CYP21 mutations and congenital adrenal hyperplasia

Abstract

Congenital adrenal hyperplasia (CAH) is a common autosomal recessive disorder caused mainly by defects in the steroid 21-hydroxylase (CYP21) gene. More than 90% of CAH cases are caused by mutations of the CYP21 gene on chromosome 6p21.3. The wide range of CAH phenotypes is associated with multiple mutations known to affect 21-hydroxylase enzyme activity. To date, 56 different CYP21 mutations have been reported, mostly point mutations, but small deletions or insertions have been described too, as well as complete gene deletions. Fifteen mutations, constituting 90-95% of alleles, are derived from intergenic recombination of DNA sequences between the CYP21 gene and the highly homologous CYP21P pseudogene, while the remaining are spontaneous mutations. A reliable and accurate detection of CYP21 mutations is not only important for clinical diagnosis, but also for carrier detection as there is a high variability in the basal level of 17-hydroxyprogesterone between normal and heterozygous individuals. Several strategies based on polymerase chain reaction (PCR)-driven amplification with allele-specific oligonucleotides to the CYP21 gene have been developed. It has been demonstrated that one reaction for PCR amplification of the CYP21 gene and the chimeric CYP21P/CYP21 gene using mixed primers in combination with nested PCR and single-strand conformation polymorphism is considered highly efficient and accurate for molecular diagnosis of CAH due to 21-hydroxylase deficiency.

CYP21 gene mutations in Brazilian patients with 21-hydroxylase deficiency from the Amazon region

“…The gene encoding human 21-OH (CYP21) is located at 6p21.3, within HLA class III, approximately 30 kb apart from its pseudogene (CYP21P), which is inactive due to the presence of several inactivating mutations (White et al, 1985;Higashi et al, 1986;Lee, 2001). CYP21 and CYP21P, both with 10 exons, share about 98% homology in their exons and about 96% in their introns.…”

The chimeric CYP21P/CYP21 gene and 21-hydroxylase deficiency

“…To date, 72 different CYP21 mutations have been reported (Human Gene Mutation Database 2003), among which 57 are spontaneous mutations. The remaining 15 mutations (Lee 2001) are believed to be products of intergenic recombinations of DNA sequences between the CYP21 gene and the highly homologous CYP21P pseudogene. These mutations can be identified by allele-specific oligonucleotide (ASO) (Speiser et al 1994) and reverse dot-blot hybridizations (Yang et al 2001), direct DNA sequencing (Tajima et al 1993), PCR/ligase (Day et al 1995), and the amplification-created restriction site (ACRS) method (Lee et al 1996).…”

Structural analysis of the chimeric CYP21P/CYP21 gene in steroid 21-hydroxylase deficiency

“…Fragments of 3.5 kb (Lee et al 2000a;Lee 2001) covering the sequences of the CYP21 genes from Ϫ313 to 3170 (Higashi et al 1986) were generated. The PCR products were further subcloned to the pGEM-T vector system (Promega, Madison, WI, USA).…”