Preprint Article Version 1 Preserved in Portico This version is not peer-reviewed

The Genomic Organisation of the TRA/TRD Locus Validates the Peculiar Characteristics of Dromedary δ-Chain Expression

Version 1 : Received: 12 March 2021 / Approved: 15 March 2021 / Online: 15 March 2021 (12:32:41 CET)

A peer-reviewed article of this Preprint also exists.

Massari, S.; Linguiti, G.; Giannico, F.; D’Addabbo, P.; Ciccarese, S.; Antonacci, R. The Genomic Organisation of the TRA/TRD Locus Validates the Peculiar Characteristics of Dromedary δ-Chain Expression. Genes 2021, 12, 544. Massari, S.; Linguiti, G.; Giannico, F.; D’Addabbo, P.; Ciccarese, S.; Antonacci, R. The Genomic Organisation of the TRA/TRD Locus Validates the Peculiar Characteristics of Dromedary δ-Chain Expression. Genes 2021, 12, 544.

Journal reference: Genes 2021, 12, 544
DOI: 10.3390/genes12040544

Abstract

The role of γδ T cells in vertebrate immunity is still an unsolved puzzle. Species such as humans and mice display a low percentage of these T lymphocytes (i.e., “γδ low species”) with a restricted diversity of γδ T cell receptors (TR). Conversely, artiodactyl species (i.e., “γδ high species”) ac-count for a high proportion of γδ T cells with large γ and δ chain repertoires. The genomic organisation of the TR γ (TRG) and δ (TRD) loci has been determined in sheep and cattle, noting that a wide number of germline genes that encode for γ and δ chains characterise their genomes. Taking advantage from the current improved version of the genome assembly, we have investigated the genomic structure and gene content of the dromedary TRD locus, which, as in the other mammalian species, is nested within the TR alpha (TRA) genes. The most remarkable finding was the identification of a very limited number of variable germline genes (TRDV) compared to sheep and cattle, which supports our previous expression analyses for which the somatic hypermutation mechanism is able to enlarge and diversify the primary repertoire of dromedary δ chains. Furthermore, the comparison between genomic and expressed sequences reveals that D genes, up to four incorporated in a transcript, greatly contribute to the increased diversity of the dromedary δ chain antigen binding-site.

Subject Areas

γδ T cell; T cell receptor; TRA/TRD locus; Variable, Diversity, Joining and Constant genes; complementarity determining region-3; δ chain; somatic hypermutation; Camelidae

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