Evolution of immunogenetic components encoding ultralong CDR H3

We examined genomes of twelve species of Bovidae to determine when ultralong-encoding IGHV and IGHD gene segments evolved. We located the 8-bp duplication encoding the unique TTVHQ motif in ultralong IGHV segments in six Bovid species (cattle, zebu, wild yak, domestic yak, American bison, and domestic gayal), but we did not find evidence of the duplication in species beyond theBos andBison genera. Additionally, we analyzed mRNA from bison spleen and identified a rich repertoire of expressed ultralong CDR H3 antibody mRNA, suggesting that bison use ultralong IGHV transcripts in their host defense. We found ultralong-encoding IGHD gene segments in all the same species except domestic yak, but again not beyond theBos andBison clade. Thus, the duplication event leading to this ultralong-encoding IGHV gene segment and the emergence of the ultralong-encoding IGHD gene segment appears to have evolved in a common ancestor of theBos andBison genera 5 –10 million years ago.

Source: Immunogenetics - April 21, 2023 Category: Genetics & Stem Cells Source Type: research