| 1. |
- Karlsson, Leif, et al.
(author)
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Novel non-classic CYP21A2 variants, including combined alleles, identified in patients with congenital adrenal hyperplasia
- 2019
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In: Clinical Biochemistry. - : Elsevier BV. - 0009-9120 .- 1873-2933. ; 73, s. 50-56
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Journal article (peer-reviewed)abstract
- Objective: Congenital adrenal hyperplasia (CAH) is an inborn error of metabolism and a common disorder of sex development where >90% of all cases are due to 21-hydroxylase deficiency. Novel and rare pathogenic variants account for 5% of all clinical cases. Here, we sought to investigate the functional and structural effects of four novel (p.Val358Ile, p.Arg369Gln, p.Asp377Tyr, and p.Leu461Pro) and three combinations of CYP21A2 variants (i.e. one allele containing two variants p.[Ile172Asn;Val358Ile], p.[Val281Leu;Arg369Gln], or p.[Asp377Tyr;Leu461Pro]) identified in patients with CAH.Methods: All variants were reconstructed by in vitro site-directed mutagenesis, the proteins were transiently expressed in COS-1 cells and enzyme activities directed toward the two natural substrates (17-hydroxyprogesterone and progesterone) were determined. In parallel, in silico prediction of the pathogenicity of the variants based on the human CYP21 X-ray structure was performed.Results: The novel variants, p.Val358Ile, p.Arg369Gln, p.Asp377Tyr, and p.Leu461Pro exhibited residual enzymatic activities within the range of non-classic (NC) CAH variants (40–82%). An additive effect on the reduction of enzymatic activity (1–17%) was observed when two variants were expressed together, as identified in several patients, resulting in either NC or more severe phenotypes. In silico predictions were in line with the in vitro data except for p.Leu461Pro.Conclusions: Altogether, the combination of clinical data, in silico prediction, and data from in vitro studies are important for establishing a correct genotype and phenotype correlation in patients with CAH.
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| 2. |
- Michelatto, Debora de Paula, et al.
(author)
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Functional and Structural Consequences of Nine CYP21A2 Mutations Ranging from Very Mild to Severe Effects
- 2016
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In: International Journal of Endocrinology. - : Hindawi Limited. - 1687-8337 .- 1687-8345.
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Journal article (peer-reviewed)abstract
- We present the functional and structural effects of seven novel (p.Leu12Met, p.Arg16Cys, p.Ser101Asn, p.Ser202Gly, p.Pro267Leu, p.Gln389 Ala391del, and p.Thr450Met) and two previously reported but not studied (p.Ser113Phe and p.Thr450Pro) CYP21A2 mutations. Functional analyses were complemented with in silico prediction of mutation pathogenicity based on the recently crystallized human CYP21A2 structure. Mutated proteins were transiently expressed in COS-1 cells and enzyme activities towards 17-hydroxyprogesterone and progesterone were determined. Residual enzyme activities between 43% and 97% were obtained for p.Arg16Cys, p.Ser101Asn, p.Ser202Gly, p.Pro267Leu, and p.Thr450Met, similar to the activities of the well-known nonclassic mutations p.Pro453Ser and p.Pro482Ser, whereas the p.Leu12Met variant showed an activity of 100%. Conversely, the novel p.Ser113Phe, p. Gln389 Ala391del, and p.Thr450Promutations drastically reduced the enzyme function below 4%. The K-m values for all novel variants were in the same order of magnitude as for the wild-type protein except for p.The450Met. The maximum velocity was decreased for all mutants except for p.Leu12Met. We conclude that p. Leu12Met is a normal variant; the mutations p.Arg16Cys, p.Ser101Asn, p.Ser202Gly, p.Pro267Leu, and p.Thr450Met could be associated with very mild nonclassic CAH, and the mutations p.Ser113Phe, p.Gln389 Ala391del, and p.Thr450Pro are associated with classic CAH. The obtained residual activities indicated a good genotype-phenotype correlation.
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| 3. |
- Barbaro, Michela, et al.
(author)
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In vitro functional studies of rare CYP21A2 mutations and establishment of an activity gradient for nonclassic mutations improve phenotype predictions in congenital adrenal hyperplasia
- 2015
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In: Clinical Endocrinology. - : Wiley. - 0300-0664 .- 1365-2265. ; 82:1, s. 37-44
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Journal article (peer-reviewed)abstract
- BackgroundA detailed genotype-phenotype evaluation is presented by studying the enzyme activities of five rare amino acid substitutions (Arg233Gly, Ala265Ser, Arg341Trp, Arg366Cys and Met473Ile) identified in the CYP21A2 gene in patients investigated for Congenital adrenal hyperplasia (CAH). ObjectiveTo investigate whether the mutations identified in the CYP21A2 gene are disease causing and to establish a gradient for the degree of enzyme impairment to improve prediction of patient phenotype. Design and patientsThe CYP21A2 genes of seven patients investigated for CAH were sequenced and five mutations were identified. The mutant proteins were expressed in vitro in COS-1 cells, and the enzyme activities towards the two natural substrates were determined to verify the disease-causing state of the mutations. The in vitro activities of these rare mutations were also compared with the activities of four mutations known to cause nonclassic CAH (Pro30Leu, Val281Leu, Pro453Ser and Pro482Ser) in addition to an in silico structural evaluation of the novel mutants. Main outcome measureTo verify the disease-causing state of novel mutations. ResultsFive CYP21A2 mutations were identified (Arg233Gly, Ala265Ser, Arg341Trp, Arg366Cys and Met473Ile). All mutant proteins exhibited enzyme activities above 5%, and four mutations were classified as nonclassic and one as a normal variant. By comparing the investigated protein changes with four common mutations causing nonclassic CAH, a gradient for the degree of enzyme impairment could be established. Studying rare mutations in CAH increases our knowledge regarding the molecular mechanisms that render a mutation pathogenic. It also improves phenotype predictions and genetic counselling for future generations.
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