Immunogenetics

, Volume 53, Issue 12, pp 1055–1064 | Cite as

Complement in urochordates: cloning and characterization of two C3-like genes in the ascidian Ciona intestinalis

  • Rita Marino
  • Yuko Kimura
  • Rosaria De Santis
  • John D. Lambris
  • Maria Pinto
Original Paper

Abstract

The recent identification of complement components in deuterostome invertebrates has indicated the presence of a complement system operating via an alternative pathway in echinoderms and tunicates and via a MBL-mediated pathway thus far identified only in tunicates. Here, we report the isolation of two C3-like genes, CiC3-1 and CiC3-2, from blood cell total RNA of the ascidian Ciona intestinalis. The deduced amino acid sequences of both Ciona C3-like proteins exhibit a canonical processing site for α and β chains, a thioester site with an associated catalytic histidine and a convertase cleavage site, thus showing an overall similarity to the other C3 molecules already characterized. Southern blotting analysis indicated that each gene is present as a single copy per haploid genome. In situ hybridization experiments showed that both CiC3-1 and CiC3-2 are expressed in one type of blood cell, the compartment cells. Two polyclonal antibodies, raised against two deduced peptide sequences in the α chain of CiC3-1 and CiC3-2, allowed the identification by Western blot of a single band in the blood serum, of about Mr 150,000. A phylogenetic tree, based on the alignment of CiC3-1 and CiC3-2 with molecules of the α2-macroglobulin superfamily, indicated that the Ciona C3s form a cluster with Halocynthia roretzi C3. The phylogenetic analysis also suggested that the duplication event from which the CiC3-1 and CiC3-2 genes originated occurred in the urochordate lineage after the separation of the Halocynthia and Ciona ancestor.

Ascidians Complement evolution C3 Thioester 

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Copyright information

© Springer-Verlag 2002

Authors and Affiliations

  • Rita Marino
    • 1
  • Yuko Kimura
    • 2
  • Rosaria De Santis
    • 1
  • John D. Lambris
    • 2
  • Maria Pinto
    • 1
  1. 1.Laboratory of Cell Biology, Stazione Zoologica "Anton Dohrn", Villa Comunale, 80121 NaplesItaly
  2. 2.Department of Pathology and Laboratory Medicine, University of Pennsylvania, 401 Stellar Chance, Philadelphia, PA 19104USA

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