SFEBES2008 Poster Presentations Steroids (35 abstracts)
Functional and structural characterisation of three CYP21A2 mutations associated with simple virilising and non classic congenital adrenal hyperplasia
Vivek Dhir 1 , Caroline Bleicken 1 , Lourdes Loidi 2 , Silvia Parajes 2 , Celse Quinteiro 2 , Fernando Dominguez 2 , Joachim Grötzinger 4 , Wolfgang Sippell 3 , Felix Riepe 3 , Wiebke Arlt 1 & Nils Krone 1
1University of Birmingham, Birmingham, UK; 2Unidad de Medicina Molecular, Santiago, Spain; 3University Hospital Schleswig-Holstein, Kiel, Germany; 4Christian-Albrechts Universität zu Kiel, Kiel, Germany.
Congenital adrenal hyperplasia (CAH) due to steroid 21-hydroxylase (CYP21A2) deficiency is the commonest inborn error in steroid hormone biosynthesis and the most frequent cause of congenital adrenal hyperplasia. The classic forms of 21-hydroxylase deficiency, salt-wasting (SW) and simple virilising (SV), usually present in the neonatal period with some simple virilising patients presenting later in childhood with precocious pseudopuberty. The non-classic form (NCCAH) mostly manifests in adolescence or early adulthood with hirsutism, oligomenorrhea and anovulation in women and oligo-/azoospermia in men. CYP21A2 catalyses key steps in glucocorticoid biosynthesis and an excellent genotype–phenotype correlation based on in vitro enzyme activity assays has been demonstrated. Hence the severity and type of disease can be predicted once a mutation has been characterised in vitro. Here, we have identified and functionally characterised three CYP21A2 mutations A265V, W302S and D322G in 6 patients with clinical suspicion of NCCAH (A265V, D322G) and 1 patient with suspected SV-CAH (W302S). Analyzing each mutation in vitro using two separate systems (COS7 cell assay and yeast microsomal expression assay) revealed that A265V had an enzyme activity similar to wild-type (~90%), and hence is a polymorphism. W302S was found to have minimal residual activity compatible with simple virilising CAH (~3–4%) whereas 21-hydroxylase activity observed for D322G fitted into the range usually observed for mutations associated with NCCAH (25–40%). Both assay systems reliably produced comparable results. The observed in vitro effects correlated with the mutation effects predicted from mutation modeling in our 3D computational CYP21A2 model. These results indicate the importance of genotyping in patients with suspected NCCAH. Furthermore, they nicely illustrate that functional and structural characterization of CYP21A2 mutations helps to differentiate sequence variants from functionally relevant mutations and reliably predicts disease severity in patients affected by 21-hydroxylase deficiency.
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Endocrine Abstracts
ISSN 1470-3947 (print) | ISSN 1479-6848 (online)
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