title: Novel origin of lamin-derived cytoplasmic intermediate filaments in tardigrades.
abstract: Intermediate filament (IF) proteins, including nuclear lamins and cytoplasmic IF proteins, are essential cytoskeletal components of bilaterian cells. Despite their important role in protecting tissues against mechanical force, no cytoplasmic IF proteins have been convincingly identified in arthropods. Here we show that the ancestral cytoplasmic IF protein gene was lost in the entire panarthropod (onychophoran + tardigrade + arthropod) rather than arthropod lineage and that nuclear, lamin-derived proteins instead acquired new cytoplasmic roles at least three times independently in collembolans, copepods, and tardigrades. Transcriptomic and genomic data revealed three IF protein genes in the tardigrade Hypsibius dujardini, one of which (cytotardin) occurs exclusively in the cytoplasm of epidermal and foregut epithelia, where it forms belt-like filaments around each epithelial cell. These results suggest that a lamin derivative has been co-opted to enhance tissue stability in tardigrades, a function otherwise served by cytoplasmic IF proteins in all other bilaterians.
authors: Department of Zoology, Institute of Biology, University of Kassel, Kassel, Germany.|Animal Evolution and Development, Institute of Biology, University of Leipzig, Leipzig, Germany.
authors: Lars
authors: http://orcid.org/0000-0003-4469-991X
authors: L
authors: Hering
authors: Institute of Biology and Translational Center for Regenerative Medicine, University of Leipzig, Leipzig, Germany.
authors: Jamal-Eddine
authors: JE
authors: Bouameur
authors: Department of Zoology, Institute of Biology, University of Kassel, Kassel, Germany.
authors: Julian
authors: J
authors: Reichelt
authors: Institute of Biology and Translational Center for Regenerative Medicine, University of Leipzig, Leipzig, Germany.
authors: Thomas M
authors: TM
authors: Magin
authors: Department of Zoology, Institute of Biology, University of Kassel, Kassel, Germany.|Animal Evolution and Development, Institute of Biology, University of Leipzig, Leipzig, Germany.
authors: Georg
authors: G
authors: Mayer
mesh_terms: D000818:Animals; D019143:Evolution, Molecular; D020869:Gene Expression Profiling; D023281:Genomics; D007382:Intermediate Filaments / Q000235:genetics / Q000378:metabolism*; D034882:Lamins / Q000378:metabolism*; D058467:Tardigrada / Q000235:genetics / Q000378:metabolism*
chemical_list: D034882:Lamins
keywords: cell biology; cytoskeleton; intermediate filament; lamin; tardigrada