Biology subjects

Garcia-Baucells, J.

Publications and source records attributed to Garcia-Baucells, J..

3 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

Centriolar satellites are sites of translation of centrosomal and ciliary proteins

Centriolar satellites are cytoplasmic particles found in the vicinity of centrosomes and cilia whose functional contribution to the formation of these cellular structures has long been unclear. By characterizing the main scaffolding component of satellites, PCM1 or Combover in Drosophila, we show that satellites are not involved in cellular trafficking as previously thought but rather act as sites for the coordinate translation of centrosomal and ciliary proteins through the interaction with a set of RNA binding proteins and proteins involved in quality control. Strikingly, the concentration of satellites near centrosomes and cilia in vertebrates is not a conserved feature and therefore dispensable for satellite function. Such coordinate synthesis may be a general feature in eukaryotic cells to facilitate protein complex formation and cellular compartmentalization. One-Sentence SummaryCentriolar satellites facilitate the coordinate synthesis of centrosomal and ciliary proteins.

cell biology↗

bioRxiv2021

CYK-1/Formin activation in cortical RhoA signaling centers promotes organismal left-right symmetry breaking

1Proper left-right symmetry breaking is essential for animal development and in many species the actin cytoskeleton plays an instrumental role in this process. Active torque generation in the actomyosin layer promotes left-right symmetry breaking in C. elegans embryos by driving chiral counter-rotating cortical flows. While both Formins and Myosins have been implied in left-right symmetry breaking, and both can rotate actin filaments in vitro, it remains unclear if active torques in the actomyosin cortex are generated by Formins, Myosins, or both. We combined the strength of C. elegans genetics with quantitative imaging and thin film, chiral active fluid theory to show that, while Non-Muscle Myosin II activity drives cortical actomyosin flows, it is permissive for chiral counter-rotation and dispensable for chiral symmetry breaking of cortical flows. Instead, we find that CYK-1/Formin activation in RhoA foci is instructive for chiral counter-rotation and promotes in-plane, active torque generation in the actomyosin cortex. Notably, we observe that artificially generated large active RhoA patches undergo rotations with consistent handedness in a CYK-1/Formin-dependent manner. Altogether, we conclude that, CYK-1/Formin-dependent active torque generation facilitates chiral symmetry breaking of actomyosin flows and drives organismal left-right symmetry breaking in the nematode worm. 2 SignificanceActive torque generation in the actin cytoskeleton has been implicated in driving left-right symmetry breaking of developing embryos, but which molecules generate the active torque and how active torque generation is organized subcellularly remains unclear. This study shows that cortical Formin, recruited to cortical regions where RhoA signaling is active, promotes active torque generation in the actomyosin layer. We find that active torque tends to locally rotate the cortex in a clockwise fashion, which drives the emergence of chiral counter-rotating flows with consistent handedness and facilitates left-right symmetry breaking of C. elegans embryos.

developmental biology↗