Mutational spectrum of the steroid 21-hydroxylase gene in Austria: Identification of a novel missense mutation

This study attempted an analysis of the mutational spectrum of 21-hydroxyla se deficiency in 79 unrelated Austrian patients with classical and nonclass ical forms of congenital adrenal hyperplasia and their respective 112 famil y members. Apparent large gene deletions/conversions were present in 31% of the 158 unrelated congenital adrenal hyperplasia alleles, whereas the most frequent point mutations were intron 2 splice (22.8%),I172N (15.8%), V281L (12%), and P30L (7.6%), in line with the frequencies reported for other co untries. In 5 of the 12 congenital adrenal hyperplasia alleles carrying a P 30L mutation the aberration is based on a single base substitution, whereas the remaining 7 represent part of a CYP21B conversion (I allele) or CYP21B /21A hybrid gene (6 alleles), the latter characterized by a junction site b efore intron 2 as indicated by Southern blot, PCR, and sequence analyses. Previously described mutations were not present in 1.2% of unrelated congen ital adrenal hyperplasia alleles, including one female patient presenting w ith severe genital virilization. Sequence analysis of the complete function al 21-hydroxylase gene revealed an as yet undescribed mutation in exon 10-A rg(426)His, which has not yet been described to represent a common pseudoge ne sequence. In vitro expression experiments showed the Arg(426)His Mutant to exhibit only low enzyme activity toward the natural substrate 17-hydroxy progesterone corresponding to the degree of disease manifestation in the pa tient in whom it was found.