Allele-specific methylation in the 5'-regulatory region of class II DQ beta genes in the human major histocompatibility complex (MHC): relationship to autoimmune disease susceptibility.

The DNA methylation state of the 5'-regulatory region of human HLA-DQ beta genes was examined. Two restriction enzymes were utilized to detect methylated (meCG) dinucleotides in the 5'-regulatory region of the DQ-beta genes: the restriction enzyme Msp I, which recognizes CCGG and CmeCGG, and Hpa II recognizes only the unmethylated CG sequence. DNA samples were prepared from 95 HLA-typed individuals including 40 B-lymphoblastoid cell lines and peripheral blood leukocytes of 55 individuals. Of these samples, 20 were from parents of individuals with insulin-dependent diabetes. Allele specific methylation was observed in particular DR-associated DQ-beta gene alleles. The DQw8 (DQw3.2) allele, most DQw7 (DQw3.1) alleles, and the DR3-associated DQw2 allele were all unmethylated. The parental methylation state was stably transmitted to offspring. Because these DQ alleles are highly associated with several autoimmune diseases, our results raise the possibility that the regulation of expression of these particular DQ-beta alleles might be different from that of other alleles, and that the 5'-regulatory DNA sequences of these particular DQ beta alleles may be responsible for, or contribute to, susceptibility to autoimmune diseases.