Context: CYP21A2 deficiency represents 95% of congenital adrenal hyperplasia cases (CAH), a group of genetic disorders that affect steroid biosynthesis. The genetic and functional analysis provides critical tools to elucidate complex CAH cases. One of the most accessible tools to infer the pathogenicity of new variants is in silico prediction. Objective: Analyze the performance of in silico prediction tools to categorize missense single nucleotide variants (SNVs) of the CYP21A2. Methods: SNVs of the CYP21A2 characterized in vitro by functional assays were selected to assess the performance of online single and meta predictors. SNVs were tested separately or in combination with the related phenotype (severe or mild CAH form). In total, 103 SNVs of the CYP21A2 (90 pathogenic and 13 neutral) were used to test the performance of 13 single-predictors and four meta-predictors. Results: SNVs associated with the severe phenotypes were well categorized by all tools, with an accuracy between 0.69 (PredictSNP2) and 0.97 (CADD), and Matthews' correlation coefficient (MCC) between 0.49 (PoredicSNP2) and 0.90 (CADD). However, SNVs related to the mild phenotype had more variation, with the accuracy between 0.47 (S3Ds&GO and MAPP) and 0.88 (CADD), and MCC between 0.18 (MAPP) and 0.71 (CADD). Conclusion: From our analysis, we identified four predictors of CYP21A2 pathogenicity with good performance. These results can be used for future analysis to infer the impact of uncharacterized SNVs' in CYP21A2.

Deficiency of Cytochrome P450 Steroid 21-hydroxylase (CYP21A2) represents 90% of cases in congenital adrenal hyperplasia (CAH), an autosomal recessive disease caused by defects in cortisol biosynthesis. Computational prediction along with functional studies are often the only way to classify variants to understand the links to disease-causing effects. Here we investigated the pathogenicity of uncharacterized variants in the CYP21A2 gene reported in the Brazilian and Portuguese populations. Physicochemical alterations, residue conservation, and effect on protein structure were accessed by computational analysis. The enzymatic performance was obtained by functional assay with the wild-type and mutant CYP21A2 proteins expressed in HEK293 cells. Computational analysis showed that p.W202R, p.E352V, and p.R484L have severely impaired the protein structure, while p.P35L, p.L199P, and p.P433L have moderate effects. The p.W202R, p.E352V, p.P433L, and p.R484L variants showed residual 21OH activity consistent with the simple virilizing phenotype. The p.P35L and p.L199P variants showed partial 21OH efficiency associated with the non-classical phenotype. Additionally, p.W202R, p.E352V and p.R484L also modified the protein expression level. We have determined how the selected CYP21A2 gene mutations affect the 21OH activity through structural and activity alteration contributing to the future diagnosis and management of 21OH deficiency.

Context: Mutations in Cytochrome P450 oxidoreductase (POR) cause a form of congenital adrenal hyperplasia (CAH). We are reporting a novel R550W mutation in POR identified in a 46, XX patient with signs of aromatase deficiency. Objective: Analysis of aromatase deficiency from R550W mutation in POR. Design, Setting, and Patient: Both the child and the mother had signs of virilization. Ultrasound revealed the presence of uterus and ovaries. No defects in CYP19A1 were found, but further analysis with a targeted Disorders of Sexual Development NGS panel (DSDSeq.V1, 111 genes) on a NextSeq (Illumina) platform in Madrid and Barcelona, Spain, revealed compound heterozygous mutations c.73_74delCT/p.L25FfsTer93 and c.1648C>T/p.R550W in POR. WT and R550W POR were produced as recombinant proteins and tested with multiple cytochrome P450 enzymes at University Children’s Hospital, Bern, Switzerland. Main Outcome Measure and Results: R550W POR showed 41% of the WT activity in cytochrome c and 7.7% activity for reduction of MTT. Assays of CYP19A1 showed a severe loss of activity and CYP17A1, as well as CYP21A2 activities, were also lost by more than 95%. Loss of CYP2C9, CYP2C19, and CYP3A4 activities was observed for the R550W-POR. Predicted adverse effect on aromatase activity as well as a reduction in binding of NADPH was confirmed. Conclusions: Pathological effects due to POR R550W were identified, expanding the knowledge of molecular pathways associated with aromatase deficiency. Screening of the POR gene may provide a diagnosis in CAH without defects in genes for steroid metabolizing enzymes.