Preferential transmission of maternal allele with DQA1*0301-DQB1*0302 haplotype to affected offspring in families with type 1 diabetes

To approach the possible involvement of an epigenetic mechanism in the pathogenesis of type 1 diabetes, we investigate here a parent-of-origin effect in transmission of the susceptible alleles at HLA-DQ loci by the trans-mission disequilibrium test. When we examined alleles of affected offspring of Japanese origin in 28 nuclear families, the maternal alleles were significantly different from the paternal alleles. Furthermore, the maternal alleles with the susceptible DQA1^*0301-DQB1^*0302 haplotype showed strong transmission disequilibrium with antiglutamic acid decarboxylase antibody-positive type 1 diabetes, while the paternal alleles with the same haplotype did not. This differential transmission disequilibrium of the susceptible allele was confirmed by the contingency table analysis for transmitted or nontransmitted alleles of both parental origin. The unique transmission of the susceptible allele observed supports the hypothesis that an epigenetic mechanism including genomic imprinting at the HLA-DQ region is involved in the pathogenesis and the genetic complexity of type 1 diabetes. Received: April 5, 1999 / Accepted: May 29, 1999