Biology subjects

Bayraktar, S.

Publications and source records attributed to Bayraktar, S..

7 recordsLinked to original sources

bioRxiv2025

Ceudovitox: a novel pseudotyped-virus screening platform to identify cell entry factors for high consequence infections.

Development of scalable and highly adaptable platforms to characterise high consequence infections are essential for limiting the impact of future viruses with pandemic potential. As part of this, an understanding of the virus-host interactions is vital, with the cell entry mechanism being crucial for the development of therapeutics and vaccines. Current approaches in this field depend on assays with authentic (live) viruses that require high containment facilities. However, these are hindered by high costs, need for highly trained staff, slow processing times and limited scalability. Using pseudotyped viruses (PV) expressing the chikungunya (CHIKV) envelope protein as a proof-of-principle, we developed a novel screening platform, Ceudovitox, to identify cellular factors involved in viral entry. PVs were engineered to express the herpes simplex virus-1 thymidine kinase, which following addition of ganciclovir, can selectively kill infected cells. Then a heterogenous pool of knockout cells were produced using the CRISPR-Cas9 library. Infection of these cells with the "killer" PV system permitted positive selection of cells refractory to viral infection and, through next generation sequencing, identification of a number of factors involved in CHIKV entry. Matrix metalloproteinases were identified as novel entry factors and demonstrated that MMP-targeting drugs efficiently inhibit PV and authentic CHIKV infections. These results suggest this platform holds great promise as a pandemic-preparedness tool that increases the capacity and speed of screening for cell entry factors. It is also a safe platform able to dissect the gene network involved in virus entry. Ceudovitox will help identify new therapeutic targets, thereby aiding the development of treatments against future outbreaks or pandemic pathogens and making a significant contribution to the "100 days" mission. Author SummaryThe increased threat of the emergence of new viral pathogens with pandemic potential highlights the importance of developing scalable high-throughput screening platforms to quickly characterise new emergent viral pathogens. Improving understanding of virus-host interactions, including how viruses enter cells, can help fast development of new targeted therapeutics and reduce pandemic burdens. Current approaches rely on using live viruses, which are highly infectious and must be manipulated in high containment facilities, which are slow and cumbersome. Our new screening platform, Ceudovitox, is a safer, faster and more scalable alternative. Through using pseudotyped viruses, which can only undergo one replication cycle, we are able to distinguish virus entry factors of high containment viruses within highly abundant low containment facilities, allowing us to quickly characterise potential entry factors of high containment viruses. Within this study, Ceudovitox was shown to recognise both known and novel entry factors of Chikungunya virus; a virus which causes chronic arthralgia and arthritis. Matrix metalloproteinases were amongst novel entry factors identified and were seen to reduce virus infection in both pseudotyped and authentic virus assays, demonstrating how Ceudovitox can correctly discover virus entry factors of live high containment viruses. Ceudovitoxs utility as a screening platform for high containment viruses and new emerging pathogens, has the potential increase understanding and speed up the development of new therapeutics during pandemics, helping to reach the 100 Day Mission of pandemic preparedness.

molecular biology↗

bioRxiv2025

Spatial transcriptomics uncovers hybrid, pro-inflammatory and pro-fibrotic cellular niches in pulmonary granuloma of patients with chronic sarcoidosis

BackgroundSarcoidosis is a disease of unknown etiology characterized by the formation of immune cell accumulation (granuloma) in the lung and other tissues. Chronic sarcoidosis may lead to pulmonary fibrosis. AimTo unravel cellular niches within pulmonary granuloma of chronic sarcoidosis patients using spatial transcriptomics. MethodsSpatial transcriptomics using the Visium platform (10x Genomics) was performed on nine granuloma-containing lung explants from sarcoidosis patients. Validation of gene expression was performed through immunohistofluorescence protein staining and RNA in situ hybridization. ResultsSpatial gene expression covered 30,587 gene expression spots and 173 granulomas. A CD68+ macrophage niche was localized in the center of the granuloma, with a CD3+ T and CD20+ B cell niche in close proximity, surrounded by a COL3A1+ fibroblast niche. In the central granuloma macrophage niche, expression of the pro-fibrotic macrophage genes SPP1, CHIT1 and CHI3L1 was observed, genes whose expression has recently been described for macrophages in idiopathic pulmonary fibrosis. Additionally, pro-inflammatory macrophage genes were expressed in the central granuloma niche: macrophages appear armed for lysosomal degradation and ready for phagocytosis. Inner granuloma niches showed high responsiveness to interferon gamma (IFN-{gamma}), expressing a multitude of IFN-{gamma}-induced genes. High collagen and CTHRC1 expression were observed in granuloma fibroblasts niches, characteristics of pro-fibrotic lung remodeling. Ligand-receptor analysis identified pro-inflammatory and pro-fibrotic interactions between granuloma niches. ConclusionTaken together, macrophages in the center of the sarcoidosis granuloma form an armed-and-ready, hybrid pro-inflammatory and pro-fibrotic niche, supporting granuloma persistence through continuous IFN-{gamma}-stimulation and fibrotic remodeling conducted by fibrotic fibroblasts surrounding the granuloma.

molecular biology↗

bioRxiv2024

Multiomic analysis reveals developmental dynamics of the human heart in health and disease

Developmental dynamics involve the specification of diverse cell types and their spatial organization into multicellular niches. Here, we combine single-cell and spatial multiomics to define 19 distinct tissue niches in the developing heart, leading to the development of a context-aware, resolution-agnostic niche classification tool (TissueTypist). Applying high-resolution spatial profiling to the developing sinoatrial node, we resolve three pacemaker cell subtypes arrayed along a linear axis. First trimester subpopulations, such as the pacemaker cells in the sinus horn and sinoatrial node head region, display neuro-attractant programmes and interact with parasympathetic neurons via interactions including Semaphorin-Plexin signalling. Temporal trajectories map maturation of atrial and ventricular cardiomyocytes, uncovering a lipid-metabolic switch and potential key regulators of cell type identity. In the ventricle, we identify cellular and transcriptional gradients along both pseudotime and transmural axes, offering new molecular insights into myocardial compaction and maturation. Comparative profiling of euploid and trisomy 21 hearts shows a depletion of compact cardiomyocytes and heightened apoptosis, validated in isogenic-matched trisomy 21 and euploid iPSC-derived cardiomyocytes. This implicates disrupted myocardial growth may be a mechanism for Downs syndrome-associated congenital heart disease. Overall, we deliver a spatially resolved framework of human cardiac development, enabling systematic exploration of developmental niches in health and disease.

developmental biology↗

bioRxiv2024

High-resolution atlas of the developing human heart and the great vessels

The human heart and adjoining great vessels consist of multiple cell types essential for life, yet many remain uncharacterised molecularly during development. Here, we performed a high-resolution profiling of the developing heart and great vessels between 4 and 20 post-conception weeks using single-cell and spatial transcriptomics defining 63 cell types with distinct identity and location-specific signatures. We reveal previously unreported molecular identities in cell types, including the pericardium and the ductus arteriosus. In the cardiomyocytes, we identify signatures of the trabeculated-compact, and right-left axes of ventricular cardiomyocytes. In vessels, we distinguish the constituents belonging to either coronary or great vessels. We confirm our transcriptional findings spatially, revealing nuanced signatures with specific zonation patterns and validating this atlas as a curated transcriptional reference for future studies. We leverage the temporal scope of the presented atlas to build CMageR, a predictive pipeline for scRNA-seq combining cardiac cell annotation with a transcriptional cardiac clock of single-cell developmental age for each cell type. Our cardiomyocyte clock captures dynamic biology, revealing core functional changes and novel markers of maturity during the first and second trimester. Finally, we benchmark in vitro models, suggesting a transcriptional right-chamber bias in stem cell derived cardiomyocytes with the oldest model age-matched to 12 post-conception weeks. Collectively, our work provides a high-resolution atlas of human cardiac development to enhance our understanding of function in development, health, and disease, and a foundation for building a rich reference to benchmark and improve in vitro models.

developmental biology↗

bioRxiv2023

CRISPR screens in 3D tumourspheres identified miR-4787-3p as a transcriptional start site miRNA essential for breast tumour-initiating cell growth

Breast cancer (BC) is a heterogeneous malignancy with distinct molecular subtypes and clinical characteristics. Tumour-initiating cells (TICs) are a small subset of cancer cells that are responsible for tumour initiation and progression. Our study employed pooled CRISPR screens, integrating 2D and 3D culture models, to identify miRNAs critical in BC tumorsphere formation. These screens combined with RNA-seq experiments allowed us to identify the miRNA signature and their targets that are essential for tumoursphere growth. Amongst them, miR-4787-3p exhibited significant up-regulation in BC, particularly in basal-like BCs, suggesting its association with aggressive disease phenotypes. Surprisingly, despite its location within the 5UTR of a protein coding gene, which define DROSHA-independent transcription start site (TSS)-miRNAs, our findings revealed its dependence on both DROSHA and DICER1 for maturation. Inhibition of miR-4787-3p hindered tumorsphere formation, highlighting its potential as a therapeutic target in BC. Moreover, our study proposes elevated miR-4787-3p expression as a potential prognostic biomarker for adverse outcomes in BC patients. We found that protein-coding genes positively selected in the CRISPR screens were enriched of miR-4787-3p putative targets. Amongst these identified key targets, we selected ARHGAP17, FOXO3A, and PDCD4 because are known tumour suppressors in cancer and experimentally validated the interaction of miR-4787-3p with their 3UTRs. Our work illuminates the molecular mechanisms underpinning miR-4787-3ps oncogenic role in BC. These findings advocate for further clinical investigations targeting miR-4787-3p and underscore its prognostic significance, offering promising avenues for tailored therapeutic interventions and prognostic assessments in BC.

cell biology↗

bioRxiv2021

Unravelling Form and Function: Improved function of engineered cardiac tissue through extra-cellular anisotropy

Cardiac tissue engineering is a promising therapeutic option for myocardial repair after injury, however, so far engineered heart patches have shown limited translational utility due to poor electrical integration and tissue contractility. Emerging research suggests that scaffolds that recapitulate the three-dimensional structure of the native myocardium improve physiological function. Complex scaffold fabrication remains a technical challenge and the isolated impact of scaffold architecture on tissue function and cellular physiology is poorly understood. Here, we provided a direct comparison between isotropic and aligned collagen scaffold morphologies where all confounding physio-mechanical features, such as strut wall thickness and surface roughness are conserved. This enabled the independent and systematic assessment of the effects of pore macro-architecture on global tissue function and cellular maturation. We seeded our scaffolds with embryonic stem cell derived cardiomyocytes (hESC-CM) and measured tissue function through calcium signal transduction and dynamic contractile strain. The aligned tissue constructs facilitated improved signalling synchronicity and directional contractility. We further examined the influence of scaffold macrostructure on intercellular organization and intracellular development. Cells on aligned constructs conformed to the orientation of the scaffold macro-structure and were found to have phenotypic and genetic markers of increased maturity. Our results isolate the influence of scaffold macro-structure on engineered tissue function at multiple length scales. These findings inform the design of optimized cardiac tissue and expand the potential for engineered tissue in regenerative and model medical systems by reducing the gaps in tissue functionality that limit their utility.

bioengineering↗

bioRxiv2019

A deregulated stress response underlies distinct INF2 associated disease profiles

Monogenic diseases provide favorable opportunities to elucidate the molecular mechanisms of disease progression and improve medical diagnostics. However, the complex interplay between genetic and environmental factors in disease etiologies makes it difficult to discern the mechanistic links between different alleles of a single locus and their associated pathophysiologies. Here we systematically characterize a large panel (>50) of autosomal dominant mutants of the actin regulator inverted formin 2 (INF2) that have been reported to cause the podocytic kidney disease focal segmental glomerulosclerosis (FSGS) and the neurological disorder Charcot Marie-Tooth disease (CMT). We found that INF2 mutations lead to deregulated activation of the formin and a constitutive stress response in cultured cells, primary patient cells and Drosophila nephrocytes. Using quantitative live-cell imaging we were able to identify distinct subsets of INF2 variants that exhibit varying degrees of activation. Furthermore, we could clearly distinguish between INF2 mutations that were linked exclusively to FSGS from those that caused a combination of FSGS and CMT. Our results indicate that cellular profiling of disease-associated mutations can contribute substantially to sequence-based phenotype predictions.

cell biology↗