Characterization of major histocompatibility complex class I allele polymorphisms in common marmosets

Abstract

Currently, little information is available for major histocompatibility complex (MHC)-I that conditions the T-cell response of marmosets. In this study, 471 clones of MHC-I cDNA sequences were isolated from 12 marmosets. Twenty full-length sequences of class I G (Caja-G) alleles were obtained from these marmosets, 15 of them were novel. Among these 20 Caja-G alleles, 10 were found in individual animals while the rests were in two to four marmosets, but none was common to all animals. Ten marmosets possessed one to three Caja-G alleles, and two marmosets carried five or six alleles, which suggested that the Caja-G locus was duplicated in marmoset's genome. The high polymorphisms of Caja-G sequences provided important information helpful for understanding the cellular immune response in virus-infected marmosets.

Gene conversion of the major histocompatibility complex class I Caja‐G in common marmosets (Callithrix jacchus)

“…Duplication of the MHC class I Caja‐B segment has already been observed, supporting the possibility of locus duplication, although further studies are required for verification. Contrary to previous publications, the Caja‐G alleles Caja‐G*07:01:01 , Caja‐G*08:01 , Caja‐G*08:23 and Caja‐G*18:04 were present in the majority of animals, seeming to have priority over others because of their high occurrence in individual unrelated animals. It can be speculated that 40 years of breeding that started from a relatively small group of breeding pairs in Europe might propagate such a phenomenon as major alleles.…”

“…In the studied group of marmosets, 30 new Caja‐G alleles were detected with a high amount of variant alleles from different phylogenetic lineages, revealing high diversity at the nucleotide as well as the amino acid level. As a result of naturally occurring bone marrow chimerism, the presence of up to 10 functional Caja‐G alleles and the similar appearance of some allele combinations indicate that the Caja‐G locus may have been subjected to expansion, which corresponds with recently published data . To limit the risk of cross‐contamination, samples were taken at different time‐points and by the use of sterile single‐use syringes.…”

“…As a result of naturally occurring bone marrow chimerism, the presence of up to 10 functional Caja-G alleles and the similar appearance of some allele combinations indicate that the Caja-G locus may have been subjected to expansion, which corresponds with recently published data. 27,29 To Table 3. Comparison of Risler index amino acid substitutions of Caja-G*08:01, Caja-G*08:23, Caja-G*07:01:01, Caja-G*18:04…”

“…The different lineages show abundant rates of polymorphism, which corresponds with the results of former studies. [27][28][29] Interestingly, the four alleles with the highest occurrence are clustered into three different lineages (Caja-G*07, Caja-G*18, Caja-G*08) leading to the assumption of a high variability on amino acid and therefore also on the nucleotide level.…”

“…27 Whereas only limited variability of the HLA-G has been observed, 13,34,35 in contrast to classical MHC class I genes, the number of recently discovered variant Caja-G alleles from different lineages is still growing. 18,[27][28][29] Even though the phylogenetic relationship is closer to non-classical MHC class I, it can be speculated that the Caja-G might have taken over the immunological function of a classical MHC class I molecule. This is supported by analysis of cotton-top tamarin MHC-G, showing high polymorphism at T-cell receptor, natural killer cell receptor and antigen-binding sites.…”