STRUCTURE-BASED PREDICTION OF CYP21A2 NOVEL VARIANTS: A SURVEY OF GENE VARIATIONS

BRUQUE C.D., DELEA M., SIMONETTI L., ORZA J.V., BUZZALINO N., ESPECHE L.D., BENAVIDES B, NADRA A.D., DAIN L., FERNÁNDEZ C.S

Congreso; LXI REUNIÓN ANUAL DE LA SOCIEDAD ARGENTINA DE INVESTIGACIÓN CLÍNICA; 2016

P { margin-bottom: 0.08in; }Ina previous work we have developed and validated a procedure with thegoal of predicting the effect of newly uncharacterized mutationsvariants in the CYP21A2 gene with improved accuracy based on the highidentity bovine and human templates. In this work we performed anexhaustive survey of mutations and SNPs (found in general population)in the coding sequence of the CYP21A2 gene encoding the21-hydroxylase enzyme. All reported variants were initiallyclassified according to their putative impairment on proteindysfunction and/or location in the structure. We focused our analyseson that affecting protein stability lacking functional assays aimingto predict their residual enzymatic activity (REA). Variants wereretrieved from the Human Cytochrome P450 Allele Nomenclaturedatabase, dbSNPs, 1000 Genome Database and from the bibliography. Thepredicted free energy of each of the mutants relative to the wildtype counterpart (ΔΔG) was calculated by the FoldX algorithm andthe REA was estimated as previously described. When available,phenotype of patients and presence of a mutation in the homologousallele were also considered. A total of 343 variants were collected,148 were presumed to be involved in protein stability and 108 lackedfunctional assays. For the latest group, in 10/32 mutants the REA wasin accordance with the expected one, while in 9 no information wasavailable to perform such correlation. In 52/76 SNPs the predictedREA was above of 75% and these SNPs were considered asnon-pathogenic. Our tool allowed us to predict the effect ofuncharacterized variants. While most of the SNPs showed no biologicalimplications, some of them may have a deleterious effect. Since theclinical manifestation of the 21-hydroxylase deficiency depends onthe less affected allele, the estimation of the residual activity ofa novel variant is important for an accurate genetic counseling