Structural molecular components of septate junctions in cnidarians point to the origin of epithelial junctions in eukaryotes

Mol Biol Evol. 2015 Jan;32(1):44-62. doi: 10.1093/molbev/msu265. Epub 2014 Sep 21.


Septate junctions (SJs) insure barrier properties and control paracellular diffusion of solutes across epithelia in invertebrates. However, the origin and evolution of their molecular constituents in Metazoa have not been firmly established. Here, we investigated the genomes of early branching metazoan representatives to reconstruct the phylogeny of the molecular components of SJs. Although Claudins and SJ cytoplasmic adaptor components appeared successively throughout metazoan evolution, the structural components of SJs arose at the time of Placozoa/Cnidaria/Bilateria radiation. We also show that in the scleractinian coral Stylophora pistillata, the structural SJ component Neurexin IV colocalizes with the cortical actin network at the apical border of the cells, at the place of SJs. We propose a model for SJ components in Cnidaria. Moreover, our study reveals an unanticipated diversity of SJ structural component variants in cnidarians. This diversity correlates with gene-specific expression in calcifying and noncalcifying tissues, suggesting specific paracellular pathways across the cell layers of these diploblastic animals.

Keywords: Capsaspora; Claudin; Contactin; Coracle; DSCAM; Epitheliozoa; MAGUK; Monosiga; Na+/K+ ATPase transporter; Nbl4; Neurexin; Neuroglian; corals; ctenophores; para-cellular pathway; permselectivity; poriferans.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Cnidaria / genetics
  • Cnidaria / metabolism*
  • Computational Biology / methods
  • Epithelial Cells / physiology*
  • Eukaryota / cytology*
  • Eukaryota / genetics
  • Eukaryota / metabolism
  • Evolution, Molecular
  • Genome
  • Intercellular Junctions / genetics
  • Intercellular Junctions / metabolism*
  • Models, Genetic
  • Phylogeny
  • Tight Junction Proteins / genetics*
  • Tight Junction Proteins / metabolism


  • Tight Junction Proteins