Concerted Evolution of the Immunoglobulin VH Multigene Family

Abstract

Evolutionary features of the immunoglobulin variable region heavy chain (VH) multigene family were discussed with special reference to the concerted evolution. In particular, a phylogenetic tree for the DNA sequences of 16 mouse and five human germline genes was constructed. This tree indicates that all genes in this family have undergone substantial evolutionary divergence. The most closely related genes so far identified in the mouse genome seem to have diverged about 6 million years (MY) ago, whereas the most distantly related genes diverged about 300 MY ago. This suggests that gene duplication caused by unequal crossing-over or gene conversion occurs very slowly in this gene family. The rate of occurrence of gene duplication in the VH gene family has been estimated to be 5×10^-7 per gene per year, which seems to be at least about 100 times lower than that for the rRNA gene family. This low rate of concerted evolution in the VH gene family helps retain intergenic genetic variability that in turn contributes to antibody diversity.