Comments to “A rational, non-radioactive strategy for the molecular diagnosis of congenital adrenal hyperplasia due to 21-hydroxylase deficiency” (original) (raw)
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Gene, 2013
Context: Molecular diagnosis of congenital adrenal hyperplasia (CAH) due to 21-hydroxylase deficiency (21OHD) has not been straightforward. Objective: To conduct a comprehensive genetic analysis by Multiplex Ligation dependent Probe Amplification (MLPA) and evaluate its reliability for the molecular CAH-21OHD diagnosis. Patients and methods: We studied 99 patients from 90 families with salt-wasting (SW; n = 32), simple-virilizing (SV; n = 29), and non-classical (NC; n = 29) CAH-21OHD. Molecular analysis was sequentially performed by detecting the most frequent point mutations by allele-specific oligonucleotide polymerase chain reaction (ASO-PCR), large rearrangements by MLPA, and rare mutations by direct sequencing. Parental segregation was evaluated. Results: ASO-PCR detected microconversions in 164 alleles (91.1%). MLPA identified CYP21A1P large conversions to CYP21A2 in 7 of the remaining 16 (43.7%), 30-kb deletions including the 3′-end of CYP21A1P, C4B, and the 5′-end of CYP21A2 in 3 of the 16 (18.7%), and a complete CYP21A2 deletion in one (6.3%). Five alleles (2.7%) required direct sequencing; three mutations located in the CYP21A2 gene and two derived from CYP21A1P were found. No parental segregation was observed in patients with the c.329_336del and/or the CL6 cluster mutations. These cases were not diagnosed by ASO-PCR, but MLPA detected deletions in the promoter region of the CYP21A2 gene, explaining the genotype/phenotype dissociation. Conclusion: Using the proposed algorithm, all alleles were elucidated. False-positive results in MLPA occurred when mutations or polymorphisms were located close to the probe-binding regions. These difficulties were overcome by the association of MLPA with ASO-PCR and paternal segregation. Using these approaches, we can successfully use MLPA in a cost-effective laboratory routine for the molecular diagnosis of CAH-21OHD.
Human Molecular Genetics, 1996
Steroid 21-hydroxylase deficiency is among the most common inborn errors of metabolism in man. Characterization of mutations in the 21-hydroxylase gene (CYP21) has permitted genetic diagnosis, facilitated by the polymerase chain reaction (PCR). The most common mutation is conversion of an A or C at nt656 to a G in the second intron causing aberrant splicing of mRNA. Homozygosity for nt656G is associated with profoundly deficient adrenal cortisol and aldosterone synthesis, secondary hypersecretion of adrenal androgens, and a severe form of congenital adrenal hyperplasia (CAH) characterized by ambiguous genitalia and/or sodium wasting in newborns. During the course of genetic analysis of CYP21 mutations in CAH families, we and others have noticed a number of relatives genotyped as nt656G homozygotes, yet showing no clinical signs of disease. A number of lines of evidence have led us to propose that the putative asymptomatic nt656G/G individuals are incorrectly typed due to dropout of one haplotype during PCR amplification of CYP21. For prenatal diagnosis, we recommend that microsatellite typing be used as a supplement to CYP21 genotyping in order to resolve ambiguities at nt656.
Molecular genetics and …, 2006
More than 90% of congenital adrenal hyperplasia (CAH) cases are caused by 21-hydroxylase deWciency. In this study, the CYP21 gene was genotyped in 56 Portuguese unrelated patients with clinical symptoms of 21-hydroxylase deWciency, in a total of 112 independent alleles. CYP21A2 mutations were identiWed in 99.1% of the alleles. The most common point mutation was 1688G > T (25.9%). A previously unreported partial gene conversion, extending from exon 1 to 7, was found in 16.1% of the alleles, in most cases associated to the mutation 1688G > T in the other chromosome, and in patients with nonclassical CAH. Other three distinct partial gene conversions were also identiWed, with lower frequencies: one extends from exon 1 to 3 and the others from exons 3 to 7 and 3 to 8. Two novel mutations were identiWed in two salt-wasting patients: a putative splicing mutation, IVS2 + 5G > A, and the transition 2557C > T, that gives rise to the nonsense mutation R445X. Seven point mutations and a partial gene conversion were responsible for 88 of the studied disease causing alleles, and the overall concordance between genotype and phenotype was 92.9%. With this study the molecular basis of CAH was characterized, for the Wrst time, in Portuguese patients, providing useful results for clinicians in terms of prediction of disease severity, genetic and prenatal counseling.
European journal of endocrinology, 2016
Background: Most congenital adrenal hyperplasia (CAH) patients carry CYP21A2 mutations derived from conversion events involving the pseudogene, and the remaining carry new mutations. Objective: To review causal mutations and genotype-phenotype correlation in 480 Brazilian patients. Methods: DNA was extracted from 158 salt-wasters (SWs), 116 simple virilizing (SV), and 206 nonclassical (NC) patients. Fourteen point mutations were screened by allele-specific PCR, large rearrangements by Southern blotting/ MLPA, and sequencing was performed in those with incomplete genotype. The gene founder effect was analyzed by microsatellite studies. Patients were divided into six genotypes (Null; A: <2%; B: 3-7%; C: >20% of residual enzymatic activity (EA); D: unknown EA; E: incomplete genotype). Results: Targeted methodologies defined genotype in 87.6% of classical and in 80% of NC patients and the addition of sequencing in 100 and 83.5%, respectively. The most frequent mutations were p.V281L (26.6% of alleles), IVS2-13A/C>G (21.1%), and p.I172N (7.5%); seven rare mutations and one novel mutation (p.E351V) were identified. Gene founder effect was observed in all but one (p.W19X) mutation. Null, A, B, and C genotypes correlated with SW (88%), SW (70%), SV (98%), and NC forms (100%), respectively. In group D, the p.E351V mutation correlated with classical form and group E comprised exclusively NC-patients. ACTH-stimulated 17OHP level of 44.3 ng/mL was the best cutoff to identify NC-patients carrying severe mutations. Conclusions: We identified a good genotype-phenotype correlation in CAH, providing useful data regarding prediction of disease´s severity; moreover, we suggest that ACTH-stimulated 17OHP levels could predict carrier status for severe mutations. Sequencing is essential to optimize molecular diagnosis in Brazilian CAH patients.
Molecular Genetics and Metabolism, 2006
More than 90% of congenital adrenal hyperplasia (CAH) cases are caused by 21-hydroxylase deWciency. In this study, the CYP21 gene was genotyped in 56 Portuguese unrelated patients with clinical symptoms of 21-hydroxylase deWciency, in a total of 112 independent alleles. CYP21A2 mutations were identiWed in 99.1% of the alleles. The most common point mutation was 1688G > T (25.9%). A previously unreported partial gene conversion, extending from exon 1 to 7, was found in 16.1% of the alleles, in most cases associated to the mutation 1688G > T in the other chromosome, and in patients with nonclassical CAH. Other three distinct partial gene conversions were also identiWed, with lower frequencies: one extends from exon 1 to 3 and the others from exons 3 to 7 and 3 to 8. Two novel mutations were identiWed in two salt-wasting patients: a putative splicing mutation, IVS2 + 5G > A, and the transition 2557C > T, that gives rise to the nonsense mutation R445X. Seven point mutations and a partial gene conversion were responsible for 88 of the studied disease causing alleles, and the overall concordance between genotype and phenotype was 92.9%. With this study the molecular basis of CAH was characterized, for the Wrst time, in Portuguese patients, providing useful results for clinicians in terms of prediction of disease severity, genetic and prenatal counseling.
Brazilian Journal of Medical and Biological Research, 2003
Deficiency of 21-hydroxylase is the most common form of congenital adrenal hyperplasia (CAH-21OH). We determined by allele-specific PCR the frequency of microconversion in the CYP21A2 gene in 50 Brazilian patients with the classical (salt wasting: SW and simple virilizing: SV) forms and nonclassical (NC) form of CAH-21OH and correlated genotype with phenotype. Genotypes were classified into three mutation groups (A, B, and C) based on the amount of enzymatic activity in in vitro studies using adrenal cells. In 94 unrelated alleles, we diagnosed 76% of the affected alleles after screening for 7 microconversions. The most frequent point mutations observed in this series were I172N (19%), V281L (18%), and IVS2,A/C>G,-12 (15%). In the SW form, the most frequent mutation was IVS2,A/C>G,-12 (38%), in the SV form it was I172N (53%), and in the NC form it was V281L (57.7%). We observed a good correlation between genotype and phenotype. Discordance between genotype and phenotype was found in one SV patient with a mild mutation in one of the alleles (R356W/V281L). However, we cannot rule out the presence of an additional mutation in these alleles. We also observed a good correlation of genotype with 17α-hydroxyprogesterone, testosterone, and androstenedione levels. The severity of external genitalia virilization correlated with the severity of mutation. In conclusion, the frequencies described in the present study did not differ from worldwide studies, including the Brazilian population. The few differences observed may reflect individual sample variations. This new Brazilian cohort study suggests the presence of new mutations in Brazilian patients with different forms of CAH-21OH.
Clinica Chimica Acta, 2009
Background: More than 90% of cases of congenital adrenal hyperplasia (CAH) are caused by a steroid 21hydroxylase deficiency. Approximately 75% of the defective CYP21A2 genes are generated through an intergenic recombination with the neighboring CYP21A1P pseudogene. These 2 duplicated genes share a 98% nucleotide sequence homology. Therefore, precisely identifying the CYP21A2 gene in CAH patients is absolutely necessary. Methods: We describe an established PCR-based amplification method, a denaturing high-performance liquid chromatography (DHPLC) analysis, to directly identify 11 different mutations commonly appearing in the CY-P21A1P gene. Among these 11 mutations, 9 are found in CAH patients and 2 created mutations were from normal individuals. Results: From the DHPLC analysis using 6 fragments of amplicons, the elution profiles of the 11 mutation sites were successfully used to distinguish these common disease-causing mutations of the CYP21A2 gene. Based on this resolution, we were able to rapidly search existing sequences of mutations in the CYP21A1P gene for this malady. Conclusion: DHPLC is an efficient and specific means to undertake such a program for screening patients with CAH caused by defects of the CYP21A2 gene resulting from the neighboring CYP21A1P pseudogene.
Development of CYP21A2 Genotyping Assay for the Diagnosis of Congenital Adrenal Hyperplasia
Molecular diagnosis & therapy, 2017
Steroid 21-hydroxylase deficiency due to CYP21A2 gene mutations represents more than 90% of all congenital adrenal hyperplasia cases. This deficiency is screened by measuring levels of 17-hydroxyprogesterone, which may vary, causing false positive or false negative results. In order to assist the diagnosis, molecular methodologies have been employed. This work aimed to perform genotyping assays to detect mutations in the CYP21A2 gene and compare the findings with other population studies. The SNaPshot assay was developed to simultaneously detect 12 frequent point mutations in the CYP21A2 gene (p.Arg409Cys, p.Gln319Ter, p.Arg357Trp, p.Leu308PhefsTer6, p.Val237Glu, IVS2-13A/C > G, p.Ile173Asn, p.Pro31Leu, p.Pro454Ser, p.Val282Leu, p.Gly111ValfsTer21 and p.His63Leu). The direct sequencing and multiplex ligation-dependent probe amplification assays were used to confirm point mutations present in the developed method. The latter was also used to search large deletions and gene convers...
Clinical Chemistry and Laboratory Medicine, 2010
Congenital adrenal hyperplasia (CAH) is characterized by impaired biosynthesis of cortisol. 21hydroxylase deficiency is the most common cause of CAH affecting 1 in 10000-15000 live births over the world. The frequency of the disorder is very high in Iran due to frequent consanguineous marriages. Although biochemical tests are used to confirm the clinical diagnosis, molecular methods could help to define accurate diagnosis of the genetic defect. Recent molecular approaches such as polymerase chain reaction based methods could be used to detect carriers and identify different genotypes of the affected individuals in Iran which may cause variable degrees of clinical expression of the condition. Molecular tests are also applied for prenatal diagnosis, and genetic counseling of the affected families. Here, we are willing to delineate mechanisms underlying the disease, genetic causes of CAH, genetic approaches being used in the country and recommendations for health care improvement on the basis of the molecular and clinical genetics to control and diminish such a high prevalent disorder in Iran. Also, the previous studies on CAH in Iran are gathered and a diagnostic algorithm for the genetic causes is proposed.