Analysis of CYP21A2 gene mutation and phenotype in patients with 21-hydroxylase deficiency

Abstract

Objective To investigate the spectrum of CYP21A2 gene mutation and the correlation between genotype and phenotype in patients with 21-hydroxylase deficiency in Tianjin and surrounding areas. Methods Genomic DNA was extracted from the peripheral blood samples of the proband. Locus-specific PCR, direct sequencing of PCR amplification products, and multiplex ligation-dependent probe amplification were applied to detect pathogenic gene CYP21A2 and the relationship between genotypes and phenotypes was analyzed. Results (1) Of 35 patients with 21-hydroxylase deficiency, 25 were classified as salt-wasting phenotype and 10 were simple virilizing phenotype. (2) 69 mutant alleles were detected in a total of 70 alleles in 35 patients. Only one mutant allele was detected in one patient. Two mutant alleles were detected in all other patients, with the mutation detection rate 98.6%. (3) A total of 6 types of mutations were detected, of which c. 293-13C /A>G (I2G) was the most common, accounting for 57.1% (40/70), followed by 18.6% (13/70) for large gene deletion or conversion, and 14.3% (10/70) for p. I173N. In addition, a novel mutation, c. 949C>T (p.R317X), which has not been reported previously, was detected as a pathogenic mutation. (4) Correlation analysis of genotype and phenotype in 35 children showed that the phenotype predicted by genotype was consistent with the actual salt-wasting phenotype in 31 children, and those in three children were inconsistent with the actual clinical phenotype. Conclusion The mutation characteristics of CYP21A2 gene in patients with 21-hydroxylase deficiency in Tianjin and surrounding areas are slightly different from those reported in other regions in China. A mutation c. 949C>T has not been reported, which enriches the mutation spectrum of CYP21A2 gene and provide the foundation for genetic counseling and prenatal diagnosis. Key words: 21-Hydroxylase deficiency; CYP21A2 gene; Mutation