[Diversity of the HLA-DQ gene]

Genomic DNA obtained from B lymphoblastoid cell line was digested with appropriate restriction endonuclease and hybridized with several probes specific for HLA-DQ gene. DNA probe which detects intron between DQ beta 1 and beta 2 domains suggested the intron insertion event of Alu-like repetitive sequence in DR7DQw2 haplotype. Southern hybridization with DQA1 3' untranslated (UT) region probe showed DQw2-type hybridization pattern in DR7LDQw3 haplotype. On the contrary, DQB1 3'UT region probe showed DQw3-type pattern in the same haplotype, which strongly supports the previous suggestion that recombination occurs between DQA1 and DQB1 genes in DR7DQw3 haplotype. 3'UT region probes of DQA1 and DQB1 genes failed to detect restriction fragment lenght polymorphism (RFLP) between DR4DQw3 and DR4DQw4 haplotypes. DNA sequencing of DQB1 genomic clone derived from KT3 cell line (DR4DQw4) revealed striking homology of beta 2 domain, 5'UT region, 3'UT region and intervening sequence between beta 1 and beta 2 domains in DR4DQw3 and DR4DQw4 haplotypes. This structural similarity suggests that DQw3 and DQw4 genes are generated from a common ancestral gene.