Molecular genetic and biochemical analysis of woodchuck (Marmota monax) MHC class I polymorphism.

The woodchuck (Marmota monax) is an animal model that is used in the study of human hepatitis B virus ( HBV ) infection. A knowledge of woodchuck MHC class I (Mamo-I) genes and gene products is therefore essential for understanding the antigen-specific T-cell responses in this animal model. A number of Mamo-I genes have been identified by molecular cloning and sequencing. However, the allelic nature of these genes has not been proven by classical genetics like the segregation analysis in families. In this study, we analyzed the allelic diversity of Mamo-I in two three-generation woodchuck families including 15 members by sequencing of Mamo-I genes and immunoblotting of Mamo-I proteins after one-dimensional isoelectric focusing (1D-IEF). In addition to four published Mamo-I alleles, six new alleles that belonged to the same locus as the known Mamo-I alleles (Mamo-A) were found within the two woodchuck families. A typical Mendelian segregation of Mamo-I gene and antigens was observed in the families studied. For simple and rapid detection of allelic variability of Mamo-I gene, a typing method based on the detection of PCR products amplified by sequence specific primers (SSP) has been developed and tested in 41 unrelated animals. The most prevalent allele was Mamo-A01 with a frequency of 21.9% followed by Mamo-A07 (12.2%). Our study established Mamo-A as a classical MHC class I locus by the polymorphic and allelic nature of Mamo-I gene in the woodchuck.