxiv2022

Hypoxia-mediated regulation of DDX5 through decreased chromatin accessibility and post-translational targeting restricts R-loop accumulation

Local hypoxia occurs in most solid tumors and is associated with aggressive disease and therapy resistance. Widespread changes in gene expression play a critical role in the biological response to hypoxia. However, most research has focused on hypoxia-inducible genes as opposed to those which are decreased in hypoxia. We demonstrate that chromatin accessibility is decreased in hypoxia, predominantly at gene promoters and specific pathways are impacted including DNA repair, splicing and the R-loop interactome. One of the genes with decreased chromatin accessibility in hypoxia was DDX5, encoding the RNA helicase, DDX5, which showed reduced expression in various cancer cell lines in hypoxic conditions, tumor xenografts and in patient samples with hypoxic tumors. Most interestingly, we found that when DDX5 is rescued in hypoxia, replication stress and R-loop levels accumulate further, demonstrating that hypoxia-mediated repression of DDX5 restricts R-loop accumulation. Together these data support the hypothesis that a critical part of the biological response to hypoxia is the repression of multiple R-loop processing factors, however, as shown for DDX5, their role is specific and distinct.

cancer biology↗

bioRxiv2022

Size matters - the impact of nucleus size on results from spatial transcriptomics

Visium Spatial Gene Expression (ST) is a method combining histological spatial information with transcriptomics profiles directly from tissue sections. The use of spatial information has made it possible to discover novel modes of gene expression regulations. However, in the ST experiment, the nucleus size of cells may exceed the thickness of a tissue slice. This may, in turn, negatively affect comprehensive capturing the transcriptomics profile in a single slice, especially for tissues having large differences in the size of nuclei. Here, we defined the effect of Consecutive Slices Data Integration (CSDI) on results from spatial transcriptomic study of human postmortem brains. CSDI can be applied to investigate consecutive sections studied with ST in the human cerebral cortex, avoiding misinterpretation of spot clustering and annotation, increasing accuracy of cell recognition as well as improvement in uncovering the layers of grey matter in the human brain.

bioinformatics↗

bioRxiv2019

Mapping chromatin accessibility and active regulatory elements reveals new pathological mechanisms in human gliomas

Chromatin structure and accessibility, and combinatorial binding of transcription factors to regulatory elements in genomic DNA control transcription. Genetic variations in genes encoding histones, epigenetics-related enzymes or modifiers affect chromatin structure/dynamics and result in alterations in gene expression contributing to cancer development or progression. Gliomas are brain tumors frequently associated with epigenetics-related gene deregulation. We performed whole-genome mapping of chromatin accessibility, histone modifications, DNA methylation patterns and transcriptome analysis simultaneously in multiple tumor samples to unravel novel epigenetic dysfunctions driving gliomagenesis. Based on the results of the integrative analysis of the acquired profiles, we created an atlas of active enhancers and promoters in benign and malignant gliomas. We explored these elements and intersected with Hi-C data to uncover molecular mechanisms instructing gene expression in gliomas. SignificanceEpigenetics-driven deregulation of gene expression accompanies cancer development, but its comprehensive characterization in cancer patients is fragmentary. We performed whole-genome profiling of gene expression, open chromatin, histone modifications and DNA-methylation profiles in the same samples from benign and malignant gliomas. Our study provides a first comprehensive atlas of active regulatory elements in gliomas, which allowed identification of the functional enhancers and promoters in patient samples. This comprehensive approach revealed epigenetic patterns influencing gene expression in benign gliomas and a new pathogenic mechanism involving FOXM1-driven network in glioblastomas. This atlas provides a common set of elements for cross-comparisons of existing and new datasets, prompting novel discoveries and better understanding of gliomagenesis. HighlightsO_LIWe provide an atlas of cis-regulatory elements active in human gliomas C_LIO_LIEnhancer-promoter contacts operating in gliomas are revealed C_LIO_LIDiverse enhancer activation is pronounced in malignant gliomas C_LIO_LIChromatin loop activates FOXM1-ANXA2R pathological network in glioblastomas. C_LI

cancer biology↗

bioRxiv2019

Single-cell RNA sequencing reveals functional heterogeneity and sex differences of glioma-associated brain macrophages

Microglia are resident myeloid cells in the central nervous system (CNS) that control homeostasis and protect CNS from damage and infections. Microglia and peripheral myeloid cells accumulate and adapt tumor supporting roles in human glioblastomas that show prevalence in men. Cell heterogeneity and functional phenotypes of myeloid subpopulations in gliomas remain elusive. Single-cell RNA sequencing (scRNA-seq) of CD11b+ myeloid cells in naive and GL261 glioma-bearing mice revealed distinct profiles of microglia, infiltrating monocytes/macrophages and CNS border-associated macrophages. We demonstrated an unforeseen molecular heterogeneity among myeloid cells in naive and glioma-bearing brains, validated selected marker proteins and showed distinct spatial distribution of identified subsets in experimental gliomas. We found higher expression of MHCII encoding genes in glioma-activated male microglia, which was corroborated in bulk and scRNA-seq data from human diffuse gliomas. Sex-specific gene expression in glioma-activated microglia may be relevant to sex differences in incidence and outcomes of glioma patients.

cancer biology↗