{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"institution":[{"name":"bioRxiv"}],"indexed":{"date-parts":[[2026,7,30]],"date-time":"2026-07-30T12:44:51Z","timestamp":1785415491075,"version":"3.56.0"},"posted":{"date-parts":[[2025,3,13]]},"group-title":"Developmental Biology","reference-count":74,"publisher":"openRxiv","license":[{"start":{"date-parts":[[2025,3,13]],"date-time":"2025-03-13T00:00:00Z","timestamp":1741824000000},"content-version":"vor","delay-in-days":0,"URL":"http:\/\/creativecommons.org\/licenses\/by-nc-nd\/4.0\/"}],"funder":[{"award":["GM117502"],"award-info":[{"award-number":["GM117502"]}],"id":[{"id":"https:\/\/ror.org\/04q48ey07","id-type":"ROR","asserted-by":"publisher"}]},{"award":["GM158065"],"award-info":[{"award-number":["GM158065"]}],"id":[{"id":"https:\/\/ror.org\/04q48ey07","id-type":"ROR","asserted-by":"publisher"}]}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":[],"accepted":{"date-parts":[[2026,6,2]]},"abstract":"<jats:title>ABSTRACT<\/jats:title>\n                <jats:p>\n                  Germline cysts, or interconnected groups of germ cells, promote the synchronization of gamete development in vertebrates and invertebrates. In the\n                  <jats:italic>Drosophila<\/jats:italic>\n                  ovary, cyst formation is coordinated by the fusome, a unique endoplasmic reticulum-like organelle. Although many structural components of the fusome have been characterized, little is known about the genetic factors that control fusome growth and distribution between germ cells. Here, we identify the \u03b2-importin,\n                  <jats:italic>Tnpo-SR<\/jats:italic>\n                  , as an important regulator of fusome morphogenesis in germline stem cells (GSCs) and their dividing daughters. Although Tnpo-SR does not aggregate at fusomes or centrosomes,\n                  <jats:italic>Tnpo-SR<\/jats:italic>\n                  null mutants fail to form proper fusomes and knock-down of\n                  <jats:italic>Tnpo-SR<\/jats:italic>\n                  reduces fusome accumulation, ultimately leading to cyst fragmentation and improper numbers of germ cells within an egg chamber.\n                  <jats:italic>Tnpo-SR<\/jats:italic>\n                  depletion disrupts microtubule organization during interphase and sub-cellular localization of the microtubule associated protein Asp. However, overexpression of\n                  <jats:italic>asp<\/jats:italic>\n                  is not sufficient to restore fusome size or cyst architecture when\n                  <jats:italic>Tnpo-SR<\/jats:italic>\n                  is depleted, suggesting that\n                  <jats:italic>Tnpo-SR<\/jats:italic>\n                  -dependent regulation of\n                  <jats:italic>asp<\/jats:italic>\n                  does not solely control fusome morphogenesis. Instead, we find that restoring fusome size by overexpressing the core fusome component\n                  <jats:italic>hu-li tai shao<\/jats:italic>\n                  or the polarity factor\n                  <jats:italic>Par3\/bazooka<\/jats:italic>\n                  is sufficient to restore fusome area in\n                  <jats:italic>Tnpo-SR<\/jats:italic>\n                  -depleted GSCs. Moreover, restoration of fusome area in the absence of\n                  <jats:italic>Tnpo-SR<\/jats:italic>\n                  also rescues cyst organization and oocyte specification, suggesting that\n                  <jats:italic>Tnpo-SR<\/jats:italic>\n                  functions upstream of fusome structural component production. Taken together, these data functionally link nuclear import\/export machinery to fusome morphogenesis during\n                  <jats:italic>Drosophila<\/jats:italic>\n                  germline cyst development.\n                <\/jats:p>\n                <jats:sec>\n                  <jats:title>ARTICLE SUMMARY<\/jats:title>\n                  <jats:p>\n                    The fusome plays a key role in cyst formation in the\n                    <jats:italic>Drosophila<\/jats:italic>\n                    ovarian germline, yet regulation of fusome growth and distribution between germ cells after mitosis remains understudied. Through loss-of-function analyses, the authors identify\n                    <jats:italic>Tnpo-SR<\/jats:italic>\n                    as a novel regulator of fusome morphogenesis.\n                    <jats:italic>Tnpo-SR<\/jats:italic>\n                    depletion reduces the core fusome structural component Hts in germline stem cells (GSCs) and disrupts microtubule organization and nucleation. Overexpression of\n                    <jats:italic>Hts<\/jats:italic>\n                    or\n                    <jats:italic>Par3\/bazooka<\/jats:italic>\n                    in\n                    <jats:italic>Tnpo-SR<\/jats:italic>\n                    -depleted GSCs restores fusome size, which in turn rescues cyst organization and oocyte specification. These findings establish Tnpo-SR as an upstream regulator of Hts during fusome morphogenesis.\n                  <\/jats:p>\n                <\/jats:sec>","DOI":"10.1101\/2025.03.10.642432","type":"posted-content","created":{"date-parts":[[2025,3,13]],"date-time":"2025-03-13T20:55:26Z","timestamp":1741899326000},"source":"Crossref","is-referenced-by-count":0,"title":["A \u03b2-importin promotes fusome growth and distribution in\n                  <i>Drosophila<\/i>\n                  ovarian germ cells"],"prefix":"10.64898","author":[{"ORCID":"https:\/\/orcid.org\/0000-0001-5450-6726","authenticated-orcid":false,"given":"Amanda M.","family":"Powell","sequence":"first","affiliation":[{"name":"Department of Biology, East Carolina University, Greenville, NC 27858, USA"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Anna E.","family":"Williams","sequence":"additional","affiliation":[{"name":"Department of Biology, East Carolina University, Greenville, NC 27858, USA"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-6934-9302","authenticated-orcid":false,"given":"Elizabeth T.","family":"Ables","sequence":"additional","affiliation":[{"name":"Department of Biology, East Carolina University, Greenville, NC 27858, USA"}],"role":[{"vocabulary":"crossref","role":"author"}]}],"member":"54368","reference":[{"key":"2026060501100528000_2025.03.10.642432v2.1","doi-asserted-by":"publisher","DOI":"10.1242\/dev.088583"},{"key":"2026060501100528000_2025.03.10.642432v2.2","doi-asserted-by":"publisher","DOI":"10.1091\/mbc.E02-02-0102"},{"key":"2026060501100528000_2025.03.10.642432v2.3","doi-asserted-by":"publisher","DOI":"10.1007\/978-3-319-44820-6"},{"key":"2026060501100528000_2025.03.10.642432v2.4","doi-asserted-by":"publisher","DOI":"10.1091\/mbc.E02-06-0346"},{"key":"2026060501100528000_2025.03.10.642432v2.5","doi-asserted-by":"crossref","unstructured":"Barr J , Diegmiller R , Colonnetta MM , Ke W , Imran Alsous J , Stern T , Shvartsman SY and Schedl P (2024) To be or not to be: orb, the fusome and oocyte specification in Drosophila . 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