{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"institution":[{"name":"bioRxiv"}],"indexed":{"date-parts":[[2026,10,29]],"date-time":"2026-10-29T14:33:44Z","timestamp":1793284424946,"version":"4.5.0"},"posted":{"date-parts":[[2026,8,12]]},"group-title":"Cell Biology","reference-count":59,"publisher":"openRxiv","license":[{"start":{"date-parts":[[2026,8,12]],"date-time":"2026-08-12T00:00:00Z","timestamp":1786492800000},"content-version":"vor","delay-in-days":0,"URL":"http:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"funder":[{"DOI":"10.13039\/100000057","name":"National Institute of General Medical Sciences","doi-asserted-by":"crossref","award":["R35 GM131753"],"award-info":[{"award-number":["R35 GM131753"]}],"id":[{"id":"10.13039\/100000057","id-type":"DOI","asserted-by":"crossref"}]},{"name":"JST FOREST","award":["JPMJFR224O"],"award-info":[{"award-number":["JPMJFR224O"]}]}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":[],"accepted":{"date-parts":[[2026,8,12]]},"abstract":"<jats:title>Abstract<\/jats:title>\n                <jats:p>\n                  Early animal embryos undergo rapid cleavages that partition cytoplasmic volumes orders of magnitude larger than those of somatic cells\n                  <jats:sup>1<\/jats:sup>\n                  . Each division must reposition nuclei and centrosomes and distribute organelles within minutes, over distances up to hundreds of micrometers\n                  <jats:sup>2<\/jats:sup>\n                  . Cleavage furrows are positioned by microtubule asters\n                  <jats:sup>3,4<\/jats:sup>\n                  , but the mechanical mechanism for long-range transport of cytoplasmic components before cytokinesis was unknown. Here, we show that cytoplasm behaves as a locally switchable active material. Fluidization at the midplane allows bulk actomyosin to convert a local mechanical asymmetry into directed global flows of all components as a composite material. Using an actin-intact cycling\n                  <jats:italic>Xenopus<\/jats:italic>\n                  egg extract together with\n                  <jats:italic>Xenopus<\/jats:italic>\n                  and medaka embryos, we find that F-actin mechanically couples microtubule asters, organelles, nuclei and centrosomes into a gel-like composite that propagates forces over hundreds of micrometers. After mitosis, Aurora B kinase patterns a locally fluidized midplane, from which myosin-II contractility drives coherent cytoplasmic flows. A fluid dynamics model accounts for the observed flow geometry and rates. Our results reveal how local control of the material state of cytoplasm converts mitotic symmetry breaking into long-range intracellular transport and identify bulk actomyosin as the active stress generator that partitions embryonic cytoplasm as a composite gel.\n                <\/jats:p>","DOI":"10.64898\/2026.08.11.744254","type":"posted-content","created":{"date-parts":[[2026,8,12]],"date-time":"2026-08-12T12:05:16Z","timestamp":1786536316000},"source":"Crossref","is-referenced-by-count":2,"title":["Local fluidization of an active cytoplasmic gel partitions large cells"],"prefix":"10.64898","author":[{"ORCID":"https:\/\/orcid.org\/0009-0006-8395-0379","authenticated-orcid":false,"given":"Luolan","family":"Bai","sequence":"first","affiliation":[{"name":"Department of Systems Biology, Harvard Medical School, Boston, MA, USA"},{"name":"Department of Molecular and Cellular Biology, Harvard University, Cambridge, MA, USA"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Christine M.","family":"Field","sequence":"additional","affiliation":[{"name":"Department of Systems Biology, Harvard Medical School, Boston, MA, USA"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Ai","family":"Kiyomitsu","sequence":"additional","affiliation":[{"name":"Okinawa Institute of Science and Technology Graduate University, 1919-1 Tancha, Onna-son, Kunigami-gun, Okinawa, 904-0495, Japan"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Yunyi","family":"Shen","sequence":"additional","affiliation":[{"name":"Department of Electrical Engineering and Computer Science, Massachusetts Institute of Technology, Cambridge, MA, USA"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Natalia D.","family":"Orlovsky","sequence":"additional","affiliation":[{"name":"Department of Systems Biology, Harvard Medical School, Boston, MA, USA"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-2280-4611","authenticated-orcid":false,"given":"Tomomi","family":"Kiyomitsu","sequence":"additional","affiliation":[{"name":"Okinawa Institute of Science and Technology Graduate University, 1919-1 Tancha, Onna-son, Kunigami-gun, Okinawa, 904-0495, Japan"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Timothy J.","family":"Mitchison","sequence":"additional","affiliation":[{"name":"Department of Systems Biology, Harvard Medical School, Boston, MA, USA"}],"role":[{"vocabulary":"crossref","role":"author"}]}],"member":"54368","reference":[{"key":"2026081313450746000_2026.08.11.744254v1.1","unstructured":"O\u2019Farrell, P. 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