Exome and genome sequencing: a revolution for the discovery and diagnosis of monogenic disorders

Massively parallel DNA sequencing has revolutionized analyses of human genetic variation. From having been out of reach for individual research groups and even more so for clinical diagnostic laboratories until recently, it is now possible to analyse complete human genomes within reasonable time frames and at a reasonable cost using technologies that are becoming increasingly available. This represents a huge advance in our ability to provide correct diagnoses for patients with rare inherited disorders and their families. This paradigm shift is especially dramatic within the area of monogenic disorders. Not only can rapid and safe diagnostics of virtually all known single-gene defects now be established, but novel causes of disease in previously unsolved cases can also be identified, illuminating novel pathways important for normal physiology. This greatly increases the capability not only to improve management of rare disorders, but also to improve understanding of pathogenetic mechanisms relevant for common, complex diseases.

Identification of a duplication within the GDF9 gene and novel candidate genes for primary ovarian insufficiency (POI) by a customized high-resolution array comparative genomic hybridization platform

STUDY QUESTION

Can high-resolution array comparative genomic hybridization (CGH) analysis of DNA samples from women with primary ovarian insufficiency (POI) improve the diagnosis of the condition and identify novel candidate genes for POI?

SUMMARY ANSWER

A mutation affecting the regulatory region of growth differentiation factor 9 (GDF9) was identified for the first time together with several novel candidate genes for POI.

WHAT IS KNOWN ALREADY

Most patients with POI do not receive a molecular diagnosis despite a significant genetic component in the pathogenesis.

STUDY DESIGN, SIZE, DURATION

We performed a case–control study. Twenty-six patients were analyzed by array CGH for identification of copy number variants. Novel changes were investigated in 95 controls and in a separate population of 28 additional patients with POI. The experimental procedures were performed during a 1-year period.

PARTICIPANTS/MATERIALS, SETTING, METHODS

DNA samples from 26 patients with POI were analyzed by a customized 1M array-CGH platform with whole genome coverage and probe enrichment targeting 78 genes in sex development. By PCR amplification and sequencing, the breakpoint of an identified partial GDF9 gene duplication was characterized. A multiplex ligation-dependent probe amplification (MLPA) probe set for specific identification of deletions/duplications affecting GDF9 was developed. An MLPA probe set for the identification of additional cases or controls carrying novel candidate regions identified by array-CGH was developed. Sequencing of three candidate genes was performed.

MAIN RESULTS AND THE ROLE OF CHANCE

Eleven unique copy number changes were identified in a total of 11 patients, including a tandem duplication of 475 bp, containing part of the GDF9 gene promoter region. The duplicated region contains three NOBOX-binding elements and an E-box, important for GDF9 gene regulation. This aberration is likely causative of POI. Fifty-four patients were investigated for copy number changes within GDF9, but no additional cases were found. Ten aberrations constituting novel candidate regions were detected, including a second DNAH6 deletion in a patient with POI. Other identified candidate genes were TSPYL6, SMARCC1, CSPG5 and ZFR2.

LIMITATIONS, REASONS FOR CAUTION

This is a descriptive study and no functional experiments were performed.

WIDER IMPLICATIONS OF THE FINDINGS

The study illustrates the importance of analyzing small copy number changes in addition to sequence alterations in the genetic investigation of patients with POI. Also, promoter regions should be included in the investigation.

STUDY FUNDING/COMPETING INTEREST(S)

The study was supported by grants from the Swedish Research council (project no 12198 to A.W. and project no 20324 to A.L.H.), Stockholm County Council (E.I., A.W. and K.R.W.), Foundation Frimurare Barnhuset (A.N., A.W. and M.B.), Karolinska Institutet (A.N., A.L.H., E.I., A.W. and M.B.), Novo Nordic Foundation (A.W.) and Svenska Läkaresällskapet (M.B.). The funding sources had no involvement in the design or analysis of the study. The authors have no competing interests to declare.

TRIAL REGISTRATION NUMBER

Not applicable.

Suboptimal psychosocial outcomes in patients with congenital adrenal hyperplasia: epidemiological studies in a nonbiased national cohort in Sweden

CONTEXT

Congenital adrenal hyperplasia (CAH), CYP21A2 deficiency, results in cortisol and aldosterone deficiency and increased production of androgens, with a good genotype phenotype correlation.

OBJECTIVE

The objective of the investigation was to study psychosocial outcomes in relation to clinical severity, CYP21A2 genotype, in men and women.

DESIGN

This was an epidemiological study with a matched case control design.

SETTING

The setting of the study was all known CAH patients in Sweden.

PARTICIPANTS

Five hundred eighty-eight patients, more than 80% with known severity of CAH, and 100 controls per patient matched for sex, year, and place of birth participated in the study.

MAIN OUTCOME AND MEASURES

Proxies for quality of life were selected: level of education, employment, income, sick leave, disability pension, marriage, and children.

RESULTS

Women with salt-wasting (SW) CAH had completed primary education less often [odds ratio (OR) 0.3], not explained by neonatal salt crisis or hypoglycemia because the men did not differ from controls. Men and women in the less severe I172N genotype group were more likely to have an academic education (OR 1.8). SW women were more likely to have an income in the top 20th percentile (OR 2.0). Both men and women had more disability pension (OR 1.5) and sick leave (OR 1.7). The men more often had long-lasting employment (OR 3.1). Men were more often (OR 1.6) and women were less often married (OR 0.7). Patients had children less often (OR 0.3).

CONCLUSIONS

This study shows important outcome differences regarding education; employment; marriage and fertility, depending on sex; and severity of CAH. The mechanisms behind this and the increased risk for sick leave or disability pension in both men and women should be identified to improve medical and psychological care.

No mutations in the PSMC3IP gene identified in a Swedish cohort of women with primary ovarian insufficiency

Ovarian dysfunction before the age of 40 years, characterized by hypergonadotropic hypogonadism and presenting with either primary or secondary amenorrhea, is called primary ovarian insufficiency (POI). POI has a significant genetic component, but the specific genetic cause is often unknown. A novel candidate gene for POI, PSMC3IP, has recently been identified. The aim of this study was to investigate a group of patients with POI for possible PSMC3IP mutations. Therefore, DNA samples from 50 patients with POI of primarily Swedish origin were used in the study, 27 with secondary amenorrhea (median age of diagnosis 23 years) and 23 with primary amenorrhea. Control material consisting of DNA samples from 95 women without POI was used for investigation of novel sequence variants. All exons and intron/exon boundaries of the PSMC3IP gene were analyzed by PCR and sequencing. As a result, no pathogenic mutation in the PSMC3IP gene was detected in the cohort. A previously unreported variant, NM_016556.3:c.337+33A>G, was detected in heterozygous form in 1 patient with secondary amenorrhea, likely constituting a normal variant. Two reported single nucleotide polymorphisms were detected in the cohort at the expected frequency. In conclusion, PSMC3IP gene mutations are not common causes of POI in this Swedish cohort.

A sequence variation in 3'UTR of CYP21A2 gene correlates with a mild form of congenital adrenal hyperplasia

BACKGROUND

Congenital adrenal hyperplasia (CAH) is mainly caused by the deficiency of the 21-hydroxylase enzyme coded by the CYP21A2 gene. However, some alleles in the non-classical form (NC-CAH) remain without identified mutations, suggesting the involvement of regulatory regions.

AIM

Our objective was to study an allele carrying the variant *13 G>A in the 3'UTR of the CYP21A2 gene identified in some patients with a mild form of NC-CAH in order to verify the possible implication of this variation with the phenotype observed.

SUBJECTS AND METHODS

Among all the subjects in whom the CYP21A2 gene was analyzed, 14 patients and 7 relatives heterozygous or homozygous for the *13 G>A substitution in 3'UTR were selected. Sequencing of DNA, genotyping, multiplex ligation-dependent probe amplification (MLPA), in vitro studies and bioinformatic analysis were performed.

RESULTS

The haplotype of the *13 G>A allele was identical in all the subjects with a monomodular structure composed by one C4A gene and one CYP21A2 gene without a second module with the CYP21A1P pseudogene. No other concomitant mutations were found in the region extending from 3 kb in the promoter and encompassing the polyadenylation signal. Both bioinformatic analysis and in vitro studies predicted an alteration of the RNA folding and expression, but no miRNA target sequences were found in this region.

CONCLUSIONS

The identification of a substitution in the 3'UTR of the gene associated with a mild form of NC-CAH suggests the importance of analyzing the CYP21A2 untranslated regions to better characterize and treat this subgroup of patients.

Pubertal androgenization and gonadal histology in two 46,XY adolescents with NR5A1 mutations and predominantly female phenotype at birth

OBJECTIVE

Most patients with NR5A1 (SF-1) mutations and poor virilization at birth are sex-assigned female and receive early gonadectomy. Although studies in pituitary-specific Sf-1 knockout mice suggest hypogonadotropic hypogonadism, little is known about endocrine function at puberty and on germ cell tumor risk in patients with SF-1 mutations. This study reports on the natural course during puberty and on gonadal histology in two adolescents with SF-1 mutations and predominantly female phenotype at birth.

DESIGN AND METHODS

Clinical and hormonal data and histopathological studies are reported in one male and one female adolescent with, respectively, a nonsense mutation (c.9T>A, p.Tyr3X) and a deletion of the first two coding exons (NCBI36/hg18 Chr9:g.(126306276-126307705)_(126303229-126302828)del) of NR5A1, both predicted to fully disrupt gene function.

RESULTS

LH and testosterone concentrations were in the normal male range, virilization was disproportionate to the neonatal phenotype. In the girl, gonadectomy at 13 years revealed incomplete spermatogenesis and bilateral precursor lesions of testicular carcinoma in situ. In the boy, at the age of 12, numerous germ cells without signs of malignancy were present in bilateral testicular biopsy specimen.

CONCLUSIONS

In SF-1 mutations, the neonatal phenotype poorly predicts virilization at puberty. Even in poorly virilized cases at birth, male gender assignment may allow spontaneous puberty without signs of hypogonadotropic hypogonadism, and possibly fertility. Patients with SF-1 mutations are at increased risk for malignant germ cell tumors. In case of preserved gonads, early orchidopexy and germ cell tumor screening is warranted. The finding of premalignant and/or malignant changes should prompt gonadectomy or possibly irradiation.

Partial deletion of the NR5A1 (SF1) gene detected by synthetic probe MLPA in a patient with XY gonadal disorder of sex development

Steroidogenic factor 1 (SF1, officially NR5A1) is a nuclear receptor involved in adrenal and gonadal development. NR5A1 mutations have been identified in patients with various forms of 46,XY disorders of sex development (DSD), including complete gonadal dysgenesis with or without adrenal insufficiency, mild testicular dysgenesis with ambiguous external genitalia or female external genitalia with clitoromegaly, and penoscrotal hypospadias. We developed a synthetic probe set for MLPA analysis of the NR5A1 gene covering its 7 exons and analyzed 20 patients with 46,XY gonadal DSD in whom analyses failed to identify a genetic cause. We identified a partial NR5A1 deletion affecting exons 2 and 3, leading to NR5A1 haploinsufficiency in 1 patient presenting with female external genitalia with clitoromegaly, absence of a uterus, and mildly dysgenetic testes. This is the first partial NR5A1 gene deletion identified by MLPA in a patient with 46,XY gonadal DSD. This finding stresses the importance of investigating copy number changes, even at the exon level, in genes involved in gonadal DSD. As NR5A1 mutations can cause a wide spectrum of DSD with relatively high frequency, the analysis of the NR5A1 gene by MLPA is quite important and should be extended to larger groups of patients.

Disorders of sex development

Infants born with ambiguous genitalia represent a complex clinical challenge. A systematic clinical investigation aims at determining the hormone production and which anatomical structures are present in order to understand at what level the sex differentiation has been affected; chromosomal, gonadal or hormonal synthesis and action levels. The increased genetic knowledge in the field has opened up new diagnostic possibilities. Sex development requires the balanced and sequential activation of transcription factors, signaling molecules and hormones. It has recently been shown that not only testis but also normal ovarian development is an active process. Genes involved in gonadal disorders of sex development often act in a gene dosage-dependent manner, with different effects in XY or XX embryos. The management of patients with disorders of sex development, including decisions about sex of rearing, must be carried out by a specialized multidisciplinary team and include an extended genetic investigation as well as psychological considerations.

Inhibition of CYP21A2 enzyme activity caused by novel missense mutations identified in Brazilian and Scandinavian patients

BACKGROUND

Most patients with 21-hydroxylase deficiency carry CYP21A1P-derived mutations, but an increasing number of novel and rare mutations have been reported in disease-causing alleles.

OBJECTIVE

Functional effects of three novel (p.G56R, p.L107R, p.L142P) and one recurrent (p.R408C) CYP21A2 mutations were investigated. The degree of enzyme impairment caused by p.H62L alone or combined to p.P453S was also analyzed.

DESIGN

The study included 10 Brazilian and two Scandinavian patients. To determine the deleterious role of each mutant protein, in vitro assays were performed in transiently transfected COS-1 cells. For a correct genotype-phenotype correlation, the enzymatic activities were evaluated toward the two natural substrates, 17-hydroxyprogesterone and progesterone.

RESULTS

Low levels of residual activities obtained for p.G56R, p.L107R, p.L142P, and p.R408C mutants classified them as classical congenital adrenal hyperplasia mutations, whereas the p.H62L showed an activity within the range of nonclassical mutations. Apparent kinetic constants for p.H62L confirmed the nonclassical classification as the substrate binding capacity was within the same magnitude for mutant and normal enzymes. A synergistic effect was observed for the allele bearing the p.H62L+p.P453S combination because it caused a significant reduction in the enzymatic activity.

CONCLUSIONS

We describe the functional analysis of five rare missense mutations identified in Brazilian and Scandinavian patients. The p.G56R, p.L107R, and p.L142P are reported for the first time. Most probably these novel mutations are closer to null than the p.I172N, but for the p.G56R, that might not be the case, and the p.H62L is definitely a nonclassical mutation.

The reproductive tissue specific cystatin subgroup of genes: expression during gonadal development in wildtype and testatin knockout animals

Testatin has been implicated in fetal testis development due to its restricted expression in pre-Sertoli cells immediately after the onset of Sry gene expression. However, testatin knockout mice showed normal testis development and fertility. We investigated the spatial and temporal expression pattern of the Cres/testatin subgroup of genes, including the novel gene Cstl1/Cres4, in fetal mouse gonads and in adult testis, epididymis and ovary. The genes are related to the family 2 cystatins of protease inhibitors. Using real-time PCR and in situ hybridization we could show that 4 subgroup genes, testatin, CstSC, CstTE-1/Cres3 and Cres are expressed in fetal testis. We also confirmed the expression of testatin, CstE2, CstSC, CstTE-1/Cres3, Cres, CstT and Cstl1/Cres4 in adult testis and CstE2, CstTE-1/Cres3, Cres and CstE1/Cres2 in adult epididymis. In testatin knockout animals, the expression of CstE2 was heavily downregulated in adult testis, but not in adult epididymis, compared to wildtype controls. In conclusion, an explanation for the lack of phenotype in testatin knockout mice could be functional redundancy with another member of the Cres/testatin subgroup. The most likely candidate/s would be CstSC, CstTE-1/Cres3 or Cres as they are expressed in the fetal testicular tubules in early testis differentiation together with testatin.

Functional studies of two novel and two rare mutations in the 21-hydroxylase gene

Congenital adrenal hyperplasia (CAH) is most commonly due to 21-hydroxylase deficiency and presents with a wide spectrum of clinical manifestations, from prenatal virilization and salt-wasting in the neonatal period to precocious pubarche and late-onset hyperandrogenic symptoms during adulthood. A limited number of mutations account for the majority of all mutated alleles, but a growing number of rare mutations are responsible for the disease in some patients. By sequence analysis of the CYP21A2 gene, we identified two novel (I171N and L446P) and two rare (R341P and R426H) mutations in seven Italian patients with CAH. One of the patients was diagnosed with mild non-classical CAH and was found to be a compound heterozygote (I171N/V281L), while all other patients showed severe phenotypes with latent or manifest salt-wasting. The residual activities measured after expression of the four mutant enzymes in COS-1 cells were all below 1% towards both natural substrates (17-OH-progesterone and progesterone) compared with the wild-type protein. All four mutations are, thus, associated with severe enzyme deficiency and are predicted to cause classic CAH if found in trans with other mutations causing severe enzyme deficiency.

Functional analysis of two recurrent amino acid substitutions in the CYP21 gene from Italian patients with congenital adrenal hyperplasia

Congenital adrenal hyperplasia (CAH) is most commonly due to 21-hydroxylase deficiency and presents a wide spectrum of clinical manifestations from a severe classical form to a milder late-onset form with a variable severity of hyperandrogenic symptoms. A limited number of mutations account for the majority of the mutated alleles, but additional rare mutations are responsible for the symptoms in some patients. By CYP21 gene analysis, we identified a chimeric CYP21P/CYP21 gene with the fusion breakpoint downstream of the common P30L mutation as well as a GCC to ACC change at codon 15 (A15T) in two subjects with classical CAH and a CCC to TCC change at codon 482 (P482S) in seven subjects referred for nonclassical CAH, precocious pubarche, menstrual irregularities, or hypertrichosis. The two amino acid substitutions were reconstructed by in vitro site-directed mutagenesis, the proteins were transiently expressed in COS-1 cells, and enzyme activity toward the two natural substrates (17-hydroxyprogesterone and progesterone) was determined. The A15T mutant exhibited no significant difference in activity compared with the wild-type protein, whereas the P482S mutation reduced enzyme activity to 70% of normal. This impairment of activity was confirmed in vivo by detection of heterozygote carriers by the ACTH test.

Neonatal screening for congenital adrenal hyperplasia: 17-hydroxyprogesterone levels and CYP21 genotypes in preterm infants

OBJECTIVE

Neonatal screening for congenital adrenal hyperplasia (CAH) among preterm infants is complicated by the fact that healthy preterm infants have higher levels of 17-hydroxyprogesterone (17-OHP) than term infants, resulting in a higher false-positive rate. Even when gestational age-related cutoff levels after ether extraction were used, the false-positive cases primarily comprised preterm infants. The aim of the study was to optimize the procedure for neonatal screening for CAH in preterm infants.

METHODS

The 17-OHP levels in 6200 preterm infants were correlated to the gestational age. We also calculated the number of recalls for different putative cutoff levels of the 17-OHP by direct assay and after extraction in 1275 preterm infants who represented the most elevated cases in a population of approximately 30 000 preterm infants. The CYP21 genotypes and screening levels were determined in the 12 preterm infants with CAH diagnosed since the start of screening. The effect of possible interfering factors such as gestational age, neonatal stress, and prenatal glucocorticoid treatment for pulmonary maturation was studied.

RESULTS

The extraction procedure did not significantly improve the sensitivity or specificity of the screening, whereas it delayed the day of recall from 8 to 13 days (median). We could not demonstrate any systematic influence of the studied stress factors or the prenatal glucocorticoid treatment on the 17-OHP screening levels. In the patients with CAH, the 17-OHP levels correlated better with disease severity than with the degree of prematurity.

CONCLUSIONS

On the basis of these results, we omitted the extraction step and changed the cutoff levels in the Swedish screening program for preterm infants. We chose to use a cutoff level of 400 nmol/L plasma in infants who were born before week 35 and 150 nmol/L for infants who were born in weeks 35 and 36. For detecting more patients, the cutoff level would have to be much lower, which would result in a number of false-positive tests that we consider to be unacceptably high. It is clear that neonatal screening cannot detect all infants with CAH. Some milder forms of the disease, just like in the past, will have to be diagnosed on the basis of clinical signs and symptoms.

CYP21 mutations in simple virilizing congenital adrenal hyperplasia

We studied the functional and structural effects of two unique missense mutations in CYP21 found in patients with simple virilizing congenital adrenal hyperplasia. The rare variants L300F and V281G were found in two girls who were each hemizygous for one of the mutations. Functional analysis after expression in COS-1 cells revealed that the mutant enzymes had reduced enzymatic activity for conversion of both 17-hydroxyprogesterone (L300F 9.5%, V281G 3.9% of normal) and progesterone (L300F 4.4%, V281G 3.9% of normal). Both mutant enzymes had an increased degradation in mammalian COS-1 cells compared to the normal protein, although the L300F variant affected the degradation pattern to a greater extent. Our data indicate that the residue L300 is important in maintaining normal structure of the 21-hydroxylase enzyme whereas mutations affecting V281 most likely cause impaired enzyme activity by interfering with a specific function(s) of the protein.

In vitro release of aldosterone and cortisol in human adrenal adenomas correlates to mRNA expression of steroidogenic enzymes for genes CYP11B2 and CYP17

Adenomas of the adrenal cortex cause different disorders depending on the main steroid synthesized and released. The aim of this research is to increase our understanding of the pathophysiology of steroidogenesis in adrenocortical disorders by comparing the release of steroids from adrenocortical adenomas in vitro with the messenger RNA (mRNA) expression of steroid synthesizing enzymes. Fourteen patients with adrenal tumors were included in the present study; nine were diagnosed with primary aldosteronism and three with Cushing's syndrome. Two patients had an adrenal tumor discovered on computed tomography (CT) during workup for an unrelated disease. Serum cortisol, plasma aldosterone, and urinary catecholamines were normal. Tissue was taken for in vitro steroid release, and aldosterone and cortisol in the medium after a 1-hour incubation were determined. Oligonucleotide probes with sequences complementary to mRNAs encoding for the steroid synthesizing enzymes 11 beta-hydroxylase (CYP11B1), 18-hydroxylase (CYP11B2), 17 alpha-hydroxylase (CYP17), and 21-hydroxylase (CYP21) were synthesized (Genset, Paris, France) and in situ hybridization was performed. Moderate expression of CYP11B2 and low expression of CYP11B1 were seen in the zona glomerulosa. The zona fasciculata of the control adrenals expressed a high signal of CYP11B1, whereas the expression of CYP11B2 was very low. There was considerable variation in aldosterone release from the aldosteronomas, whereas the tumors from the Cushing patients showed no detectable release of aldosterone. In contrast, tumors from patients with primary aldosteronism, Cushing's syndrome, and no hyperfunction all had the ability to synthesize and release cortisol in vitro. The highest cortisol release was found in tumors from patients with Cushing's syndrome, but also the nonhyperfunctioning tumors and some of the aldosteronomas released significant amounts of cortisol. The two patients with highest release of aldosterone in vitro showed the highest expression of CYP11B2 and the lowest expression of CYP11B1 and CYP17. The remaining aldosteronomas had low expression of CYP11B2, similar to the two other groups. Expression of CYP11B1 was high as expected in the Cushing adenomas, but also the two nonhyperfunctioning tumors and some of the aldosteronomas showed a moderate expression. Adenomas from Cushing's syndrome, nonhyperfunctioning adenomas, and some of the aldosterone-producing adenomas had moderate to high expression of CYP17. This paper presents new means for functional characterization of adrenocortical tumors. Diagnosis of an aldosteronoma is often difficult, and with the advent of these methods it is possible to determine the functional capacity of a tumor, once it is removed. This is of special interest if the patient remains hypertensive postoperatively, and it is not clear whether the patient indeed had a functioning tumor.

A novel mutation (N233K) in the transactivating domain and the N756S mutation in the ligand binding domain of the androgen receptor gene are associated with male infertility

OBJECTIVE

Resistance to androgens has been suggested as a possible cause of male infertility. This hypothesis is based mainly on binding studies in genital skin fibroblasts but the molecular evidence is sparse.

DESIGN

Molecular studies of the androgen receptor gene were performed in 10 azoo- or oligozoospermic men, presenting with clinical signs of low androgen activity-poor virilization and high serum LH despite elevated testosterone levels, but without genital malformations.

PATIENTS

Ten men with serum LH >10 IU/l and testosterone >30 nmol/l as well as a low sperm concentration < 20 x 106/ml.

MEASUREMENTS

Genomic DNA was prepared from peripheral leucocytes and PCR-amplification of the coding region of androgen receptor was performed, followed by direct sequencing. Identified mutations were reconstructed by site-directed mutagenesis and the functional properties of the mutants were analysed, using transient expression in COS-1 cells and subsequent transactivation assays. Hormone binding assays were performed in genital skin fibroblasts from the patients.

RESULTS

Two of the 10 men were shown to have a mutation in the androgen receptor gene. Subject 1, who presented with azoospermia, serum testosterone (T) 50 nmol/l and LH 20 IU/l, had a mutation in exon 1, changing amino acid asparagine 233 to lysine (N233K). In fibroblasts cultured from genital skin, the receptor affinity for 5alpha-dihydrotestosterone (DHT) was normal as compared to healthy controls, but the receptor-hormone complex was thermolabile at 42 degrees C. Subject 2 exhibited severe oligozoospermia and a similar endocrine pattern (T = 50 nmol/l and LH = 25 IU/l). He had a mutation in exon 5 changing asparagine 756 to serine (N756S). The affinity for DHT in cultured genital fibroblasts from this patient was reduced. Transactivation was abnormal for both mutants, N233K reaching 46% and N756S 38% of wild type activity when stimulated with 10 nmol/l DHT.

CONCLUSIONS

Androgen receptor mutations may affect sperm production without resulting in genital malformations. Thus, in infertile men with a clinical presentation of poor androgen activity and an endocrine profile compatible with androgen resistance, mutations in the androgen receptor should be taken into consideration.

Incidence and clinical relevance of recurrent hepatitis C infection after orthotopic liver transplantation

From September 1988 to November 1992 318 liver transplants were performed at our hospital. Of these patients 68 had end-stage cirrhosis due to non-A, non-B, hepatitis, 44 of whom (64.7%) had hepatitis C virus RNA in the serum. Of this subgroup 35 patients (79.5%) were also anti-HCV positive. Postoperatively most recipients remained anti-HCV positive and after 1 year more than 90% had HCV RNA in the serum. About 40% developed a mild, chronic hepatitis and 50% were carriers of HCV without histopathological signs. Two patients suffered from a temporary severe acute hepatitis and one patient had a fulminant liver failure due to reinfection. In general, in liver recipients transplanted for end-stage HCV hepatitis there was a high incidence of reinfection with HCV. The clinical course, however, was less severe than in hepatitis B recurrence.

How can molecular biology contribute to the management of congenital adrenal hyperplasia?

The most common form of congenital adrenal hyperplasia is due to a deficiency of 21-hydroxylase (21OHD) activity and is caused by a mutation in the CYP21 gene. By genotyping patients, new and important information can be gained, including presence or absence of 21OHD in borderline cases, determining the severity of disease and identifying heterozygote carriers. Current management of patients with 21OHD involves administering sufficient glucocorticoids to suppress excess adrenal androgen secretion, but not so much that bone growth and mineralization are impaired. New management strategies have been proposed and include administering only substitution doses of corticosteroids and counteracting side-effects by administering an anti-androgen and aromatase inhibitor. Adrenalectomy has also been proposed. Further investigation into these approaches is necessary.

Response to treatment in patients with partial androgen insensitivity due to mutations in the DNA-binding domain of the androgen receptor

The androgen insensitivity syndrome is a disorder caused by deficient function of the androgen receptor, characterized by varying degrees of undermasculinization in karyotypic males. We have identified four mutations in the androgen receptor gene, in the region encoding the DNA-binding domain of the protein. Two mutations, R607X and R615G, were found in patients with complete insensitivity to androgens, whereas the other two, S578T and A596T, were found in patients with partial insensitivity. The functional consequences of the three missense mutations were assayed in vitro after transient expression of the receptors in COS cells. All mutants showed normal androgen binding but abnormal abilities to stimulate transcription of an androgen-responsive reporter gene. R615G abolished transactivation whereas S578T and A596T were partially malfunctional. The function of A596T, but not of S578T, was normalized at high androgen concentrations in vitro, reflecting the in vivo situation. Thus, patients with specific mutations in the DNA-binding domain of the androgen receptor may benefit from androgen treatment.

Preserved male fertility despite decreased androgen sensitivity caused by a mutation in the ligand-binding domain of the androgen receptor gene

Mutations in the androgen receptor gene are considered as incompatible with preservation of fertility and have been suggested as a cause of male infertility. Two adult brothers, referred because of gynecomastia and hormonal levels in serum indicating androgen insensitivity (high sex hormone-binding globulin, and LH levels, despite extremely high testosterone concentration), turned out to be relatives to a third young man, referred independently of the two others and exhibiting identical clinical and hormonal stigmata. In all three men, we found a C-->A substitution at position 2470 (exon 7) in the androgen receptor gene, leading to a Gln824Lys mutation in the ligand-binding domain of the receptor. Exploring the family history revealed that their grandfathers, on their mothers' side, were brothers; and the Gln824Lys mutation was also found in the one of them who was still alive. Binding studies with the mutant receptor in transfected COS-7 cells, with mibolerone as ligand, exhibited equal Kd (0.7 vs. 1.0 nmol/ L), IC50 (0.8 vs. 1.1 nmol/L), and maximum binding (7.1 vs. 8.9 fmol/ 10(6) cells), as compared with the wild-type (WT) receptor. In a chloramphenicol acetyl transferase trans-activation assay, the activity of the mutant receptor was identical to that of the WT, when the synthetic androgen R1881 was'used as a ligand; but with dihydrotestosterone, in concentrations up to 10 nmol/L, the activity of Gln824Lys mutated receptor was 10-62% of the WT variant. Thus, Gln824Lys mutation was found, both in vivo and in vitro, to cause slight impairment of receptor function but was compatible with preservation of male fertility. The patients inherited the mutation from their grandfathers through their mothers, and one of the young men possessing the mutation has fathered a daughter.

[Boy or girl? Molecular mechanisms in sex differentiation]

A growing number of factors have been recognized as crucial in sexual development, and many clinical conditions have become understandable as mutations in relevant genes have been identified. In some cases this has led to the development of DNA diagnostics, which can be of some aid in the workup of this type of patient. So far it is mainly more serious disorders which have been elucidated, thanks to the identification of extensive mutations in the key genes for sexual development. Exactly to what extent less severe damage in these genes underlies more subtle disorders of sexual development, such as disturbances in pubertal development and diminished fertility, is with few exceptions unknown. We are still aware of only a fraction of the information hidden in our genetic heritage. Developments in this field are nonetheless rapid, and molecular analyses will probably become more and more part and parcel of the workup of patients with a wide variety of disturbances in sexual development.

Genotyping is a valuable diagnostic complement to neonatal screening for congenital adrenal hyperplasia due to steroid 21-hydroxylase deficiency

To evaluate genotyping as a diagnostic complement to neonatal screening for congenital adrenal hyperplasia, 91 children who had been diagnosed with this condition between 1986 and 1997 were analyzed for mutations in the steroid 21-hydroxylase gene. Screening levels of 17-hydroxyprogesterone were compared in patients representing different genotypes. Genotyping was performed using allele-specific PCR, the patients were divided into four groups according to the severity of their mutations, and screening results were compared between these groups as well as with 141 values representing false positive samples. The screening levels of 17-hydroxyprogesterone were significantly different in the five groups of samples. Values above 500 nmol/L were clearly associated with the most severe genotypes, whereas conclusions concerning disease severity could not be drawn from individual samples representing lower levels. For example, values around 150-200 nmol/L could be seen in children with all degrees of disease severity and could also constitute false positive samples. We conclude that genotyping is a valuable diagnostic tool and a good complement to neonatal screening, especially in confirming or discarding the diagnosis in cases with slightly elevated 17-hydroxyprogesterone levels. An additional benefit is that it provides information on disease severity, which reduces the risk of overtreatment of mildly affected children.

Effects of missense mutations and deletions on membrane anchoring and enzyme function of human steroid 21-hydroxylase (P450c21)

We studied membrane binding and enzyme function of six variant forms of human steroid 21-hydroxylase (P450c21), a mutant (P30Q) from a patient with congenital adrenal hyperplasia, four artificial deletions in the amino terminal region (delS1 and del S2; the first and second hydrophobic segment, delS3; the region in between, delS4; the combination of these), and one naturally ocurring polymorphism in a region implicated to be critical for membrane integration (delL10). Enzyme function was assayed after transient expression in COS-1 cells, and membrane binding was studied by coupled in vitro transcription-translation in the presence of microsomal membranes. P450c21(delS1) retained some enzyme activity but showed severely reduced membrane binding. P450c21(P30Q), P450c21 (delS2), P450c21(delS3), and P450c21(delS4) had abolished enzyme function. P450c21(P30Q) and P450c21 (delS2) did not affect membrane binding, P450c21 (delS3) had slightly reduced binding with a qualitative difference suggested by the absence of a glycosylated form of the protein, and P450c21(delS4) had abolished membrane integration. No significant differences could be identified for the delL10 variant. These data support that P450c21 spans the membrane through its first hydrophobic domain only, and that the protein lacking this segment retains sufficiently normal structure to enable catalysis. They also confirm that P30Q is responsible for the severe phenotype of the patient in which it was found, and indicate that the common delL10 polymorphism does not have a major effect on enzyme function.

Failure of cortisone acetate treatment in congenital adrenal hyperplasia because of defective 11beta-hydroxysteroid dehydrogenase reductase activity

Congenital adrenal hyperplasia in children is often treated with cortisone acetate and fludrocortisone. It is known that certain patients with congenital adrenal hyperplasia require very high substitution doses of cortisone acetate, and a few patients do not respond to this treatment at all. A patient with 21-hydroxylase deficiency, for whom elevated pregnanetriol (P3) levels in urine were not suppressed during treatment with cortisone acetate (65 mg/m2 x day), was examined. The activation of cortisone to cortisol was assessed by measuring urinary metabolites of cortisone and cortisol. The patient's inability to respond to treatment with cortisone acetate was found to be caused by a low conversion of cortisone to cortisol, assumed to be secondary to low 11beta-hydroxysteroid dehydrogenase activity (11-oxoreductase deficiency). All exons and exon/intron junctions of the 11beta-hydroxysteroid dehydrogenase type1 gene (HSD11L) were sequenced without finding any mutations, but a genetic lesion in the promoter or other regulatory regions cannot be ruled out. The deficient 11-oxoreductase activity seems to have been congenital, in this case, but can possibly be attributable to a down-regulation of the enzyme activity. The results support the use of hydrocortisone, rather than cortisone acetate, for substitution therapy in adrenal insufficiency.

No overrepresentation of congenital adrenal hyperplasia in patients with adrenocortical tumours

OBJECTIVE

The development and progression of sporadic adrenocortical tumours are poorly understood. In autopsy studies adrenocortical tumours are found in between 2 and 9% of the general population. In congenital adrenal hyperplasia (CAH), decreased production of cortisol leads to increased secretion of ACTH from the pituitary, resulting in hyperplasia of the adrenals. More than 95% of all cases of CAH are due to steroid 21-hydroxylase deficiency, resulting from mutations in the CYP21 gene. In subjects homozygous and heterozygous for CYP21 mutations, adrenocortical tumours have been found in a high frequency compared to the general population, suggesting that chronic ACTH stimulation may play a role in the development of this tumour form. In order to test whether mild undiagnosed CAH is a common predisposing factor, we screened 27 patients with sporadic adrenocortical tumours for CYP21 mutations.

DESIGN

A retrospective study.

PATIENTS

We screened 27 patients with sporadic adrenocortical tumours, representing both benign and malignant as well as hormonally active and silent lesions.

MEASUREMENTS

Mutation analyses of the CYP21 gene was performed by allele-specific PCR on high molecular weight DNA. The method used detects the nine CYP21 mutations that are responsible for 95% of all disease-causing alleles in CAH.

RESULTS

No mutations were detected in any of the 23 DNA samples that were prepared from leucocytes. In 4 cases where no leucocyte DNA was available, tumour tissue was analysed. In one of these tumours, two CYP21 mutations, V281 L and L307insT, were found in heterozygous form.

CONCLUSION

Our data indicate that mild undiagnosed congenital adrenal hyperplasia is not a common underlying factor predisposing to adrenocortical tumours, at least not in the Swedish population.

A conformation-dependent epitope in Addison's disease and other endocrinological autoimmune diseases maps to a carboxyl-terminal functional domain of human steroid 21-hydroxylase

Idiopathic Addison's disease develops as a consequence of autoimmune destruction of steroid-producing cells in the adrenal gland. A major autoantigen is 21-hydroxylase (21OH; P450c21), which is involved in the biosynthesis of cortisol and aldosterone in the adrenal cortex. We selected a number of functionally important 21OH amino acid substitutions, found in patients with congenital adrenal hyperplasia, to study their effects on the binding of 21OH autoantibodies (21OHAb) to 21OH. The ability of 21OHAb to bind in vitro transcribed and translated wild-type 21OH and five different 21OH mutant proteins was quantified by liquid-phase assays. Sera from 21OHAb-positive patients with idiopathic Addison's disease (n = 24), Graves' disease (n = 3), and insulin-dependent diabetes mellitus (n = 1) were used. While the P105L, delE196, and G291S mutations had no effect on autoantibody binding, the P453S mutation had a considerable effect, and the R483P mutation almost completely abolished binding. Synthetic peptides corresponding to linear epitopes defined by amino acids 447-461 and 477-491 were unable to compete with wild-type 21OH for binding to autoantibodies. Direct 21OH DNA sequencing could not reveal any specific genetic variation in alleles found in 21OHAb-positive patients. We conclude that the region involving R483 plays a key role in the formation of a three-dimensional epitope in a functionally important C-terminal domain of the enzyme.

Long-term somatic follow-up of prenatally treated children with congenital adrenal hyperplasia

Prenatal virilization of female fetuses is a serious symptom associated with severe congenital adrenal hyperplasia. In attempt to avoid sexual ambiguity, prenatal treatment of 21-hydroxylase deficiency was initiated in 1984, with the first Scandinavian case treated in 1985. Here we have studied the outcome of prenatal diagnosis and therapy of 44 at-risk pregnancies monitored during the years 1985-1995 in Scandinavia. Treated mothers and children were compared with matched controls. Compared to their elder affected sisters, all 5 girls with severe congenital adrenal hyperplasia who were treated until term showed little virilization. Only 1 required surgery for labial fusion. The majority of the 44 dexamethasone-treated fetuses demonstrated normal pre- and postnatal growth compared to matched controls. However, several adverse events such as failure to thrive and delayed psychomotor development, were reported among the treated infants. In addition, treated mothers reported more side-effects during pregnancy than did controls. A significant increase in weight gain was observed during early pregnancy when treatment was initiated, but this initial rapid weight gain declined during late pregnancy or when treatment was terminated. Thus, experience to date suggests that prenatal treatment of affected female fetuses is generally efficient in minimizing virilization of external genitalia. However, there is still a need to collect more data concerning possible rare unfavorable effects of this therapy on mother and child.

Functional characterisation of mutations in the ligand-binding domain of the androgen receptor gene in patients with androgen insensitivity syndrome

Five mutations in the ligand-binding domain of the androgen receptor gene were identified in patients with complete (A765T, C784Y, R831X and M895T) or partial (R840G) androgen insensitivity. A765T and R831X have been reported previously whereas the other three mutations are novel. Receptors carrying these mutations were transiently expressed in COS-1 cells, and androgen binding and capacity to transactivate an androgen-responsive reporter gene were assayed. C784Y led to abolished androgen binding and transactivating capacity, R840G and M895T showed reduced specific binding and partial transactivation. The in vitro functions of the R840G and M895T mutants were improved with supraphysiological concentrations of steroid.

An update on the molecular genetics of congenital adrenal hyperplasia: diagnostic and therapeutic aspects

An update on the molecular genetics of congenital adrenal hyperplasia due to 21-hydroxylase deficiency is given. In Sweden, direct mutation detection has been used for genetic diagnosis of this disease since 1990. Around 400 affected 21-hydroxylase genes have been analyzed so far. Mutations that have arisen by interaction with the adjacent pseudogene, including gene deletion and nine smaller sequence aberrations, are responsible for the disease in around 95% of alleles. A total of 13 rare, mostly population-specific mutations have been characterized among the remaining 5%. Some of these rare mutations are present in the pseudogene at a low frequency, indicating that they have started to spread at a low rate in the population. The mutations can be divided into different groups according to severity. This makes it possible to predict clinical outcome in affected subjects based on genotyping. The risk of salt-wasting and prenatal virilization can be estimated, and overtreatment can be avoided in mildly affected cases.

Naturally occurring mutants of human steroid 21-hydroxylase (P450c21) pinpoint residues important for enzyme activity and stability

Three mutants (deletion of E196, G291S, and R483P) of steroid 21-hydroxylase (P450c21) from patients with inherited congenital adrenal hyperplasia had reduced activity toward progesterone and 17-hydroxyprogesterone after transient expression in cultured mammalian cells. In addition, both the E196 deletion and the R483P mutant had shorter half-lives than the wild-type enzyme, whereas the half-life of the G291S mutant was comparable with that of the normal protein. These results directly link the clinical situation with the three mutations and suggest that G291 is important for the catalytic activity of P450c21.

Molecular genetics of congenital adrenal hyperplasia (21-hydroxylase deficiency): implications for diagnosis, prognosis and treatment

The molecular genetics of congenital adrenal hyperplasia due to 21-hydroxylase deficiency are reviewed. In Sweden, mutation detection based on allele-specific PCR has been used for genetic diagnosis of this disease since 1993. Around 400 affected 21-hydroxylase genes have been analysed so far. An update of the spectrum of mutations among the Swedish patients shows that nine common pseudogene-derived mutations are responsible for the disease in around 95% of alleles. A total of 13 rare, mostly population-specific mutations have been characterized among the remaining 5%. The mutations can be divided into different groups according to severity. This makes it possible to predict clinical outcome in affected subjects based on genotyping. The risk of salt-wasting and prenatal virilization can be estimated, and over-treatment can be avoided in mildly affected cases.

[Prenatal diagnosis and treatment of adrenogenital syndrome. Prevent virilization of female fetuses]

Congenital adrenal hyperplasia (CAH) is the common name of a constellation of diseases that impair cortisol synthesis in the adrenal cortex. As defects in each of three steroidogenic enzymes, 21-hydroxylase, 11 beta-hydroxylase, and 3 beta-hydroxysteroid dehydrogenase, promote overproduction of adrenal androgens, affected female fetuses may be virilised. The major cause of CAH is 21-hydroxylase deficiency, the incidence of which is 1:10,000 live births in the Swedish population. Of the 10-15 children born in Sweden each year with 21-hydroxylase deficiency, 3-5 will be virilised girls who must undergo traumatic surgery of the external genitalia. This can be prevented by administration of dexamethasone to the gravida during pregnancy. Prenatal treatment was introduced in Sweden in 1985, prenatal diagnosis being based in most cases on direct mutational analysis using allele-specific PCR on DNA from chorionic villus samples. In our experience, genotype corresponds well to phenotype, and we recommend that all children with 21-hydroxylase deficiency be genotyped in order to prepare the family for rapid and reliable prenatal diagnosis and possible treatment when the next child is awaited. Since 1985, 35 women have received prenatal treatment in Sweden, six of the 35 fetuses being found to be affected females and treated until term. As compared with their older sisters, all of these six girls were characterised by no signs, or only minor signs, of virilisation, and only one required surgery because of labial fusion and recurrent urinary tract infections. As a group, the 35 infants were characterised by normal birth weight and length, and normal growth during the first year of life. Passage of developmental milestones was normal though several adverse events, both in treated mothers and infants, have been reported. Approximately one fourth of the women treated throughout pregnancy reported some side-effect (e.g., excessive weight gain, severe cutaneous striae, mood fluctuations and irritability, acne and hirsutism, or oedema). One unaffected boy, treated for seven weeks, was born with severe hydrocephalus and agenesis of the corpus callosum; two affected sisters and one unaffected girl were characterised by failure to thrive during the first year of life, but later recovered (one of the affected sisters was later diagnosed as suffering from mitochondrial disease). Although in our experience prenatal treatment with dexamethasone is effective in preventing virilisation of girls with 21-hydroxylase deficiency, some adverse events have been noted in treated infants. As it remains unknown whether these events were attributable to the treatment, it must still be regarded as experimental, and its use should be centralised and meticulously monitored until more experience has been gained.

Prophylactic adrenalectomy of a three-year-old girl with congenital adrenal hyperplasia: pre- and postoperative studies

Long term follow-up studies of children with congenital adrenal hyperplasia have documented less than desirable outcomes, including reduction in final adult height, obesity, virilism, and decreased fertility. We have proposed that children with the most severe forms of congenital adrenal hyperplasia would be better off if their adrenals were removed at an early age. We report here on our experience with prophylactic bilateral adrenalectomy in a 3-yr-old girl with a double null mutation of the CYP21 gene. The results of sodium balance studies, performed preoperatively on our patient and her unaffected fraternal twin sister, and hormonal data are presented as well. In contrast to her twin, who markedly increased her sodium retention in response to ACTH, our patient showed increased natriuresis, suggesting a deleterious effect of her adrenals on sodium homeostasis. Adrenalectomy was carried out at the time of necessary genital repair. No surgical or postsurgical complications were encountered.

A cluster of missense mutations at Arg356 of human steroid 21-hydroxylase may impair redox partner interaction

Lesions in the gene encoding steroid 21-hydroxylase result in congenital adrenal hyperplasia, with impaired secretion of cortisol and aldosterone from the adrenal cortex and overproduction of androgens. A limited number of mutations account for the majority of mutated alleles, but additional rare mutations are responsible for the symptoms in some patients. A total of 11 missense mutations has previously been implicated in this enzyme deficiency. We describe two novel missense mutations, both affecting the same amino acid residue, Arg356. The two mutations, R356P and R356Q, were reconstructed by in vitro site-directed mutagenesis, the proteins were transiently expressed in COS-1 cells, and enzyme activity towards the two natural substrates, 17-hydroxyprogesterone and progesterone, was determined. The R356P mutant reduced enzyme activity to 0.15% towards both substrates, whereas the R356Q mutant exhibited 0.65% of normal activity towards 17-hydroxyprogesterone, and 1.1% of normal activity towards progesterone. These activities correspond to the degrees of disease manifestation of the patients in whom they were found. Arg356 is located in a region which recently has been implicated in redox partner interaction, by modelling the structure of two other members of the cytochrome P450 superfamily. Of the 11 previously described missense mutations, three affect arginine residues within this protein domain. With the addition of R356P and R356Q, there is a clear clustering of five mutations to three closely located basic amino acids. This supports the model in which this protein domain is involved in redox partner interaction, which takes places through electrostatic interactions between charged amino acid residues.

Synergistic effect of partially inactivating mutations in steroid 21-hydroxylase deficiency

Lesions in the gene encoding steroid 21-hydroxylase result in congenital adrenal hyperplasia, with impaired secretion of cortisol and aldosterone from the adrenal cortex and overproduction of androgens. Mild forms of the disease cause late-onset symptoms of hyperandrogenism and are thought to be largely underdiagnosed. A limited number of mutations account for the majority of mutated alleles, but additional rare mutations are responsible for the symptoms in some patients. We previously reported a rare allele in two siblings with late-onset disease. This allele contained three sequence alterations, a C to T transition 4 bases upstream of translation initiation, a CCG to CTG change at codon 105 (P105L), and a CCC to TCC transition at codon 453 (P453S). The latter mutation has been found in other ethnic groups, whereas P105L seems to be unique to this family. We have now analyzed the functional consequences of the -4, P105L, and P453S sequence alterations by in vitro translation and after expression of mutant enzyme in cultured cells. As expected, the base substitution at position-4 had no measurable effect on gene expression. The P105L mutation reduced enzyme activity to 62% for 17-hydroxyprogesterone and 64% for progesterone, and the P453S mutation reduced activity to 68% and 46%, respectively. When present in combination, the two mutations caused a reduction of enzyme activity to 10% for 17-hydroxyprogesterone and 7% for progesterone. These results indicate that P105L and P453S can be expected to result in a very subtle disease manifestation when not found in combination, motivating their inclusion when genotyping to ascertain undiagnosed patients with the mildest forms of 21-hydroxylase deficiency.

An intron 1 splice mutation and a nonsense mutation (W23X) in CYP21 causing severe congenital adrenal hyperplasia

Direct DNA sequencing of the steroid 21-hydroxylase gene (CYP21) revealed two novel mutations in two patients with severe congenital adrenal hyperplasia. The nonsense mutation Trp23Stop (TGG --> TGA) was found in a woman with the simple virilizing form of the disease. She was a compound heterozygote, with the previously described Ile173Asn mutation on her other allele. A boy, who developed salt-wasting in the neonatal period, carried an allele with a novel mutation of the canonical splice acceptor site in intron 1 (AG --> GG). He was also a compound heterozygote, with the well-known splice mutation in intron 2 on his other allele.

Molecular approaches for the diagnosis of 21-hydroxylase deficiency and congenital adrenal hyperplasia

Congenital adrenal hyperplasia due to 21-hydroxylase deficiency results in deficiency of cortisol and aldosterone and overproduction of androgens. The 21-hydroxylase locus has a complicated structure, with a highly homologous pseudogene (CYP21P) and an active gene (CYP21) in tandem repeats, a high degree of interindividual variation in gene copy numbers, and exchange of sequences between CYP21P and CYP21. Nine mutations, representing sequences that are normally present in the pseudogene, account for about 95% of all affected CYP21 alleles. Accurate and rapid diagnostic evaluation of congenital adrenal hyperplasia due to 21-hydroxylase deficiency can be performed by typing directly for disease-causing mutations using allele-specific polymerase chain reaction (PCR). A strong correlation exists between genotype and phenotype; mutational analysis can be used to predict disease severity in affected individuals.

Early growth is not increased in untreated moderately severe 21-hydroxylase deficiency

The pretreatment growth of 1 British and 14 Swedish children with late (2-7 years) diagnosis of 21-hydroxylase deficiency (21OHD) was studied. The latter group included all patients diagnosed in Sweden after 1986. Twelve had mutations of the 21-hydroxylase gene that are generally associated with moderately severe ("simple virilizing") forms of 21OHD, one had a severe ("salt-losing") and one a mild ("non-classical") form. The British girl was followed from 4 months of age. She had grossly elevated levels of 17 alpha-hydroxyprogesterone, androstenedione and testosterone in blood, but her parents refused treatment until she was 4 years of age. None of the 15 children showed any significant increase in growth or progress of virilization until after 18 months of age. These observations indicate that growth during the first 1.5 years is not very sensitive to androgens. Thus glucocorticoid replacement during the first year of life should be kept to a minimum to avoid over-treatment.

Characterization of mutations on the rare duplicated C4/CYP21 haplotype in steroid 21-hydroxylase deficiency

We have defined the mutations causing congenital adrenal hyperplasia in three Swedish patients carrying a rare haplotype containing two mutated steroid 21-hydroxylase genes (CYP21) in addition to one pseudogene (CYP21P). The presence of such haplotypes complicates genetic diagnosis and screening of mutations in 21-hydroxylase deficiency, and we show how these genotypes can be resolved by amplification and analysis of each gene separately. In all cases, the rare haplotype carried the same combination of disease-causing mutations; one of the genes had the splice mutation at base 659 in intron 2, and the other had the nonsense mutation at base 1999 in exon 8 (CAG to TAG). We have thus characterized the most common haplotype containing duplicated CYP21 genes. The frequency of this haplotype is low, and if additional such haplotypes are present, they are rare in this population.

Mutational spectrum of the steroid 21-hydroxylase gene in Sweden: implications for genetic diagnosis and association with disease manifestation

We have characterized the disease-causing mutations in the steroid 21-hydroxylase genes of 127 patients with different clinical forms of congenital adrenal hyperplasia, representing 186 unrelated chromosomes. The gene was completely absent on 29.8% of the chromosomes, and this together with the I2 splice (27.7%), I173N (20.8%), V282L (5.4%), and R357W (3.8%) mutations constitute 87.5% of all affected chromosomes. In total, 15 different sequence aberrations combine to form 19 different disease-causing alleles. The results confirm that genotyping is an efficient means of diagnosing steroid 21-hydroxylase deficiency, although special consideration is needed to resolve genotypes when full families are not available. Clinical presentations of the different combinations of mutations indicate that genotyping is reliable for prediction of clinical outcome in patients with 21-hydroxylase deficiency. It is especially helpful in determining whether in utero treatment of affected females is indicated and in classifying the severity of 21-hydroxylase deficiency in children diagnosed through neonatal screening, before symptoms have appeared.

Regulation of human insulin receptor RNA splicing in vivo

Alternative splicing involving the inclusion or exclusion of exon 11 in insulin receptor mRNA results in two isoforms of the alpha subunit. The two subunits display tissue-specific variation in relative abundance at both RNA and protein levels and discrete differences in biological properties. We have previously reported a small decrease in the relative level of RNA molecules lacking exon 11 (Ex 11-) in skeletal muscle of non-insulin-dependent diabetes mellitus (NIDDM) patients. In the present study, we describe a drastically altered ratio in favor of Ex 11- RNA in a NIDDM patient with markedly impaired insulin-mediated glucose utilization. The ratio between the splice variants changed from 74% to 48% Ex 11- RNA after initiation of insulin treatment, which considerably improved his blood glucose concentrations and insulin-stimulated glucose utilization rate. This shows that splicing can be regulated by metabolic and/or hormonal factors in response to changes in the in vivo milieu. No genomic deletion or base substitution in either the coding regions or exon-intron borders was found that explains the altered splicing. Heterozygous mutations were excluded in sequences of putative importance for splicing outside the analyzed regions as both alleles were expressed and spliced in an identical fashion. Furthermore, these results suggest that this patient fails to regulate alternative splicing of exon 11 in the manner observed in most NIDDM patients and that this defect is associated with the extreme impairment in insulin action.

A steroid 21-hydroxylase allele concomitantly carrying four disease-causing mutations is not uncommon in the swedish population

We describe a steroid 21-hydroxylase allele carrying four disease-causing mutations, viz. I173N, V282L, I237N + V238E + M240K, and the insertion of T at 308 L. The first two are established causes of partial enzyme deficiency, whereas the last two are known to result in the most severe, salt-wasting form of the disease. All four mutations are normally found in the pseudogene. This abnormal allele was found in the general Swedish population (6 out of 354 individuals), but has so far not been identified among 21-hydroxylase deficiency patients. The existence of alleles with multiple mutations illustrates the importance of segregating mutations for the correct genetic diagnosis of steroid 21-hydroxylase deficiency; an allele-specific polymerase chain reaction can be successfully employed for this purpose when families are unavailable.

Two new mutations in the porphobilinogen deaminase gene and a screening method using PCR amplification of specific alleles

Acute intermittent porphyria (AIP) is attributable to defects in the porphobilinogen deaminase (PBGD) gene. Two new mutations have been found in the PBGD gene in Swedish families. The first is a G to A splice mutation in the last position of intron 9. A screening method using allele-specific amplification has been designed for the rapid detection of this mutation. The second mutation is a C to T substitution in exon 10, changing Arg201 to Trp. This mutation can be detected by restriction enzyme cleavage.