title: Molecular cloning of a polymorphic DNA endonuclease fragment associates insulin-dependent diabetes mellitus with HLA-DQ.
abstract: A BamHI 3.7-kilobase (kb) fragment detected by an HLA-DQ beta-chain complementary DNA (cDNA) probe and negatively associated with insulin-dependent diabetes mellitus (IDDM) was cloned and sequenced to localize the polymorphism to BamHI sites in intervening sequences of an HLA-DQ beta-chain gene. A probe of the first intervening sequence (IVS 1) showed the BamHI 3.7-kb fragment in 6 of 17 HLA-DR3/4 controls but in 0 of 13 DR-identical IDDM patients. All IDDM patients (13 of 13) had BamHI fragments of 12 and 4 kb, detected in 9 of 17 controls (P less than 0.02). The simple restriction fragment length polymorphism pattern of the IVS 1 probe was exploited by comparing 113 IDDM patients with 177 healthy controls to show increased prevalences in IDDM of the 12-kb (P less than 0.0001) and 4-kb (P less than 0.0001) fragments. In IDDM patients younger than 20 yr at onset, 98% were 12- and/or 4-kb positive, compared with 63% of controls (P less than 0.0001), giving a relative risk of 91.8 for individuals with both fragments. The 12-kb fragment was linked to HLA-DR4, and the 4-kb fragment to HLA-DR3. Both serologic markers were split and a non-DR3/non-DR4 IDDM patient was 4-kb positive. HLA-DQ seems therefore closer, than HLA-DR, to an IDDM susceptibility gene.
mesh_terms: D000595:Amino Acid Sequence; D001483:Base Sequence; D003001:Cloning, Molecular; D004247:DNA / Q000032:analysis; D004262:DNA Restriction Enzymes / Q000378:metabolism; D015245:Deoxyribonuclease BamHI; D003850:Deoxyribonuclease I / Q000378:metabolism*; D003922:Diabetes Mellitus, Type 1 / Q000235:genetics* / Q000276:immunology; D003924:Diabetes Mellitus, Type 2 / Q000235:genetics / Q000276:immunology; D006681:HLA-D Antigens / Q000235:genetics*; D006683:HLA-DQ Antigens / Q000235:genetics*; D006684:HLA-DR Antigens / Q000235:genetics; D006801:Humans; D009693:Nucleic Acid Hybridization; D011110:Polymorphism, Genetic; D012150:Polymorphism, Restriction Fragment Length
chemical_list: D006681:HLA-D Antigens; D006683:HLA-DQ Antigens; D006684:HLA-DR Antigens; D004247:DNA; D004262:DNA Restriction Enzymes; D015245:Deoxyribonuclease BamHI; D003850:Deoxyribonuclease I