The immunoglobulin heavy-chain locus in zebrafish: identification and expression of a previously unknown isotype, immunoglobulin Z

Nat Immunol. 2005 Mar;6(3):295-302. doi: 10.1038/ni1166. Epub 2005 Jan 30.


The only immunoglobulin heavy-chain classes known so far in teleosts have been mu and delta. We identify here a previously unknown class, immunoglobulin zeta, expressed in zebrafish and other teleosts. In the zebrafish heavy-chain locus, variable (V) gene segments lie upstream of two tandem diversity, joining and constant (DJC) clusters, resembling the mouse T cell receptor alpha (Tcra) and delta (Tcrd) locus. V genes rearrange to (DJC)(zeta) or to (DJC)(mu) without evidence of switch rearrangement. The zebrafish immunoglobulin zeta gene (ighz) and mouse Tcrd, which are proximal to the V gene array, are expressed earlier in development. In adults, ighz was expressed only in kidney and thymus, which are primary lymphoid organs in teleosts. This additional class adds complexity to the immunoglobulin repertoire and raises questions concerning the evolution of immunoglobulins and the regulation of the differential expression of ighz and ighm.

Publication types

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

MeSH terms

  • Animals
  • Base Sequence
  • Fishes / genetics
  • Gene Rearrangement
  • Genes, Immunoglobulin*
  • Immunoglobulin Heavy Chains / genetics*
  • Immunoglobulin Heavy Chains / metabolism
  • Immunoglobulin Isotypes / genetics
  • Immunoglobulin Isotypes / metabolism
  • Immunoglobulin delta-Chains / genetics
  • Immunoglobulin mu-Chains / genetics
  • Molecular Sequence Data
  • Phylogeny
  • Zebrafish / genetics*
  • Zebrafish / immunology*
  • Zebrafish Proteins / genetics*
  • Zebrafish Proteins / metabolism


  • Immunoglobulin Heavy Chains
  • Immunoglobulin Isotypes
  • Immunoglobulin delta-Chains
  • Immunoglobulin mu-Chains
  • Zebrafish Proteins
  • immunoglobulin zeta, zebrafish

Associated data

  • GENBANK/BX510335
  • GENBANK/BX548009
  • GENBANK/BX649502