Asp 57 and Arg 52 of the HLA DQ as genetic markers for insulin-dependent diabetes mellitus in Saudis

ABSTRACT

To investigate the significance of Asp 57 and Arg 52 in HLA DQB-and A chains in the development of insulin-dependent diabetes mellitus [IDDM]. This study was incorporated in a national study of the epidemiology of diabetes mellitus in the Saudi Arab population where analysis for Asp 57 and Arg 52 of the HLA DQ was conducted on samples from patients suffering from IDDM. Subjects studied were 38 patients diagnosed as IDDM using the criteria published by the world health organization and 37 health non-diabetic individuals, selected as controls. The DNA was extracted from the buffy coat and subjected to polymerase chain reaction to amplify the DNA region encoding the HLA DQB-and A-chains. Dot blot analysis of the amplified material was carried out using allele apecific oligonucleotide probes to identify the presence of Asp or non-Asp codons at position 57 and Arg and non-Arg codons at position 52 of the HLA DQB and A respectively. The results demonstrated a significantly higher gene frequency of non-Asp at position 57 [60.5%] and of Arg 52 [46.1%] in the IDDM patients compared with the normal group. On the other hand the gene frequency of Asp 57 and non-Arg 52 were higher in the normal non-diabetic individuals compared with the IDDM group though both non-Asp 57 [43.2%] and Arg 52 [23.0%] were found in the normal non-diabetic controls. These results suggest that the absence of aspartic acid at position 57 of the HLA DQB-chain [i.e. non-Asp 57] and the presence of arginine in position 52 of the HLA DQA-chain [i.e. Arg 52] can be useful, but not confirmatory markers, for susceptibility to IDDM