{
  "id": 5006078,
  "title": "Rapid repurposing of microvillar content drives a flagellate-to-amoeboid switch in the closest relative of animals",
  "url": "https://urgent.news/2026/09/01/rapid-repurposing-of-microvillar-content-drives-a-flagellate-to",
  "topic": "science",
  "section": "Science",
  "published": "2026-09-01T00:00:00.000Z",
  "source": {
    "name": "bioRxiv",
    "slug": "biorxiv",
    "url": "https://www.biorxiv.org/content/10.64898/2026.08.28.747835v1?rss=1"
  },
  "original_language": "en",
  "account": "Choanoflagellates, the closest living relatives to animals, are typically known for their flagellum-based swimming, but they can transform into an amoeboid form when confined. This transformation, which involves switching from a motility mode reliant on a flagellum to one using an actin cortex, has been observed in Salpingoeca rosetta. Live imaging, ultrastructural expansion microscopy, and cryo-electron tomography were used to reveal that this switch is driven by rapid, cell-wide cytoskeletal remodeling. Under unconfined conditions, these organisms have an apical flagellum and cortical microtubules, with actin primarily concentrated in microvilli. When confined, calcium released from intracellular stores leads to microvillar retraction and absorption of this material into the cell body. This process includes the remodeling of internalized actin and repurposing associated proteins, which ultimately facilitates the formation of a new actin cortex necessary for amoeboid motility. Meanwhile, cortical microtubules disassemble, and the reabsorbed microvillar plasma membrane expands the surface area of the cell body, enabling it to flatten under confinement. Cryo-electron tomography shows a stepwise actin reorganization from microvillar bundles to a cortical contractile meshwork composed of bundles and scattered filaments. This study highlights the remarkable ultrastructural plasticity of choanoflagellates and suggests that microvilli serve as a reservoir of membrane and cytoskeleton components, enabling cell phenotypic transitions.",
  "summary": "Animal cells extensively remodel their cytoskeleton during differentiation and can notably switch between two major motility modes: flagellum-based swimming and actin-based crawling. We previously showed that choanoflagellates, the closest living relatives of animals and classically viewed as obligate flagellated swimmers, can retract their collar complex and adopt an amoeboid form within seconds…",
  "key_points": [],
  "editors_take": null,
  "illustration": null,
  "coverage": {
    "outlets": 1,
    "also_reported_by": []
  },
  "ai_generated": true,
  "disclaimer": "Summaries, key points and the editor’s take are written by software from other outlets’ reporting and may contain errors — always check the linked original."
}