Evolution of V genes from the TRV loci of mammals

Abstract

Information concerning the evolution of T lymphocyte receptors (TCR) can be deciphered from that part of the molecule that recognizes antigen presented by major histocompatibility complex (MHC), namely the variable (V) regions. The genes that code for these variable regions are found within the TCR loci. Here, we describe a study of the evolutionary origin of V genes that code for the α and β chains of the TCR loci of mammals. In particular, we demonstrate that most of the 35 TRAV and 25 TRBV conserved genes found in Primates are also found in other Eutheria, while in Marsupials, Monotremes, and Reptiles, these genes diversified in a different manner. We also show that in mammals, all TRAV genes are derived from five ancestral genes, while all TRBV genes originate from four such genes. In Reptiles, the five TRAV and three out of the four TRBV ancestral genes exist, as well as other V genes not found in mammals. We also studied the TRGV and TRDV loci from all mammals, and we show a relationship of the TRDV to the TRAV locus throughout evolutionary time.

A comprehensive analysis of the germline and expressed TCR repertoire in White Peking duck

“…The Ig V genes undergo more pronounced birth/death processes, thereby permitting the frequent duplication of specific V subgroups that could directly recognize rapidly changing antigens in the external environment. By contrast, the V genes from the TCRα and TCRβ loci, which consist of multiple subgroups ( Table 2 ) with relatively low duplication permissiveness throughout evolution, appeared to have undergone a co-evolution process with MHC molecules, resulting in natural evolutionary pressures 42 43 44 . As shown in Table 2 , the most striking feature of duck Vα and Vβ genes is the presence of fewer subgroups in comparison to mammals.…”

Iterative Variable Gene Discovery from Whole Genome Sequencing with a Bootstrapped Multiresolution Algorithm

“…These gene sequences also provide detailed clues of repertoire adaptation and divergence amongst orders. In primates, evolutionary conserved TCR clades were identified [16] that were later seen to exist throughout all present-day mammals [17].…”