Establishment of an assay for detection of gene mutation in congenital adrenal hyperplasia

Abstract

Objective To establish a method of gene mutation detection for congenital adrenal hyperplasia (CAH) by using sequencing, single nucleotide polymorphisms (SNP) analysis and T-A cloning. Methods The blood samples of 33 patients with 21-hydroxylase deficiency (21-OHD) , 2 patients with 17α-hydroxylase deficiency (17-OHD) , the parents of all the patients and 105 healthy children were collected. Genomic DNA were extracted form the blood samples. To detect the gene mutation of CYP21A2,highly specific primers for CYP21A2 gene were designed according to the sequence differences between CYP21A2 gene and its pseudogene. The whole CYP21A2 gene was amplified and sequenced. SNP analysis and TA cloning of PCR products were also carried out. The molecular diagnosis of 17-OHD was based on the amplification and sequencing of CYP17A1 gene. Results The corresponding gene mutations was determined in all the patients based on the method established in this study. Thirteen mutations of CYP21A2 gene were identified in 33 patients with 21-OHD. The 3 most frequent mutation of CYP21A2 gene were IVS2-13A/C >G, p. I172N and chimeric mutation, which accounted for 32% (21/66) ,27% (18/66) and 15% (10/66) respectively. Ninety-one persent mutations of CYP21A2 gene resulted from pseudogene conversion. In 2 patients with 17-OHD, homozygous mutations of CYP17A1 gene, IVS4-6A > G and p. 487_489del were identified separately. All the gene mutations detected in the patients were inherited from their parents. No mutation of CYP21A2 gene or CYP17A1 gene was found in the healthy children. Conclusion A method of gene mutation detection for CAH has been established. It will be beneficial to clinical diagnosis of CAH. Key words: Adrenal hyperplasia, congenital; Steroid 21-hydroxylase; Steroid 17-alpha-hydroxylase; Mutation