High variability in CYP21A2 mutated alleles in Spanish 21-hydroxylase deficiency patients, six novel mutations and a founder effect.
OBJECTIVE
To detect common as well as rare and novel CYP21A mutations in 21-hydroxylase deficiency patients. To estimate the distribution of mutations and compare them with other European studies. To construct haplotypes linked to a recurrent novel mutation.


METHODS
Genetic analysis by sequencing the entire CYP21A2 gene plus Southern blot.


METHODS
A total of 138 unrelated Spanish patients: 122 nonclassical forms (NCF) and 16 classical forms (CF) were studied.


RESULTS
Among the 266 nonrelated mutated alleles; CYP21A2 deletions/conversions and a spectrum of 27 different mutated alleles were found: 15 different single point mutations, 8 nucleotide deletions in exon 3, 3 mutation clusters in exon 6, 9 alleles with more than one mutation, one 21-nucleotide duplication in exon 10, and one allele with CYP21A2 duplicated and both copies mutated. The most frequent mutation in NCF alleles is V281L (71.8%). Among CFs, the most common is I2 g (20%) and Q318X (16%) and rare alleles (21.9%). Six novel causative mutations were found, four associated with CF: I46+1nt, R444X, P463L and M473_R479dup and two associated with NCF: W302 and D322G. The R444X mutation was found in seven unrelated patients and it appeared only once in an ancestral haplotype. In addition, we found a novel single nucleotide polymorphism with a 31.5% frequency for the rare allele.


CONCLUSIONS
A great diversity of haplotypes with a large spectrum of mutated alleles was found. The frequency of the V281L mutation was the highest reported and the relatively high frequency of R444X was the result of a founder effect.
Loidi
Lourdes
L
Fundación Pública Gallega de Medicina Genómica, Unidad de Medicina Molecular, Complejo Hospitalario Universitario de Santiago de Compostela, Santiago de Compostela, Spain. lloidi@usc.es
Quinteiro
Celsa
C
Parajes
Silvia
S
Barreiro
Jesús
J
Lestón
Domingo G
DG
Cabezas-Agrícola
José M
JM
Sueiro
Aurelio M
AM
Araujo-Vilar
David
D
Catro-Feijóo
Lidia
L
Costas
Javier
J
Pombo
Manuel
M
Domínguez
Fernando
F
D000312:Adrenal Hyperplasia, Congenital / Q000201:enzymology / Q000235:genetics*; D000483:Alleles; D001483:Base Sequence; D005192:Family Health; D005260:Female; D005785:Gene Conversion / Q000235:genetics; D017353:Gene Deletion; D020440:Gene Duplication; D005787:Gene Frequency / Q000235:genetics; D006239:Haplotypes / Q000235:genetics; D006801:Humans; D008297:Male; D009154:Mutation / Q000235:genetics*; D010641:Phenotype; D017354:Point Mutation / Q000235:genetics; D020641:Polymorphism, Single Nucleotide / Q000235:genetics; D013255:Steroid 21-Hydroxylase / Q000235:genetics*
D013255:Steroid 21-Hydroxylase