title: Robust gap repair in the contractile ring ensures timely completion of cytokinesis.
abstract: Cytokinesis in animal cells requires the constriction of an actomyosin contractile ring, whose architecture and mechanism remain poorly understood. We use laser microsurgery to explore the biophysical properties of constricting rings in Caenorhabditis elegans embryos. Laser cutting causes rings to snap open. However, instead of disintegrating, ring topology recovers and constriction proceeds. In response to severing, a finite gap forms and is repaired by recruitment of new material in an actin polymerization-dependent manner. An open ring is able to constrict, and rings repair from successive cuts. After gap repair, an increase in constriction velocity allows cytokinesis to complete at the same time as controls. Our analysis demonstrates that tension in the ring increases while net cortical tension at the site of ingression decreases throughout constriction and suggests that cytokinesis is accomplished by contractile modules that assemble and contract autonomously, enabling local repair of the actomyosin network. Consequently, cytokinesis is a highly robust process impervious to discontinuities in contractile ring structure.
authors.affiliation: Instituto de Investigação e Inovação em Saúde, Universidade do Porto, 4200-135 Porto, Portugal.|Instituto de Biologia Molecular e Celular, 4200-135 Porto, Portugal.
authors.forename: Ana M
authors.identifier: http://orcid.org/0000-0002-1840-1473
authors.initials: AM
authors.lastname: Silva
authors.affiliation: Instituto de Investigação e Inovação em Saúde, Universidade do Porto, 4200-135 Porto, Portugal.|Instituto de Biologia Molecular e Celular, 4200-135 Porto, Portugal.
authors.forename: Daniel S
authors.identifier: http://orcid.org/0000-0003-4144-8189
authors.initials: DS
authors.lastname: Osório
authors.affiliation: Instituto de Investigação e Inovação em Saúde, Universidade do Porto, 4200-135 Porto, Portugal.|Instituto de Biologia Molecular e Celular, 4200-135 Porto, Portugal.
authors.forename: Antonio J
authors.identifier: http://orcid.org/0000-0002-1053-8715
authors.initials: AJ
authors.lastname: Pereira
authors.affiliation: Instituto de Investigação e Inovação em Saúde, Universidade do Porto, 4200-135 Porto, Portugal.|Instituto de Biologia Molecular e Celular, 4200-135 Porto, Portugal.
authors.forename: Helder
authors.initials: H
authors.lastname: Maiato
authors.affiliation: International Iberian Nanotechnology Laboratory, 4715-330 Braga, Portugal.
authors.forename: Inês Mendes
authors.initials: IM
authors.lastname: Pinto
authors.affiliation: Stowers Institute for Medical Research, Kansas City, MO 64110.
authors.forename: Boris
authors.initials: B
authors.lastname: Rubinstein
authors.affiliation: Instituto de Investigação e Inovação em Saúde, Universidade do Porto, 4200-135 Porto, Portugal.|Instituto de Biologia Molecular e Celular, 4200-135 Porto, Portugal.
authors.forename: Reto
authors.identifier: http://orcid.org/0000-0002-0360-2977
authors.initials: R
authors.lastname: Gassmann
authors.affiliation: Instituto Gulbenkian de Ciência, Fundação Calouste Gulbenkian, 2780-156 Oeiras, Portugal.
authors.forename: Ivo Andreas
authors.identifier: http://orcid.org/0000-0003-4444-1046
authors.initials: IA
authors.lastname: Telley
authors.affiliation: Instituto de Investigação e Inovação em Saúde, Universidade do Porto, 4200-135 Porto, Portugal anacarvalho@ibmc.up.pt.|Instituto de Biologia Molecular e Celular, 4200-135 Porto, Portugal.
authors.forename: Ana Xavier
authors.identifier: http://orcid.org/0000-0002-2256-7134
authors.initials: AX
authors.lastname: Carvalho
mesh_terms: D000205:Actomyosin / Q000378:metabolism*; D000818:Animals; D019086:Bridged Bicyclo Compounds, Heterocyclic / Q000494:pharmacology; D017173:Caenorhabditis elegans / Q000166:cytology* / Q000187:drug effects / Q000196:embryology; D048749:Cytokinesis; D004625:Embryo, Nonmammalian / Q000166:cytology; D007834:Lasers; D008866:Microsurgery; D053778:Thiazolidines / Q000494:pharmacology
chemical_list: D019086:Bridged Bicyclo Compounds, Heterocyclic; D053778:Thiazolidines; D000205:Actomyosin; C037067:latrunculin A