title: Expression and genomic analyses of Camelus dromedarius T cell receptor delta (TRD) genes reveal a variable domain repertoire enlargement due to CDR3 diversification and somatic mutation.
abstract: By a combination of rapid amplification of cDNA ends (RACE) and reverse transcription-polymerase chain reaction (RT-PCR) we identified three T cell receptor delta variable (TRDV) subgroups and five joining (TRDJ) genes expressed in spleen, tonsils and blood of Camelus dromedarius. We provide evidence that the high diversity in sequence and length of the third complementarity determining region (CDR3) is a major component of the TR delta chain variability. Moreover, the identification of the corresponding germline genes allowed us to find out for the first time in a mammalian organism that productively rearranged TRDV genes undergo somatic mutation: the mutation rate of the analysed TRDV4 region is 0.013 per base pair in spleen and 0.009 in blood. The point mutations are scattered throughout the length of the variable domain from framework region FR1 to FR4. This random distribution of the amino acid changes, instead of its CDR clustering observed in immunoglobulins (IG), indicates that somatic mutation in dromedary, while contributing to the development of the TRDV repertoire, is not under antigen selection.
authors.affiliation: Department of Genetics and Microbiology, University of Bari, via Amendola 165/A 70126 Bari, Italy.
authors.forename: Rachele
authors.initials: R
authors.lastname: Antonacci
authors.forename: Micaela
authors.initials: M
authors.lastname: Mineccia
authors.forename: Marie-Paule
authors.initials: MP
authors.lastname: Lefranc
authors.forename: Hassan M E
authors.initials: HM
authors.lastname: Ashmaoui
authors.forename: Cecilia
authors.initials: C
authors.lastname: Lanave
authors.forename: Barbara
authors.initials: B
authors.lastname: Piccinni
authors.forename: Graziano
authors.initials: G
authors.lastname: Pesole
authors.forename: Mohamed S
authors.initials: MS
authors.lastname: Hassanane
authors.forename: Serafina
authors.initials: S
authors.lastname: Massari
authors.forename: Salvatrice
authors.initials: S
authors.lastname: Ciccarese
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D002162:Camelus / Q000235:genetics* / Q000276:immunology*; D022801:Complementarity Determining Regions / Q000235:genetics*; D016694:Gene Rearrangement, delta-Chain T-Cell Antigen Receptor; D019675:Genes, T-Cell Receptor gamma; D008969:Molecular Sequence Data; D014066:Palatine Tonsil / Q000166:cytology / Q000276:immunology; D010802:Phylogeny; D017354:Point Mutation; D017434:Protein Structure, Tertiary; D016692:Receptors, Antigen, T-Cell, gamma-delta / Q000737:chemistry*; D020133:Reverse Transcriptase Polymerase Chain Reaction; D016415:Sequence Alignment; D017422:Sequence Analysis, DNA; D020539:Sequence Analysis, Protein; D013154:Spleen / Q000166:cytology / Q000276:immunology
chemical_list: D022801:Complementarity Determining Regions; D016692:Receptors, Antigen, T-Cell, gamma-delta