Severe 21-hydroxylase Deficiency Research Articles

Mechanisms, diagnosis and treatment of infertility in men born with severe 21-hydroxylase deficiency

Mechanisms, diagnosis and treatment of infertility in men born with severe 21-hydroxylase deficiency

Antenatal glucocorticosteroids treatment: mechanisms of child healths programming

Synthetic glucocorticoids are widely used in pregnancies at risk of preterm delivery and in pregnant women at risk of having a child with severe 21-hydroxylase deficiency. The positive effects of reducing mortality in preterm and virilisation in girls with congenital adrenal hyperplasia are now unquestionable. The adrenogenital syndrome responding to 21-hydroxylase deficiency is a common, potential fatal disease. Its incidence calculated on the basis of neonatal screening data makes 1 case for 14000 live newborns among the worldwide population, 1 for 9638 – In Russia. DEX passes through the placenta and decreases fetal ACTH production thereby suppressing the fetal production of androgens. The prenatal treatment does not preclude from a life-long treatment in future and it is not prevention of a salt-losing syndrome at the postnatal period, and dexamethasone safety in relation to cognitive development of children prenatally treated with dexamethasone is still up for debate. Adding to the concern is the fact that the doses of DEX that the fetus is exposed to are estimated to be 60 times the normal fetal cortisol level. The glucocorticoid and the mineralocorticoid receptors are highly expressed in the hippocampus, amygdala, and prefrontal cortex. These areas, important for executive functioning, emotional regulation, and memory, are vulnerable to high doses of GCs. Most experimental data from animal have shown that prenatal exposure to synthetic glucocorticoids programs the foetal HPA and may lead to altered susceptibility to metabolic and cardiovascular disease i.e. metabolic syndrome, high blood pressure. Prenatal glucocorticoid exposure also leads to modification of HPAassociated behaviours and cognition.

CYP21A2 p.E238 Deletion as Result of Multiple Microconversion Events

More than 90% of congenital adrenal hyperplasia (CAH) cases are associated with mutations in the 21-hydroxylase gene (CYP21A2) in the HLA class III area on the short arm of chromosome 6p21.3. The major part of disease-causing mutations in CYP21A2 alleles are CYP21A1P-derived sequence transferred to the active gene by macroconversion or microconversion events. Only around 5% of all disease-causing CYP21A2 alleles harbor rare mutations that do not originate from the pseudogene. A complete list of all reported CYP21A2 mutations can be found in the CYP21A2 database created by the Human Cytochrome P450 (CYP) Allele Nomenclature Committee (http://www.imm.Ki.se/CYPalleles/cyp21.htm). In this report, we describe clinical and genetic findings regarding an Italian woman suffering from a classic salt-wasting form of CAH due to a severe 21-hydroxylase deficiency. A complex genetic family study was performed including a prenatal diagnosis. The patient was found to be heterozygous for p.I172N (exon 4), p.E238del (exon 6), p.M239K (exon 6), and p.F306insT (exon 7) mutations and homozygous for p.I236N (exon 6) and p.V237E (exon 6) mutations. The deletion of glutamic acid 238 is a new mutation not reported before in the literature. CYP21A2 genotyping has become a valuable complement to biochemical CAH investigation. We highlight the contribution of molecular genetic advancements to the clinical management of patients with 21-hydroxylase deficiency.

Carrier detection and prenatal diagnosis of congenital adrenal hyperplasia must identify ‘apparently mild’ CYP21A2 alleles which associate neonatal salt‐wasting disease

Couples at risk of severe congenital adrenal hyperplasia (CAH) may be offered prenatal treatment or preimplantation diagnosis. However, proper genetic counselling requires the accurate identification of apparently 'mild alleles' in partners of CAH-carriers/patients. CYP21A2 gene analyses were performed in 255 patients with severe 21-hydroxylase deficiency (21-OHD), 94 with mild 21-OHD, 752 parental samples, 233 clinically unaffected partners and 253 historic DNA samples. GENSCAN and ClustalX2.0 software were used for in silico analyses, and Epidat 3.1 software for statistical calculations. Twenty-seven partners were carriers of p.Val282Leu (alias p.Val281Leu, allele frequency 11.7%, 7.4-16.1). 'Val282Leu alleles' were detected in 30 patients with salt-wasting (SW) disease, 21 with other pseudogene-derived and rare coding cis severe mutations, and 9 without. These CYP21A2 genes were compared to those of 94 fully characterized patients with mild deficiency carrying p.Val282Leu in compound heterozygosity with a severe allele. A rare intronic variant, c.292+5G>A, was detected in the nine 'severe Val282Leu alleles' and that was not seen in mild p.Val282Leu alleles, in other deficient alleles or in normal chromosomes. The in silico documented effect on splicing and the clinical association (p < 0.0001) confirmed p.Val282Leu; c.292+5G>A as a severe allele. As only severe alleles require clinical intervention, CAH-carrier detection of p.Val282Leu should be followed by the analysis of c.292+5G>A.

A new CYP21A2 nonsense mutation causing severe 21-hydroxylase deficiency

Congenital adrenal hyperplasia (CAH) is an autosomal recessive disorder caused primarily by defects in the steroid 21-hydroxylase gene (CYP21A2). The CYP21A2 gene is located in the HLA class III region on the short arm of chromosome 6p21.3, along with an inactive pseudogene, CYP21A1P, that is 98% homologous with CYP21A2 in its coding sequence. Most mutations found in the CYP21A2 gene are normally present in the pseudogene, implying that recombination events (microconversion) between these two genes may lead to the transfer of mutations from the pseudogene to the functional gene. Approximately only 5% of all CYP21A2 alleles causing disease harbour rare mutations not originating from the pseudogene. However, detection of these rare and spontaneous mutations has continued to expand worldwide. In this report, we describe the clinical and genetic findings in a Romanian newborn suffering from classic salt wasting form of CAH due to severe 21-hydroxylase deficiency.

Steroid 21-hydroxylase (P450c21): a new allele and spread of mutations through the pseudogene.

Lesions in the gene encoding the adrenal enzyme steroid 21-hydroxylase (P450c21) result in defective adrenal cortisol synthesis, often accompanied by aldosterone deficiency. The symptoms range from severe neonatal disease to inconspicuous symptoms in adulthood depending on the nature of the mutations. The 21-hydroxylase gene is present in close proximity to a highly homologous pseudogene, and both genes show variation in copy number between individuals. For complete DNA sequence characterization, we have applied selective polymerase chain reaction amplification and direct sequencing of all full-length steroid 21-hydroxylase genes present in individuals. Using healthy individuals with only one remaining steroid 21-hydroxylase allele as normal references, a new allele was found in two siblings, in whom clinical and laboratory findings demonstrated moderate enzyme deficiency. Full-length sequencing of this allele displayed an Arg 484 to Pro codon change in exon 10, in the same position as a previously identified GG to C mutation found in a patient with severe 21-hydroxylase deficiency. Arg 484 is located within a stretch of amino acids that are highly conserved between mammalian 21-hydroxylases. The finding of the presently reported 21-hydroxylase allele indicates that the GG to C mutation from the severely affected patient has arisen by a two-step mechanism, consisting of a G to C transversion accompanied by an adjacent G deletion. When sequencing 26 pseudogenes, both these mutations, which are not present in the pseudogenes hitherto reported, were found at low frequency together with a number of other polymorphisms. Thus, also rare mutations can spread via the pseudogene and can therefore be expected to arise independently in unrelated individuals.

Molecular biology of disorders of sex differentiation.

Sexual ambiguity can be a difficult and sometimes confusing diagnostic problem in children. Recent developments in molecular biology have provided the opportunity to analyze the gene responsible for testicular determination, SRY, the androgen receptor gene and the gene encoding the cP450 enzyme specific for 21-hydroxylation, CYP21B, whose defects are responsible for congenital adrenal hyperplasia. Southern-blotting studies and PCR analyses of SRY, androgen receptor and CYP21B genes can be routinely used for the direct diagnosis of gonadal dysgenesis, androgen insensitivity syndromes and congenital adrenal hyperplasia, respectively. In sex-reversed XY females, several de novo mutations or deletions in the SRY gene have been reported. Defects in the human androgen receptor cause a spectrum of defects in male phenotypic sexual development associated with abnormalities in the receptor protein. Analyses of the androgen receptor gene structure have identified the causative mutation in some families: mutations that result in large-scale alterations of the structure of the androgen receptor, mRNA or gene mutations that alter the primary structure of the androgen receptor protein and mutations that alter the level of mRNA. The diversity of clinical phenotypes, apparent in 21-hydroxylase deficiency, is paralleled by a considerable degree of mutational heterogeneity in the CYP21 gene locus. Various changes causing severe 21-hydroxylase deficiency have been reported: point mutations, gene conversions and gene deletions. In conclusion, substantial progress has been made elucidating genetic defects causing sex reversal in XY females, the androgen insensitivity syndrome and congenital adrenal hyperplasia. Molecular genetics can also be applied for carrier identification and prenatal diagnosis.