Characterization of three isotypes of immunoglobulin light chains and T-cell antigen receptor alpha in zebrafish

The zebrafish (Danio rerio) has become a significant model for understandin g the developmental regulation of gene expression and holds considerable po tential for characterizing the development of the immune system. Using a nu mber of different approaches, including heterologous hybridization and shor t-primer PCR, cDNAs for three different classes of light-chain genes were i dentified and characterized. The zebrafish light chains are similar to trou t type 1, trout type 2, and catfish type F, respectively. T-cell antigen re ceptor alpha (TCR alpha) was also identified and characterized. A high prop ortion of unusual transcripts including sterile transcripts, germline VJC t ranscripts, aberrant splice forms, and V-V transcripts were encountered ill the immunoglobulin and TCR cDNAs examined. The light-chain and TCRa TCR lo ci each consist of multiple families of V gene segments, apparent even from the small numbers of cDNAs of each isotype sequenced. The gene sequences r eported provide an essential set of markers of both B- and T-cell lineages that will facilitate investigations of immune system development.