We performed 5′ RACE using degenerate primers based on a conserved C domain amino acid sequence to isolate putative dromedary TCRG chain cDNA clones. A total of 20 cDNA clones were selected, and two groups of clones were identified which shared PD0325901 mw almost identical C region sequences (nucleotide identity of 89%), which were respectively named TCRGC2 and TCRGC1 (Supporting Information Table 1). A BLAST search showed that the clones shared significant identity with known TCR γ chains, the best match being with the TCR γ chain of artiodactyls (ruminants and pig). The complete

sequences of the C regions were assembled using cDNA clones from 3′ RACE. A comparison of the deduced amino acid sequence of the two assembled

C regions with sheep and human sequences, as well as the boundaries of their conserved extracellular domain (C-DOMAIN), connecting (CO), transmembrane (TM), and cytoplasmatic (CY) domains, is shown in Figure 1A. Considering the exon organization of the ovine and human C regions, we inferred that both the dromedary C regions keep a connecting region encoded by three different exons, as is observed in the sheep TCRGC2, this website TCRGC4, and TCRGC6 genes [15] and in the polymorphic human TCRGC2 gene [2, 16]. The two cysteines involved in the intrachain disulfide bond (positions 23 and 104 according to the IMGT unique numbering [17]) and those involved in the interchain disulfide bond are conserved, as well as the lysine (Lys K) amino acid in the TM region required for interaction with CD3γ. Furthermore two TCRGV genes and two distinct TCRGJ genes were identified within the variable domain of the cDNA clones. The TCRGV genes were classified in two distinct TCRGV1 and TCRGV2 subgroups. Sequence comparison with the available database entries indicates a high level of similarity Immune system with the ovine TCRGV6-1 and pig TCRGV5-1 functional genes (Fig. 1B), whereas its most strictly related counterpart in human (the TCRGVA gene) is a pseudogene. Similarly, the TCRGV1 gene subgroup has the highest level of similarity with TCRGV genes of artiodactyls (ovine TCRGV9-1 and

pig TCRGV6-1) (Fig. 1B). The sequence analysis of the isolated cDNA clones suggests the presence of two TCRG cassettes. Dromedary lung DNA was purified to perform sequencing of the germline TCRG locus. Both genomic PCR and Genome Walker DNA walking strategies were used. The sequence was assembled from ten PCR products and three chomosome walking fragments and in most cases was derived from at least two independent products. A gap in the genomic sequence exists between TCRGJ1-1 and TCRGC1. However, we identified a partially assembled lama (Lama pacos) genomic scaffold (acc. ABRR01332756.1) similar to dromedary TCRG1 cassette (see Materials and Methods). We found out that another TCRGJ gene (TCRGJ1-2) is present downstream of TCRGJ1-1 in the lama genome.