The expansion of the TRB and TRG genes in domestic goats ( Capra hircus) is characteristic of the ruminant species
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RESEARCH ARTICLE
Open Access
The expansion of the TRB and TRG genes in domestic goats (Capra hircus) is characteristic of the ruminant species Francesco Giannico1, Serafina Massari2, Anna Caputi Jambrenghi3, Adriano Soriano4, Angela Pala4, Giovanna Linguiti4, Salvatrice Ciccarese4 and Rachele Antonacci4*
Abstract Background: Goats (Capra hircus), one of the first domesticated species, are economically important for milk and meat production, and their broad geographical distribution reflects their successful adaptation to diverse environmental conditions. Despite the relevance of this species, the genetic research on the goat traits is limited compared to other domestic species. Thanks to the latest goat reference genomic sequence (ARS1), which is considered to be one of the most continuous assemblies in livestock, we deduced the genomic structure of the T cell receptor beta (TRB) and gamma (TRG) loci in this ruminant species. Results: Our analyses revealed that although the organization of the goat TRB locus is broadly similar to that of the other artiodactyl species, with three in-tandem D-J-C clusters located at the 3′ end, a complex and extensive series of duplications have occurred in the V genes at the 5′ end, leading to a marked expansion in the number of the TRBV genes. This phenomenon appears to be a feature of the ruminant lineage since similar gene expansions have also occurred in sheep and cattle. Likewise, the general organization of the goat TRG genes is typical of ruminant species studied so far, with two paralogous TRG loci, TRG1 and TRG2, located in two distinct and distant positions on the same chromosome as result of a split in the ancestral locus. Each TRG locus consists of reiterated V-J-J-C cassettes, with the goat TRG2 containing an additional cassette relative to the corresponding sheep and cattle loci. Conclusions: Taken together, these findings demonstrate that strong evolutionary pressures in the ruminant lineage have selected for the development of enlarged sets of TRB and TRG genes that contribute to a diverse T cell receptor repertoire. However, differences observed among the goat, sheep and cattle TRB and TRG genes indicate that distinct evolutionary histories, with independent expansions and/or contractions, have also affected each ruminant species. Keywords: T cell receptor, TRB locus, TRG locus, TRB genes, TRG genes, Goat genome, Ruminants, ImMunoGeneTics database
* Correspondence: [email protected] 4 Department of Biology, University of Bari “Aldo Moro”, 70124 Bari, Italy Full list of author information is available at the end of the article © The Author(s). 2020 Open Access This article is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons licence, and indicate if changes were made. The images or other third party material in this arti
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