Biology subjects

Karagianni, E.

Publications and source records attributed to Karagianni, E..

3 recordsLinked to original sources

bioRxiv2026

High-throughput platforms for genetic perturbation screening using CRISPR/Cas9 in human iPSC-derived macrophages for drug discovery

Human induced Pluripotent Stem Cell (hiPSC) models have revolutionised drug discovery, offering high translational relevance for recapitulating disease biology and thereby the potential to help reduce drug attrition. Macrophages are pivotal for maintaining tissue homeostasis and orchestrating immune responses; their dysregulation underpins several diseases, including autoinflammatory disorders, neurodegeneration, and cancer. Therapeutically targeting this cell type presents an attractive strategy to simultaneously influence multiple cellular mediators and functions. We have established a scalable, semi-automated, and physiologically relevant hiPSC-derived macrophage model, rigorously characterised through deep comparative multi-omics. We have also integrated our hiPSC-derived macrophage platform with large-scale CRISPR screening workflows designed for parallel genetic interrogation of thousands of gene targets, in both arrayed and pooled formats. In this manuscript, we apply those genetic screening methods to hiPSC-derived macrophages and showcase how genetic perturbations alter pro- and anti-inflammatory transcriptional signatures and significantly impact functional phenotypes in this cell model. This integrated approach allows for the exploration of novel genetic insights linked to causal disease biology, advancing myeloid cell-associated target discovery across a broad spectrum of therapeutic areas.

immunology↗

bioRxiv2025

Brachyury expression levels predict lineage potential and axis-forming ability of in vitro derived neuromesodermal progenitors

Neuromesodermal progenitors (NMPs) produce the spinal cord and musculoskeleton in the elongating anterior-posterior axis. In vivo, NMPs possess dual potency, coinciding with regions coexpressing SOX2 and Brachyury (TBXT). In vitro, SOX2/TBXT co-expressing cells can be produced from pluripotent cells and, like their in vivo counterparts, can produce neural tube and somitic mesoderm. However, the functional characteristics of in vitro SOX2/TBXT co-expressing cells remain unclear, confounding comparisons with in vivo data. To address this, we developed a dual Sox2/Tbxt reporter mouse ESC line. SOX2/TBXT reporter-positive cells emerge in vitro from pluripotent populations with dynamics that mirror their appearance in the embryo. Purified SOX2/TBXT co-expressing populations can differentiate towards neurectoderm or mesoderm, including lateral mesoderm upon BMP stimulation. In gastruloids, quantitative live imaging shows that WNT or NOTCH inhibition rapidly leads to downregulation of TBXT expression and diminished axial extension. We show that clonally plated SOX2/TBXT co-expressing cells are bipotent NMPs that can also self-propagate. By combining clonal analysis with mathematical modelling, we identify two thresholds of SOX2/TBXT expression, switching clonal output from neural- to mesoderm-biased, and from mesoderm-biased to mesoderm-specified. Media and substrate composition alter the lineage outcomes of in vitro derived mouse NMPs. Thus, this Sox2/Tbxt double reporter cell line provides support for unsuspected heterogeneity in NMPs, together with evidence for a role of these transcription factors in directing cell fate to drive axis elongation.

developmental biology↗

bioRxiv2024

Epigenetic histone modifications H3K36me3 and H4K5/8/12/16ac induce open polynucleosome conformations via different mechanisms

Nucleosomes are the basic compaction unit of chromatin and nucleosome structure, and their higher-order assemblies regulate genome accessibility. Many post-translational modifications alter nucleosome dynamics, nucleosome-nucleosome interactions, and ultimately chromatin structure and gene expression. Here, we investigate the role of two post-translational modifications associated with actively transcribed regions, H3K36me3 and H4K5/8/12/16ac, in the contexts of tri-nucleosome arrays that provide a tractable model system for quantitative single-molecule analysis, while enabling us to probe nucleosome-nucleosome interactions. Direct visualization by AFM imaging reveals that H3K36me3 and H4K5/8/12/16ac nucleosomes adopt much more open and loose conformations than unmodified nucleosomes. Similarly, magnetic tweezers force spectroscopy shows a reduction in DNA outer turn wrapping and nucleosome-nucleosome interactions for the modified nucleosomes. The results suggest that for H3K36me3 the increased breathing and outer DNA turn unwrapping seen in mononucleosomes propagates to more open conformations in nucleosome arrays. In contrast, the even more open structures of H4K5/8/12/16ac nucleosome arrays do not appear to derive from the dynamics of the constituent mononucleosomes, but are driven by reduced nucleosome-nucleosome interactions, suggesting that stacking interaction can overrule DNA breathing of individual nucleosomes. We anticipate that our methodology will be broadly applicable to reveal the influence of other post-translational modifications and action of nucleosome remodelers.

biophysics↗