Identification of diversified genes that contain immunoglobulin-like variable regions in a protochordate

Nat Immunol. 2002 Dec;3(12):1200-7. doi: 10.1038/ni849. Epub 2002 Nov 4.


The evolutionary origin of adaptive immune receptors is not understood below the phylogenetic level of the jawed vertebrates. We describe here a strategy for the selective cloning of cDNAs encoding secreted or transmembrane proteins that uses a bacterial plasmid (Amptrap) with a defective beta-lactamase gene. This method requires knowledge of only a single target motif that corresponds to as few as three amino acids; it was validated with major histocompatibility complex genes from a cartilaginous fish. Using this approach, we identified families of genes encoding secreted proteins with two diversified immunoglobulin-like variable (V) domains and a chitin-binding domain in amphioxus, a protochordate. Thus, multigenic families encoding diversified V regions exist in a species lacking an adaptive immune response.

Publication types

  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Amino Acid Sequence
  • Animals
  • Echinodermata / genetics
  • Echinodermata / immunology
  • Genes, Immunoglobulin*
  • Immunity / genetics*
  • Immunoglobulin Variable Region / genetics*
  • Molecular Sequence Data
  • Multigene Family*
  • Phylogeny
  • Receptors, Immunologic / genetics


  • Immunoglobulin Variable Region
  • Receptors, Immunologic

Associated data

  • GENBANK/AF520472
  • GENBANK/AF520473
  • GENBANK/AF520474
  • GENBANK/AF520475
  • GENBANK/AF520476
  • GENBANK/AF532182
  • GENBANK/AF532183
  • RefSeq/NP_004039
  • RefSeq/NP_006056
  • RefSeq/NP_006669
  • RefSeq/NP_033865
  • RefSeq/NP_112543
  • RefSeq/NP_476579
  • RefSeq/NP_571238
  • RefSeq/NP_571721