Structure and organization of the T cell receptor alpha chain genes in Atlantic salmon

Abstract

A cDNA fragment of the T cell receptor (TCR) α chain mRNA in Atlantic salmon ( Salmo salar) was amplified by PCR and used as a probe to isolate a full-length clone from a leukocyte cDNA library. Additionally, a genomic lambda clone comprising the TCR α chain constant region (Cα) gene and flanking regions was isolated and partially sequenced. The Cα gene consists of three exons corresponding to the immunoglobulin (Ig) domain, the hinge region and the transmembrane peptide/cytoplasmatic tail, and two exons corresponding to the untranslated tail of the mRNA. Remnants of a transposase gene and a partial duplication of the Cα gene were found nearby the intact gene. One J segment was found 1.5 kb upstream of the Cα gene. Twenty-six other J elements were identified among cDNA fragments covering the V/J/Cα junction. Representatives of five Vα gene families were identified by PCR amplification of genomic DNA fragments. PCR amplification of Cα fragments from another individual revealed a slightly different Cα gene which most likely represents an allelic variant.