Effect of a novel mutation in 5'-regulatory region of aldose reductase gene on its expression.

To study the genetic variation in 5'-regulatory region of aldose reductase (AR) gene that might influence expression and the relationship between variations and diabetic complication (DC), PCR-single stranded conformational polymorphism (SSCP) was used to screen the 5'-regulatory region of AR gene in Chinese patients with type 2 diabetes mellitus. A novel mutation, C(-167) --> A substitution which created a new CCAAT box was found only in two diabetic patients. These two patients have no retinopathy, and the AR activity of their erythrocytes was within low range in patients without DC. The DNA segments of AR wild type and mutant were subcloned into pCAT reporter vector, and CAT assays were performed to assess promoter activity. The interaction between the DNA segments and nuclear proteins was determined by using competitive gel electrophoretic mobility shift assay (EMSA). The transcriptional activity of mutant (5.7% +/-2.9%) was lower than that of wild type (15.7% +/- 4.1%) (P<0.01), and the mobility shift of mutant was also slower than that of wild type. The results indicated the mutation C(-167) -->A in AR gene might prevent or delay the development of DC by repressing the expression of AR gene.