@article{silva_chan_norman_sobral_zanin_gassmann_belmonte_carvalho_2023, title={β-heavy-spectrin stabilizes the constricting contractile ring during cytokinesis}, volume={222}, ISSN={["1540-8140"]}, url={https://doi.org/10.1083/jcb.202202024}, DOI={10.1083/jcb.202202024}, abstractNote={Cytokinesis requires the constriction of an actomyosin-based contractile ring and involves multiple F-actin crosslinkers. We show that partial depletion of the C. elegans cytokinetic formin generates contractile rings with low F-actin levels that constrict but are structurally fragile, and we use this background to investigate the roles of the crosslinkers plastin/PLST-1 and β-heavy-spectrin/SMA-1 during ring constriction. We show that the removal of PLST-1 or SMA-1 has opposite effects on the structural integrity of fragile rings. PLST-1 loss reduces cortical tension that resists ring constriction and makes fragile rings less prone to ruptures and regressions, whereas SMA-1 loss exacerbates structural defects, leading to frequent ruptures and cytokinesis failure. Fragile rings without SMA-1 or containing a shorter SMA-1, repeatedly rupture at the same site, and SMA-1::GFP accumulates at repair sites in fragile rings and in rings cut by laser microsurgery. These results establish that β-heavy-spectrin stabilizes the constricting ring and reveals the importance of β-heavy-spectrin size for network connectivity at low F-actin density.}, number={1}, journal={JOURNAL OF CELL BIOLOGY}, author={Silva, Ana Marta and Chan, Fung-Yi and Norman, Michael J. and Sobral, Ana Filipa and Zanin, Esther and Gassmann, Reto and Belmonte, Julio Monti and Carvalho, Ana Xavier}, year={2023}, month={Jan} }
 @article{adhyapok_piatkowska_norman_clendenon_stern_glazier_belmonte_2021, title={A mechanical model of early somite segmentation}, volume={24}, ISSN={["2589-0042"]}, url={https://doi.org/10.1016/j.isci.2021.102317}, DOI={10.1016/j.isci.2021.102317}, abstractNote={Somitogenesis is often described using the clock-and-wavefront (CW) model, which does not explain how molecular signaling rearranges the pre-somitic mesoderm (PSM) cells into somites. Our scanning electron microscopy analysis of chicken embryos reveals a caudally-progressing epithelialization front in the dorsal PSM that precedes somite formation. Signs of apical constriction and tissue segmentation appear in this layer 3-4 somite lengths caudal to the last-formed somite. We propose a mechanical instability model in which a steady increase of apical contractility leads to periodic failure of adhesion junctions within the dorsal PSM and positions the future inter-somite boundaries. This model produces spatially periodic segments whose size depends on the speed of the activation front of contraction (F), and the buildup rate of contractility (Λ). The Λ/F ratio determines whether this mechanism produces spatially and temporally regular or irregular segments, and whether segment size increases with the front speed.}, number={4}, journal={ISCIENCE}, publisher={Elsevier BV}, author={Adhyapok, Priyom and Piatkowska, Agnieszka M. and Norman, Michael J. and Clendenon, Sherry G. and Stern, Claudio D. and Glazier, James A. and Belmonte, Julio M.}, year={2021}, month={Apr} }
 @article{sobral_chan_norman_osorio_dias_ferreira_barbosa_cheerambathur_gassmann_belmonte_et al._2021, title={Plastin and spectrin cooperate to stabilize the actomyosin cortex during cytokinesis}, volume={31}, ISSN={["1879-0445"]}, url={https://doi.org/10.1016/j.cub.2021.09.055}, DOI={10.1016/j.cub.2021.09.055}, abstractNote={Cytokinesis, the process that partitions the mother cell into two daughter cells, requires the assembly and constriction of an equatorial actomyosin network. Different types of non-motor F-actin crosslinkers localize to the network, but their functional contribution remains poorly understood. Here, we describe a synergy between the small rigid crosslinker plastin and the large flexible crosslinker spectrin in the C. elegans one-cell embryo. In contrast to single inhibitions, co-inhibition of plastin and the βH-spectrin (SMA-1) results in cytokinesis failure due to progressive disorganization and eventual collapse of the equatorial actomyosin network. Cortical localization dynamics of non-muscle myosin II in co-inhibited embryos mimic those observed after drug-induced F-actin depolymerization, suggesting that the combined action of plastin and spectrin stabilizes F-actin in the contractile ring. An in silico model predicts that spectrin is more efficient than plastin at stabilizing the ring and that ring formation is relatively insensitive to βH-spectrin length, which is confirmed in vivo with a sma-1 mutant that lacks 11 of its 29 spectrin repeats. Our findings provide the first evidence that spectrin contributes to cytokinesis and highlight the importance of crosslinker interplay for actomyosin network integrity.}, number={24}, journal={CURRENT BIOLOGY}, publisher={Elsevier BV}, author={Sobral, Ana Filipa and Chan, Fung-Yi and Norman, Michael J. and Osorio, Daniel S. and Dias, Ana Beatriz and Ferreira, Vanessa and Barbosa, Daniel J. and Cheerambathur, Dhanya and Gassmann, Reto and Belmonte, Julio Monti and et al.}, year={2021}, month={Dec}, pages={5415-+} }