Biology subjects

Zampetaki, A.

Publications and source records attributed to Zampetaki, A..

5 recordsLinked to original sources

bioRxiv2025

Centrosome Softening As A Mechanical Adaptation For Mitosis

Centrosomes are microtubule-organizing centers important for mitotic spindle assembly and chromosome segregation. During mitosis, centrosomes are exposed to mechanical forces via the microtubules they nucleate, yet the material properties underlying their response to these forces remain poorly understood. In this study, we systematically probed the mechanical behavior of C. elegans centrosomes, both in vitro and in vivo. Using microtubule perturbations and quantitative live cell imaging, we found that centrosomes become increasingly deformed during mitosis. Centrosome deformation is independent of cortical pulling forces but instead results from microtubule polymerization within the pericentriolar material. This deformation impacts centrosome size: as microtubule number decreases with cell volume in early cleavage divisions, centrosome size scales proportionately. To directly measure centrosome elasticity, we employed atomic force microscopy (AFM) on isolated centrosomes in vitro and Brillouin light scattering microscopy in developing embryos in vivo. Both approaches revealed that centrosomes progressively soften during mitosis. Theoretical modeling predicts that softening serves to dampen spindle force fluctuations, helping to protect kinetochore-microtubule interactions and safeguarding chromosome segregation. Further, softening may enhance centrosomal microtubule nucleation capacity, facilitating mitotic spindle assembly, particularly in large early embryonic cells. We propose that centrosome softening is a mechanical adaptation for mitosis that couples microtubule number to centrosome size through force-dependent deformation. This optimally balances two mitotic requirements: the need for robust microtubule nucleation and the ability to withstand spindle forces, thereby ensuring accurate cell division.

cell biology↗

bioRxiv2024

Cellular context specific tuning of actomyosin ring contractility within a common cytoplasm

Actomyosin rings are specializations of the non-muscle actomyosin cytoskeleton that drive cell shape changes during division, wound healing, and other events. Contractile rings throughout phylogeny and in a range of cellular contexts are built from conserved components including non-muscle myosin II, actin filaments, and crosslinking proteins. To explore whether diverse actomyosin rings generate contractile force and close via a common mechanism, we studied three instances of ring closure within the continuous cytoplasm of the C. elegans syncytial oogenic germline: mitotic cytokinesis of germline stem cells, apoptosis of meiotic compartments, and cellularization of oocytes. The three ring types exhibited distinct closure kinetics and component protein abundance dyanmics. We formulated a physical model to relate measured closure speed and molecular composition dynamics to ring active stress and viscosity. We conclude that these ring intrinsic factors vary among the ring types. Our model suggests that motor and non-motor crosslinkers abundance and distribution along filaments are important to recapitulate observed closure dynamics. Thus, our findings suggest that across ring closure contexts, fundamental contractile mechanics are conserved, and the magnitude of contractile force is tuned via regulation of ring component abundance and distribution. These results motivate testable hypotheses about cytoskeletal regulation, architecture, and remodeling.

cell biology↗

bioRxiv2023

The translation of a short open reading frame product within the human TUBA1B gene regulates cancer cell proliferation by importin-β

Understanding cancer biology is crucial for improving treatment strategies. This study identified TUBA1B-sORF1, a short open reading frame product alternatively translated from the human -tubulin gene (TUBA1B), which has a completely different amino acid sequence from the -tubulin 1B chain. TUBA1B-sORF1 is highly expressed in cancer cell lines and gastric carcinoma. Both methionine-initiated canonical and leucine-initiated noncanonical translations of TUBA1B-sORF1 coexist in cancer cells, and there is a transition between sORF1 and -tubulin translations, evidenced by the TUBA1B-sORF1/-tubulinlow/- subpopulation. Knocking down TUBA1B-sORF1 reduces cancer cell proliferation and tumorigenicity. TUBA1B-sORF1 facilitates protein nuclear translocation, leading to the upregulation of proliferation-promoting genes and downregulation of proliferation-inhibiting genes. Specifically, it forms a complex with importin {beta} and {beta}-catenin, promoting {beta}-catenin nuclear translocation and target gene transcription. These findings reveal that TUBA1B is a polycistronic gene translating at least two entirely different proteins: -tubulin and TUBA1B-sORF1. The variable translation between them may regulate tumorigenesis, making TUBA1B-sORF1 a promising therapeutic target and diagnostic biomarker for cancer treatment.

cancer biology↗

bioRxiv2022

Human blood vessel organoids reveal a critical role for CTGF in maintaining microvascular integrity

The microvasculature plays a key role in tissue perfusion, transport of mediators, and exchange of gases and metabolites to and from tissues. Microvascular dysfunction has emerged as an important contributor to cardiovascular diseases. In this study we used human blood vessel organoids (BVOs) as a model of the microvasculature to delineate the mechanisms of microvascular dysfunction caused by metabolic rewiring. BVOs fully recapitulated key features of the normal human microvasculature, including reliance of mature endothelial cells (ECs) on glycolytic metabolism, as concluded from metabolic flux assays using 13C-glucose labelling and mass spectrometry-based metabolomics. Treatment of BVOs with PFK15, a pharmacological inhibitor of glycolysis, resulted in rapid tissue restructuring, vessel regression with reduced pericyte coverage and alterations in tight junction morphology. Proteomic analysis of the BVO secretome revealed remodelling of the extracellular matrix and differential expression of paracrine mediators such as CTGF. Treatment with recombinant CTGF recovered tight junction formation and increased pericyte coverage in microvessels. Our metabolic and proteomics findings demonstrate that BVOs rapidly undergo restructuring in response to metabolic changes and identify CTGF as a critical paracrine regulator of microvascular integrity.

cell biology↗

bioRxiv2022

Impaired Function in Diabetic Patient iPSCs-derived Blood Vessel Organoids Stem from a Subpopulation of Vascular Cells

The presence of both endothelial cells (ECs) and mural cells are central to the proper function of blood vessels in health and pathological changes in diseases including diabetes. Although iPSCs-derived vascular organoids (VOs) provide an appealing in vitro disease model and platform for drug screening, whether these organoids recapitulate human disease remains debatable. Here, we show human diabetic (DB)-VOs represent impaired vascular function including enhanced ROS activity, with higher mitochondrial content and activity, increased pro-inflammatory cytokines, and less regenerative potential in vivo. Using single-cell RNA sequencing, we identify all specialized types of vascular cells (artery, capillary, vein, lymphatic and tip cells, as well as pericytes and vSMCs) within vascular organoids, while demonstrating the dichotomy landscape of ECs and mural cells. Furthermore, we reveal basal heterogeneity within vascular organoids and demonstrate differences between diabetic and non-diabetic VOs. Of note, a subpopulation of ECs significantly enrich for ROS and oxidative phosphorylation hallmarks in DB-VOs, may represent early signs of aberrant angiogenesis in diabetes. This study helps to identify key biomarkers for diabetic disease progression and find signalling molecules amenable to drug intervention.

cell biology↗