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 M r 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.
Similar content being viewed by others
Author information
Authors and Affiliations
Additional information
Electronic Publication
Rights and permissions
About this article
Cite this article
Marino, R., Kimura, Y., De Santis, R. et al. Complement in urochordates: cloning and characterization of two C3-like genes in the ascidian Ciona intestinalis . Immunogenetics 53, 1055–1064 (2002). https://doi.org/10.1007/s00251-001-0421-9
Received:
Revised:
Published:
Issue Date:
DOI: https://doi.org/10.1007/s00251-001-0421-9