{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"institution":[{"name":"bioRxiv"}],"indexed":{"date-parts":[[2026,7,18]],"date-time":"2026-07-18T17:04:56Z","timestamp":1784394296880,"version":"3.55.0"},"posted":{"date-parts":[[2026,7,16]]},"group-title":"Cell Biology","reference-count":45,"publisher":"openRxiv","license":[{"start":{"date-parts":[[2026,7,16]],"date-time":"2026-07-16T00:00:00Z","timestamp":1784160000000},"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":["R01GM141243"],"award-info":[{"award-number":["R01GM141243"]}],"id":[{"id":"10.13039\/100000057","id-type":"DOI","asserted-by":"crossref"}]}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":[],"accepted":{"date-parts":[[2026,7,16]]},"abstract":"<jats:title>Abstract<\/jats:title>\n                <jats:p>\n                  The ER is a complex network of membranes that inhabits much of the cytoplasm of cells \u2013 however, this network undergoes a massive condensation and rapid remodeling during cell division. In\n                  <jats:italic>Drosophila<\/jats:italic>\n                  cleavage divisions, this results in a tight association of the ER with centrosomes and mitotic spindle poles. Previous work has shown that this relationship between the ER and centrosomes must be finely tuned to enable successful spindle elongation, and that overaccumulation of the ER in these stages can result in failed centrosome maturation. During interphase, the ER exists in tubular and sheet-like arrangements, with a variety of \u201cshaping\u201d proteins enforcing these topologies. Here, we examine the contributions of these ER shaping proteins to the rapid changes that occur during cleavage mitoses in the\n                  <jats:italic>Drosophila<\/jats:italic>\n                  embryo. A screen of ER shaping proteins revealed that disruption of Reep-family proteins leads to mitotic failures at characteristic cleavage stages. Compromising\n                  <jats:italic>ReepA<\/jats:italic>\n                  , the\n                  <jats:italic>Drosophila<\/jats:italic>\n                  ortholog of the Reep1-4 subfamily, had a lesser impact on early embryonic mitoses. However,\n                  <jats:italic>ReepB<\/jats:italic>\n                  (the ortholog of the Reep5-6 subfamily) disruption, significantly affects ER mitotic coat morphologies, resulting in a \u2018frilled ER\u2019 phenotype and a reduction of ER adherence to the spindle space accompanied by division failures. Overexpressing ReepA does not rescue ReepB mitotic or ER morphology defects and instead introduces local condensates of abnormal ER structures. These data suggest that dedicated Reep proteins guide ER mitotic properties at specific early developmental stages. Using a cell-based\n                  <jats:italic>in vitro<\/jats:italic>\n                  analysis of\n                  <jats:italic>Drosophila<\/jats:italic>\n                  Reeps, we identify differential \u201ctubulating\u201d properties of ReepA and ReepB. Together these data suggest that the minutes-scale ER remodeling required for early mitoses is governed by shaping proteins, and that ReepB family members are especially important in some of the most rapid cleavage divisions that occur in early embryo.\n                <\/jats:p>","DOI":"10.64898\/2026.07.15.738729","type":"posted-content","created":{"date-parts":[[2026,7,16]],"date-time":"2026-07-16T14:39:43Z","timestamp":1784212783000},"source":"Crossref","is-referenced-by-count":0,"title":["ER shaping proteins guide spindle elongation and division during rapid cleavage mitoses"],"prefix":"10.64898","author":[{"given":"Katherine R.","family":"Rollins","sequence":"first","affiliation":[{"name":"Department of Biological Sciences, University of Denver, Denver, CO 80208, USA"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Austin R.","family":"Clark","sequence":"additional","affiliation":[{"name":"Department of Biological Sciences, University of Denver, Denver, CO 80208, USA"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Prakriti","family":"Kandel","sequence":"additional","affiliation":[{"name":"Department of Biological Sciences, University of Denver, Denver, CO 80208, USA"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Schuyler B.","family":"van Engelenburg","sequence":"additional","affiliation":[{"name":"Department of Biological Sciences, University of Denver, Denver, CO 80208, USA"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0001-8687-9527","authenticated-orcid":false,"given":"J. Todd","family":"Blankenship","sequence":"additional","affiliation":[{"name":"Department of Biological Sciences, University of Denver, Denver, CO 80208, USA"}],"role":[{"vocabulary":"crossref","role":"author"}]}],"member":"54368","reference":[{"key":"2026071809551213000_2026.07.15.738729v1.1","doi-asserted-by":"publisher","DOI":"10.26508\/lsa.202201540"},{"key":"2026071809551213000_2026.07.15.738729v1.2","doi-asserted-by":"publisher","DOI":"10.1371\/journal.pone.0117859"},{"key":"2026071809551213000_2026.07.15.738729v1.3","doi-asserted-by":"crossref","unstructured":"Brown JB , Boley N , Eisman R , May GE , Stoiber MH , Duff MO , Booth BW , Wen J , Park S , Suzuki AM , Wan KH , Yu C , Zhang D , Carlson JW , Cherbas L , Eads BD , Miller D , Mockaitis K , Roberts J , Davis CA , Frise E , Hammonds AS , Olson S , Shenker S , Sturgill D , Samsonova AA , Weiszmann R , Robinson G , Hernandez J , Andrews J , Bickel PJ , Carninci P , Cherbas P , Gingeras TR , Hoskins RA , Kaufman TC , Lai EC , Oliver B , Perrimon N , Graveley BR , Celniker SE . Diversity and dynamics of the Drosophila transcriptome. 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