Biology subjects

Sobrevals Alcaraz, P.

Publications and source records attributed to Sobrevals Alcaraz, P..

3 recordsLinked to original sources

bioRxiv2025

Unconventional components complement the cryptic kinetochore of the ciliate Tetrahymena thermophila

The accurate segregation of chromosomes is mediated by kinetochores, multi-protein structures that connect centromeric chromatin to the dynamic microtubules of the spindle apparatus. Comparative genomics surveys predict a complex kinetochore in the last eukaryotic common ancestor (LECA) and recurrent loss or replacement of its subcomplexes across the eukaryotic tree of life. Understanding kinetochore composition and organization in diverse lineages can reveal the trajectories of kinetochore evolution in eukaryotes and aid in dissecting the function of each subcomplex. Tetrahymena thermophila is a unicellular eukaryote of the phylum Ciliophora with a largely elusive kinetochore composition. Here, we leverage proximity proteomics coupled to deep homology detection approaches to identify 16 kinetochore proteins in T. thermophila, dubbed KiTTs (Kinetochore of Tetrahymena thermophila 1-16). We find that nine KiTTs (3-9 + 15-16) are cryptic orthologs of conventional kinetochore proteins that previously remained undetected due to extensive sequence divergence. Four KiTTs (10-13) are not orthologous to known subunits and therefore represent unconventional kinetochore proteins. Super-resolution imaging places three of these novel proteins (KiTT10/11/13) at the inner kinetochore, whereas the fourth (KiTT12) localizes near the MIS12 complex at the outer kinetochore. RNAi-mediated depletion of KiTT12 reduces levels of the outer kinetochore protein KiTT1NDC80 and causes chromosome segregation errors, showcasing a bona fide role at the kinetochore. Our work reveals a unique kinetochore composition in a ciliate, providing new insights into the evolution of an essential cellular protein machine.

cell biology↗

bioRxiv2025

Bioengineering Developmentally Inspired Matrix Vesicles as Designer Nanotherapeutics for Bone Regeneration

Extracellular vesicles (EVs) are emerging as promising acellular nanotherapeutics for musculoskeletal repair. Matrix vesicles, a matrix-bound subset of EVs, are essential mediators of endochondral ossification in bone development and fracture repair. This study aims to design bioengineered matrix vesicles from hypertrophic cartilage microtissues to drive endochondral ossification for bone repair. Human mesenchymal stromal cell (hBMSC) microtissues were differentiated with/without BMP2 in chondrogenic or hypertrophic medium. Isolated matrix vesicles were characterized for physiochemical properties and biological functionality. BMP2 and hypertrophic conditioning significantly increased vesicle yield (1.5-fold), alkaline phosphatase activity (3.24-fold), calcium binding capacity (8.82-fold), and growth factor content (BMP2, VEGF). These vesicles promoted proliferation, migration, and mineralization of hBMSCs and enhanced angiogenesis in human endothelial colony forming cells (hECFCs), with BMP2 and hypertrophically conditioned vesicles showing the most pronounced effects. Proteomics analysis confirmed the enrichment of proteins involved in extracellular matrix remodelling, mineral deposition and vascularization within these hypertrophically engineered vesicles. These findings demonstrate that hypertrophic induction of cartilaginous microtissues substantially improves the yield and therapeutic potential of matrix vesicles. Taken together, this research unveils a powerful strategy to bioengineer developmentally inspired vesicles that not only recapitulate key cues of endochondral ossification but offers a tailorable, multifunctional nanotherapeutic platform for improved bone regeneration strategies. Graphical abstract O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=112 SRC="FIGDIR/small/684111v1_ufig1.gif" ALT="Figure 1"> View larger version (37K): org.highwire.dtl.DTLVardef@17327a9org.highwire.dtl.DTLVardef@1310583org.highwire.dtl.DTLVardef@160f095org.highwire.dtl.DTLVardef@152eff0_HPS_FORMAT_FIGEXP M_FIG C_FIG

bioengineering↗

bioRxiv2023

DNA Double-Strand Break Movement in Heterochromatin Depends on the Drosophila Histone Acetyltransferase Gcn5.

Cells employ diverse strategies to repair double-strand breaks (DSBs), a dangerous form of DNA damage that threatens genome integrity. Eukaryotic nuclei consist of different chromatin environments, each displaying distinct molecular and biophysical properties that can significantly influence the DSB repair process. Specifically, DSBs arising in the compact and silenced heterochromatin domains have been found to move to the heterochromatin periphery in mouse and Drosophila to prevent aberrant recombination events. However, it is poorly understood how chromatin components, such as histone post-translational modifications, contribute to these DSB movements within heterochromatin. Using locus-specific DSB induction in Drosophila tissues and cultured cells, we identify that histone H3 lysine 9 acetylation (H3K9ac) is enriched at DSBs in heterochromatin but not euchromatin. We find that this enrichment is mediated by the histone acetyltransferase dGcn5, which rapidly localizes to heterochromatic DSBs. Moreover, we demonstrate that in the absence of dGcn5, heterochromatic DSBs display impaired recruitment of the SUMO E3 ligase Nse2/Qjt and fail to relocate to the heterochromatin periphery to complete repair. In summary, our results reveal a previously unidentified role for dGcn5 and H3K9ac in heterochromatin DSB repair and underscore the importance of differential chromatin responses at heterochromatic and euchromatic DSBs to promote safe repair.

cell biology↗