Abstract
Molecular studies in human, mouse, rat, and rabbit have demonstrated that the region of genomic DNA containing TCR C region genes has been strongly conserved during evolution. To investigate the degree of conservation of this region within the primate lineage we have undertaken analysis of the TCR constant region genes in two non-human primate species Pan troglodytes (chimpanzee) and Macaca mulatta (rhesus monkey). Constant regions of TCR beta-chains were cloned and sequenced from cDNA derived from peripheral blood T cells of healthy chimpanzees and rhesus monkeys. Two closely related C beta genes were characterized in each species corresponding to human C beta 1 and C beta 2. The chimpanzee/human similarity is greater than the rhesus monkey/human similarity as is expected from phylogenetic relationships. The amino acid sequences of corresponding C beta genes are identical between chimpanzee and human although synonymous substitutions are present at the nucleotide level. Two distinct monkey C beta 1 sequences were obtained. RFLP studies using genomic DNA from individuals of both species indicated the presence of only two C beta genes in each species. It is therefore likely that the rhesus monkey from which the sequence data are derived has a polymorphic C beta locus, which was also subsequently demonstrated in several other monkeys. Analysis of sequence data suggests that some nucleotide substitutions occurred after the chimpanzee/human line split from the rhesus monkey line approximately 25 million yr ago. These data also support the theory that specific mechanisms exist to reduce diversity in putative exon 1. Variable RFLP profiles indicated the presence of C beta polymorphism in chimpanzees and rhesus monkeys. There was also evidence for a homozygous deletion of a C beta gene in one monkey, represented by the absence of one band for each digest when compared to the band patterns of other monkeys. Variable intensities of the deletable band in other individuals suggest other monkeys may be heterozygous for this deletion. Thus rhesus monkeys demonstrate RFLP, coding sequence, and C beta gene deletion polymorphisms, with chimpanzees also demonstrating RFLP polymorphisms of C beta.
