title: Nonagonal cadherins: A new protein family found within the Stramenopiles.
abstract: Cadherins, a group of molecules typically associated with planar cell polarity and Wnt signalling, have been little reported outside of the animal kingdom. Here, we identify a new family of cadherins in the Stramenopiles, termed Nonagonal after their 9 transmembrane passes, which contrast to the one or seven passes found in other known cadherin families. Manual curation and experimental validation reveal two subclasses of nonagonal cadherins, depending on the number of uninterrupted extracellular cadherin (EC) modules presented. Firstly, shorter mono-exonic, unimodular, protein models, with 3 to 12 EC domains occur as duplicate paralogs in the saprotrophic Labyrinthulomycetes Aurantiochytrium limanicum and Schizochytrium aggregatum, the gastrointestinal Blastocystis hominis (Blastocystae) and as a single copy gene in the autotrophic Pelagophyte Aureococcus anophagefferens. Larger, single copy, multi-exonal, tri-modular protein models, with up to 72 EC domain in total, are found in the Oomycete genera Albugo, Phytophthora, Pythium and Eurychasma. No homolog was found in the closely related autotrophic Phaeophyceae (brown algae) or Bacillariophyceae (diatoms), nor in several genera of plant and animal pathogenic oomycetes (Aphanomyces, Saprolegnia and Hyaloperonospora). This potential absence was further investigated by synteny analysis of the genome regions flanking the cadherin gene models, which are found to be highly variable. Novel to this new cadherin family is the presence of intercalated laminin and putative carbohydrate binding in tri-modular oomycete cadherins and at the N-terminus of thraustochytrid proteins. As we were unable to detect any homologs of proteins involved in signalling pathways where other cadherin families are involved, we present a conceptual hypothesis on the function of nonagonal cadherin based around the presence of putative carbohydrate binding domains.
authors: Oceanlab, University of Aberdeen, Newburgh, Aberdeenshire AB41 6AA, United Kingdom; Aberdeen Oomycete Laboratory, Institute of Medical Sciences, University of Aberdeen, Foresterhill, Aberdeen AB25 2ZD, United Kingdom; Culture Collection for Algae and Protozoa, Scottish Marine Institute, Scottish Association for Marine Science, Dunstaffnage, Oban, Argyll PA37 1QA, United Kingdom. Electronic address: kfletcher@ucdavis.edu.
authors: Kyle I G
authors: KIG
authors: Fletcher
authors: Aberdeen Oomycete Laboratory, Institute of Medical Sciences, University of Aberdeen, Foresterhill, Aberdeen AB25 2ZD, United Kingdom. Electronic address: p.vanwest@abdn.ac.uk.
authors: Pieter
authors: P
authors: van West
authors: Culture Collection for Algae and Protozoa, Scottish Marine Institute, Scottish Association for Marine Science, Dunstaffnage, Oban, Argyll PA37 1QA, United Kingdom. Electronic address: claire.gachon@sams.ac.uk.
authors: Claire M M
authors: CMM
authors: Gachon
mesh_terms: D015820:Cadherins / Q000235:genetics*; D000072417:Protein Domains; D013045:Species Specificity; D058009:Stramenopiles / Q000235:genetics*
chemical_list: D015820:Cadherins
keywords: Aureococcus anophagefferens; Blastocystae; Blastocystis hominis; Carbohydrate binding; Cell adhesion; Labyrinthulea; Labyrinthulomycete; Oomycete; Oomycota; Peronosporomycetes; Thraustochytrids; WSC domain