Genetic analyses of alloreactions between recently wild and classical inbred strains of Syrian hamsters: evidence in favor of a major histocompatibility complex

The major histocompatibility complex of tassel-eared squirrels. I. Genetic diversity associated with Kaibab squirrels

The complexity and polymorphism of sequences related to the class I and class II genes of mammalian major histocompatibility complexes (MHCs) were investigated in the tassel-eared squirrel subspecies Sciurus aberti kaibabensis or Kaibab squirrel. Kaibab squirrels are geographically isolated on the Kaibab plateau north of the Grand Canyon in Arizona. Genomic DNA from 22 individuals was digested with Eco RI and Bam HI, electrophoresed, blotted, and hybridized with a panel of human class I and class II probes. Sequences homologous to DR alpha, DR beta, DQ beta probes were observed. A single, nonpolymorphic DR alpha-related sequence and multiple, polymorphic DQ alpha-related sequences were observed. Hybridization with DR beta and DQ beta probes revealed multiple, polymorphic sequences with such specificity that no bands were observed to hybridize with both probes. The level of polymorphism of beta sequences exceeded that observed with alpha sequences. Further, three Eco RI bands apparently included at least parts of both alpha and beta sequences. Hybridization of genomic blots with the HLA-B7 class I probe revealed a number of bands comparable in size range and number to other mammalian species. However, only a minor percentage of bands were observed to segregate. The inheritance of these five families of sequences appeared to be neither concordant nor random in the sample population. Based on prior conclusions in other species, these class I and class II sequences are presumed to map to the Kabib MHC, TLSA. Although DQ alpha- and DQ beta-related sequences were concordantly inherited, segregating sequences in the other families could not be assigned to identifiable, segregating haplotypes. These observations suggest that the present-day TSLA haplotypes have been derived from a limited number of progenitor haplotypes through repeated, intra-TSLA recombination.

Syrian hamster DNA shows limited polymorphism at class I-like loci

The class I gene products of the Syrian hamster major histocompatibility complex are unique in that they lack functionally detectable polymorphism. Mouse cDNA and hamster genomic probes were used to analyze the hamster class I gene family using genomic Southern hybridization. These studies revealed that the hamster possesses a complex class I multigene family and that it shares extensive sequence homology with the corresponding mouse sequences. Unlike the mouse, however, the Syrian hamster demonstrates only limited restriction endonuclease polymorphism in these genes. These results suggest that the lack of detectable polymorphism in this species is directly related to limited DNA polymorphism. The data presented here support the hypothesis that this species has undergone an evolutionary bottleneck, i.e., that all surviving members of the species arose from a limited number of progenitors.

Syrian hamsters express two monomorphic class I major histocompatibility complex molecules

The description of the Syrian hamster major histocompatibility complex (MHC), Hm-1, has progressed to the point that multiple class II alloantigens have been defined using structural and functional studies. However, no comparable success has been achieved using allotypic differences to detect class I molecules. We now report that xenoantisera raised in other species against hamster tissues have made it possible to describe class I MHC homologues in the hamster. Evidence which confirms that these molecules exist includes (1) on immunoprecipitation of radiolabeled lymphoid cell lysates, heterodimers of approximate molecular weight 47 000 and 12 000 are identified by sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE), the latter representing hamster beta 2-microglobulin; (2) by direct immunoprecipitation these molecules are ubiquitously expressed on hamster tissues; (3) partial N-terminal amino acid sequence analysis reveals striking homology with class I molecules described in other species. In addition, the amino acid sequence data reveal that two class I molecules are expressed on the surfaces of hamster cells. On two-dimensional PAGE analysis, these molecules are invariant among the several strains of genetically disparate hamsters available for study. We conclude that (1) hamsters have the capacity to make class I MHC molecules, (2) at least two genetic loci are dedicated to this purpose, and (3) no allelic forms can be detected, suggesting that there is no class I polymorphism.

Detection of two distinct class II alpha:beta:Ii complexes in the Syrian hamster

Hamsters alloantisera and a monoclonal antibody originally generated against antigens controlled by the murine I-Ek subregion, which cross-reacts with hamster cell surface antigens, have been used to define two distinct Ia-like complexes in the Syrian hamster. These complexes have been named alpha 1:beta 1 and alpha 2:beta 2 and are detected by hamster alloantisera or monoclonal antibody 14-4-4, respectively. For the three strains studied, alpha 1:beta 1 appears to be polymorphic in both alpha and beta chains, while the alpha 2:beta 2 complex is nonpolymorphic, as revealed by 2-D PAGE analyses. A third nonpolymorphic glycoprotein that appears to be the hamster's equivalent of the murine invariant chain (Ii) is associated with both the alpha 1:beta 1 and alpha 2:beta 2 complexes. In addition, we report the first biochemical detection of polymorphism between the closely related CB and MHA Syrian hamster strains.