Mutation Analysis in Patients with Congenital Adrenal Hyperplasia in the Spanish Population: Identification of Putative Novel Steroid 21-Hydroxylase Deficiency Alleles Associated with the Classic Form of the Disease

Abstract

Steroid 21-hydroxylase deficiency, due to the genetic impairment of the CYP21 gene, is a major cause of congenital adrenal hyperplasia (CAH). In about 80% of the cases, the defect is related with the transfer of deleterious point mutations from the CYP21P pseudogene to the active CYP21 gene. Sixteen different point mutations have been searched for in 60 Spanish patients with the classic form of CAH and 171 unaffected family members, using selective amplification of the CYP21 gene followed by allele-specific oligonucleotide hybridization (PCR-ASOH) and sequencing analysis. While 31.9% of the disease alleles carry CYP21 deletions or large gene conversions, around 58% of the alleles carry single point mutations. Corresponding segregation of mutations was found in every case indicating that none of them has apparently appeared de novo. The most frequent mutations found in our sample are i2G, V281L, R356W, Q318X, P453S and F306+t, with rates of 30, 14.2, 10, 9.2, 9.2 and 7.5%, respectively. We found similar frequencies for the A and C polymorphism at position 656 (40 and 31.5%, respectively) in wild-type alleles for the i2G mutation. Around 10% of the alleles, for which no mutations were identified by searching for the sixteen previously known mutations, are currently being sequenced and new possible mutations and polymorphisms have been identified.

<b><i>CYP21A2</i></b> Gene Pathogenic Variants: A Multicenter Study on Genotype–Phenotype Correlation from a Portuguese Pediatric Cohort

“…Alleles with multiple pathogenic variants accounted for 8.2% of unrelated alleles. The percentage of alleles carrying 2 or more pathogenic variants in cis is very variable in previous publications (6.5% in Serbia [38] to 21.6% in Spain [42]). This is related to the methodology used for the diagnosis and the segregation studies, which are extremely important for genetic counseling.…”

CYP21 and CYP21P variability in steroid 21-hydroxylase deficiency patients and in the general population in the Netherlands

“…They vary among different populations. 8,17,18,22,[26][27][28][29][30][31][32][33][34][35][36][37] However, information on the variability of the CYP21P pseudogene, especially in association with the TaqI/BglII haplotypes that define the overall structure of the region, is rather limited. 18,38 Such information is highly relevant to the hypotheses describing the origin of the different categories of disease-causing mutations in CYP21: the location of crossover sites and the extent of conversion zones depend on the composition of the CYP21P gene involved.…”

CYP21 mutations in Brazilian patients with 21-hydroxylase deficiency

“…Other uses of genetic analysis include genetic counseling and ascertainment of which premature infants with elevated screening 17-hydroxyprogesterone concentrations require glucocorticoid therapy (Witchel et al 1997a). Although over 40 different CYP21 mutations have been identified in patients with 21-hydroxylase deficiency Globerman et al 1988;Higashi et al 1988;Speiser et al 1988;White et al 1988;Chiou et al 1990;Helmberg et al 1992;Wedell et al 1992;Wedell and Luthman 1993a;Barbat et al 1995;Lajic and Wedell 1996;Lajic et al 1997;Levo and Partanen 1997;Krone et al 1998;Lee et al 1998;Witchel et al 1998;Lobato et al 1999;Ohlsson et al 1999;http:www.uwcm.ac.uk/uwcm/mg/search/120605.html), only nine of these mutations account for the majority of affected alleles (Wedell 1998).…”