5alpha-reductase type 2 mutations are present in some boys with isolated hypospadias

The Molecular Basis of 5α-Reductase Type 2 Deficiency

The 5α-reductase type 2 enzyme catalyzes the conversion of testosterone into dihydrotestosterone, playing a crucial role in male development. This enzyme is encoded by the SRD5A2 gene, which maps to chromosome 2 (2p23), consists of 5 exons and 4 introns, and encodes a 254 amino acid protein. Disruptions in this gene are the molecular etiology of a subgroup of differences of sex development (DSD) in 46,XY patients. Affected individuals present a large range of external genitalia undervirilization, ranging from almost typically female external genitalia to predominantly typically male external genitalia with minimal undervirilization, including isolated micropenis. This is an updated review of the implication of the SRD5A2 gene in 5α-reductase type 2 enzyme deficiency. For that, we identified 451 cases from 48 countries of this particular 46,XY DSD from the literature with reported variants in the SRD5A2 gene. Herein, we present the SRD5A2 mutational profile, the SRD5A2 polymorphisms, and the functional studies related to SRD5A2 variants to detail the molecular etiology of this condition.

New frontiers on the molecular underpinnings of hypospadias according to severity

Hypospadias, which is characterised by the displacement of the urethral meatus from its typical anatomical location in males, shows various degrees of severity. In this systematic review, we surveyed our current understanding of the genetics of isolated hypospadias in humans according to the severity of the condition. We found that sequencing and genotyping approaches were the preferred methods of study and that single nucleotide polymorphisms were the most common finding associated with hypospadias. Most genes fell into four gene-pathway categories related to androgens, oestrogens, growth factors, or transcription factors. Few hypospadias studies classify their findings by severity. Taken together, we argue that it is advantageous to take into consideration the severity of the condition in search of novel candidates in the aetiology of hypospadias. Abbreviations: AR: androgen receptor; ATF3: activating transcription factor 3; BMP4: bone morphogenetic protein 4; BMP7: bone morphogenetic protein 7; CYP17: steroid 17-alpha-hydroxylase/17,20 lyase; CYP1A1: cytochrome P450 1A1; CYP3A4: cytochrome P450 3A4; CNVs: copy number variants; DGKK: diacylglycerol kinase kappa; ESR1: oestrogen receptor 1; ESR2: oestrogen receptor 2; FGF8: fibroblast growth factor 8; FGF10: fibroblast growth factor 10; FGFR2: fibroblast growth factor receptor 2; HOXA4: homeobox protein Hox-A4; HOXB6: homeobox protein Hox-B6; HSD17B3: hydroxysteroid 17-beta dehydrogenase 3; MAMLD1: mastermind-like domain-containing protein 1; SF-1: splicing factor 1; SHH: sonic hedgehog; SNPs: single nucleotide polymorphisms; SOX9: SRY-box 9; SRD5A2: steroid 5 alpha-reductase 2; SRY: sex-determining region Y protein; STAR: steroidogenic acute regulatory protein; STARD3: StAR-related lipid transfer protein 3; STS: steryl-sulfatase; WT1: Wilms tumour protein; ZEB1: zinc finger oestrogen-box binding homeobox 1.

Integrative and Analytical Review of the 5-Alpha-Reductase Type 2 Deficiency Worldwide

Introduction

The conversion of testosterone into dihydrotestosterone is catalyzed by the 5α-reductase type 2 enzyme which plays a crucial role in the external genitalia virilization. It is encoded by the SRD5A2 gene. Allelic variants in this gene cause a 46,XY DSD with no genotype-phenotype relationship. It was firstly reported in the early 70s from isolated clusters. Since then, several cases have been reported. Putting together, it will expand the knowledge on the molecular bases of androgen milieu.

Methods

We searched for SRD5A2 allelic variants (AV) in the literature (PubMed, Embase, MEDLINE) and websites (ensembl, HGMD, ClinVar). Only cases with AV in both alleles, either in homozygous or compound heterozygous were included. The included cases were analyzed according to ethnicity, exon, domain, aminoacid (aa) conservation, age at diagnosis, sex assignment, gender reassignment, external genitalia virilization and functional studies. External genitalia virilization was scored using Sinnecker scale. Conservation analysis was carried out using the CONSURF platform. For categorical variables, we used X2 test and Cramer's V. Continuous variables were analyzed by t test or ANOVA. Concordance was estimated by Kappa.

Results

We identified 434 cases of 5ARD2 deficiencies from 44 countries. Most came from Turkey (23%), China (17%), Italy (9%), and Brazil (7%). Sixty-nine percent were assigned as female. There were 70% of homozygous allelic variants and 30% compound heterozygous. Most were missense variants (76%). However, small indels (11%), splicing (5%) and large deletions (4%) were all reported. They were distributed along with all exons with exon 1 (33%) and exon 4 (25%) predominance. Allelic variants in the exon 4 (NADPH-binding domain) resulted in lower virilization (p<0.0001). The codons 55, 65, 196, 235 and 246 are hotspots making up 25% of all allelic variants. Most of them (76%) were located at conserved aa. However, allelic variants at non-conserved aa were more frequently indels (28% vs 6%; p<0.01). The overall rate of gender change from female to male ranged from 16% to 70%. The lowest rate of gender change from female to male occurred in Turkey and the highest in Brazil. External genitalia virilization was similar between those who changed and those who kept their assigned gender. The gender change rate was significantly different across the countries (V=0.44; p<0.001) even with similar virilization scores.

Conclusion

5ARD2 deficiency has a worldwide distribution. Allelic variants at the NADPH-ligand region cause lower virilization. Genitalia virilization influenced sex assignment but not gender change which was influenced by cultural aspects across the countries. Molecular diagnosis influenced on sex assignment, favoring male sex assignment in newborns with 5α-reductase type 2 deficiency.

Novel Genotype in Two Siblings with 5-α-reductase 2 Deficiency: Different Clinical Course due to the Time of Diagnosis

Steroid 5-α-reductase-2 (5-ARD) deficiency is a result of mutations of the SRD5A2 gene. It causes the disorder of sexual differentiation (DSD) in 46,XY individuals with a variable genital phenotype. We present two siblings with female external genitalia at birth and bilateral inguinal testes, raised as females. These are the first molecularly characterized patients from the Republic of North Macedonia (RN Macedonia) with a different clinical course due to the time of the diagnosis. Diagnosis of Patient 1 was based upon the detection of bilateral inguinal testes and testosterone/dihidrotestosterone ratio. Sex reversal was initiated by testes removal at the age of 20 months. Breast implantation and vaginoplasty were performed in adolescence and the girl is comfortable with the female sex. Her sibling, Patient 2, raised as a girl, was clinically assessed at 11.5 years due to the growth of phalus, deep voice and Adam's apple enlargement. No change of gender was accepted. Complex molecular analysis including multiplex quantitative fluorescent polymerase chain reaction (PCR) screening for sex chromosome aneuploidies and SRY presence, Sanger sequencing combined with multiplex ligation-dependent probe amplification (MLPA), microarray-based comparative genomic hybridization (aCGH), and real-time PCR analysis for detection of exon copy number changes confirmed a novel c.146C>A (p.Ala49Asp) point mutation in the first exon inherited from the mother, and complete deletion of the first exon and adjacent regions inherited from the father. Novel genotype causing 5-ARD is presented. Genetic analysis is useful for the diagnosis and timely gender assignment in patients with 5-ARD. However, final gender assignment is difficult and requires combined medical interventions.

Growth Pattern in Chinese Children With 5α-Reductase Type 2 Deficiency: A Retrospective Multicenter Study

BACKGROUND

5α-reductase type 2 deficiency (5αRD) is an autosomal recessive hereditary disease of the group of 46, XY disorders of sex development (DSD).

OBJECTIVE

To study the growth pattern in Chinese pediatric patients with 5αRD.

SUBJECTS

Data were obtained from 141 patients with 5αRD (age: 0-16 years old) who visited eight pediatric endocrine centers from January 2010 to December 2017.

METHODS

In this retrospective cohort study, height, weight, and other relevant data were collected from the multicenter hospital registration database. Baseline luteinizing hormone (LH), follicle stimulating hormone (FSH), testosterone (T), and dihydrotestosterone (DHT) after human chorionic gonadotropin (HCG) stimulation test were measured by enzyme enhanced chemiluminescence assay. Bone age (BA) was assessed using the Greulich-Pyle (G-P) atlas. Growth curve was constructed based on λ-median-coefficient of variation method (LMS).

RESULTS

The height standard deviation scores (HtSDS) and weight standard deviation scores (WtSDS) in 5αRD children were in the normal range as compared to normal boys. Significantly higher HtSDS was observed in patients with 5αRD who were <1 year old (t = 3.658, 2.103, P = 0.002, 0.048, respectively), and higher WtSDS in those <6 months old (t = 2.756, P = 0.012). Then HtSDS and WtSDS decreased gradually and fluctuated near the median of the same age until 13 years. WtSDS in 5αRD children from northern China were significantly higher than those from the south (Z = -2.670, P = 0.008). The variation tendency of HtSDS in Chinese 5αRDs was consistent with the trend of stimulating T. HtSDS and stimulating T in the external masculinization score (EMS) <7 group were slightly higher than those in EMS ≥ 7 group without significant difference. Additionally, the ratio of BA over chronological age (BA/CA) was significantly <1 in children with 5αRD.

CONCLUSION

Children with 5αRD had a special growth pattern that was affected by high levels of T, while DHT played a very small role in it. Their growth accelerated at age <1 year, followed by slowing growth and fluctuating height near normal median boys' height. The BA was delayed in 5αRD children. Androgen treatment, which may be considered anyway for male 5αRD patients with a micropenis, may also be beneficial for growth.

Gene changes may minimize masculinizing and defeminizing influences of exposure to male cotwins in female callitrichine primates

BACKGROUND

Sexual differentiation in female mammals can be altered by the proximity of male littermates in utero, a phenomenon known as the intrauterine position effect (IUP). Among simian primates, callitrichines (marmosets and tamarins) are likely candidates for IUP, since they exhibit obligate dizygotic twinning and fetuses share extensive vascularization in utero. In this paper, we determined whether female reproductive parameters are altered by gestating with a male twin and evaluated changes in genes associated with anti-Müllerian and steroid hormones in twinning callitrichine primates.

METHODS

We assessed the impact of gestation with male cotwins on reproductive performance and survivorship in female marmosets (Callithrix) and lion tamarins (Leontopithecus), contrasting measures for females gestated with one or more littermates (M+) or no male littermates (0M). We compared targeted coding regions for genes involved in steroidal and anti-Müllerian hormone mediation of sexual differentiation for representatives of twinning callitrichines (Callithrix, Saguinus, and Leontopithecus) with closely related New World primates that produce single births (Saimiri and Callimico).

RESULTS

IUP effects in females were absent in female callitrichine primates: age at first ovulation, average litter size, and the proportion of stillborn infants, and lifetime survivorship did not differ between M+ and 0M females. We documented multiple nonsynonymous substitutions in genes associated with steroid synthesis, transport, and cellular action (SRD5A2, CYP19A1, SHBG, and AR) and with anti-Müllerian hormone (AMH and AMHR2) in callitrichines. In the only callitrichine to produce single infants (Callimico), two genes contained nonsynonymous substitutions relative to twinning callitrichines (CYP19A1 and AMRHR2); these substitutions were identical with nontwinning Saimiri and humans, suggesting a reversion to an ancestral sequence.

CONCLUSIONS

In spite of a shared placental vasculature with opposite-sex twins throughout embryonic and fetal development, female callitrichine primates gestated with a male cotwin exhibit no decrement in reproductive performance relative to females gestated with female cotwins. Hence, IUP effects on female reproduction in callitrichines are modest. We have identified mutations in candidate genes relevant for steroid hormone signaling and metabolism, and especially in AMH-related genes, that are likely to alter protein structure and function in the callitrichines. These mutations may confer protection for females from the masculinizing and defeminizing influences of gestating with a male cotwin.

Association between SNP12 in estrogen receptor α gene and hypospadias: a systematic review and meta-analysis

To investigate the association between single nucleotide polymorphism 12 in estrogen receptor α gene and hypospadias, four databases (PubMed, Web of Science, Embase and Cochrane Library) were electronically searched by 2nd November 2015. Finally, four studies were included for our meta-analysis, involving 1379 cases and 1648 controls. A quality assessment was performed using the Newcastle–Ottawa Scale of case–control study. Meta-analysis and publication bias measuring were all done by Stata 12.0. No significant publication bias (P_Begg = 0.296, P_Egger = 0.161) was found. Overall, there was statistically significant association for recessive genetic model (AA vs. GA + GG: OR 3.45, 95 % CI [1.89, 6.30], P = 0.038). Moreover, the positive result was confirmed using trial sequential analysis even only three original studies. For allele model, there was also statistically significant association (allele A vs. G: OR 1.43, 95 % CI [1.23, 1.67], P = 0.034). Meanwhile, A allele as a risk factor turned out to be true positive by trial sequential analysis. In a word, this meta-analysis suggested that the single nucleotide polymorphism 12 definitely increase the risk of hypospadias.

The Genetic and Environmental Factors Underlying Hypospadias

Hypospadias results from a failure of urethral closure in the male phallus and affects 1 in 200-300 boys. It is thought to be due to a combination of genetic and environmental factors. The development of the penis progresses in 2 stages: an initial hormone-independent phase and a secondary hormone-dependent phase. Here, we review the molecular pathways that contribute to each of these stages, drawing on studies from both human and mouse models. Hypospadias can occur when normal development of the phallus is disrupted, and we provide evidence that mutations in genes underlying this developmental process are causative. Finally, we discuss the environmental factors that may contribute to hypospadias and their potential immediate and transgenerational epigenetic impacts.

A49T, R227Q and TA repeat polymorphism of steroid 5 alpha-reductase type II gene and Hypospadias risk in North Indian children

Background/Aims

Hypospadias is a common congenital error of genital development, the frequency of which is increasing. As androgens have a significant role in the development of the male urethra, we sought to investigate the association between functional polymorphisms of SRD5A2 gene in relation to hypospadias.

Methods

We examined DNA samples of 96 cases and 105 controls for SRD5A2-A49T, R227Q and TA repeat gene polymorphisms.

Result

Absence of 49T locus and 227Q locus was observed in the present study. At the (TA) n repeat site, TA (0) allele was observed to be the most common allele in both cases (91.7%) and controls (90%). TA (9/9) genotype exhibited an odds ratio of 3.03 (95% C.I. = 0.18–50.14, p = 0) with respect to only middle phenotypes. Analysis of the demographic data depicted the agricultural background aspect of the parents of the cases. 72.27% of the cases (affected with Hypospadias) have parents having agriculture as a primary occupation.

Conclusion

As longer TA repeats are associated with lower enzymatic activity and lower DHT levels as reported among Caucasians, this polymorphism may have an effect (rather small) in predisposing the population of the present study to the risk of Hypospadias of lesser severity. Due to small sample size, the 3.03 O.R. is not significant and a larger sample is needed to validate the results.

Large scale screening of Hypospadias and other 46 X,Y disorders of sexual development is needed especially in India, where the majority of the population is from agricultural background. The results of the present study are likely to assist the health planners to initiate screening of Hypospadias among the farmer community to combat the risk of Hypospadias.

Intrauterine growth restriction and hypospadias: is there a connection?

Hypospadias is one of the most common congenital malformations of the genitourinary tract in males. It is an incomplete fusion of urethral folds early in fetal development and may be associated with other malformations of the genital tract. The etiology is poorly understood and may be hormonal, genetic, or environmental, but most often is idiopathic or multifactorial. Among many possible risk factors identified, of particular importance is low birth weight, which is defined in various ways in the literature. No mechanism has been identified for the association of low birth weight and hypospadias, but some authors propose placental insufficiency as a common inciting factor. Currently, there is no standardized approach for evaluating children with hypospadias in the setting of intrauterine growth restriction. We reviewed the available published literature on the association of hypospadias and growth restriction to determine whether it should be considered a separate entity within the category of disorders of sexual differentiation.

46,XY disorder of sexual development resulting from a novel monoallelic mutation (p.Ser31Phe) in the steroid 5α-reductase type-2 (SRD5A2) gene

Inactivating mutations of the 5α-steroid reductase type-2 (SRD5A2) gene result in a broad spectrum of masculinization defects, ranging from a male phenotype with hypospadias to a female phenotype with Wolffian structures. Molecular studies of the SRD5A2 revealed a new heterozygous gene variant within the coding region that results in phenotypic expression. A c.92C>T transition changing serine to phenylalanine at codon 31 of exon 1 (p.Ser31Phe) was identified in a patient with 46,XY disorder of sexual development who displayed glandular hypospadias with micropenis and bilateral cryptorchidism. The restoration of the p.Ser31Phe mutation by site-directed mutagenesis and transient expression assays using cultured HEK-293 cells showed that this novel substitution does not abolish but does deregulate the catalytic efficiency of the enzyme. Thus, the maximum velocity (V_max) value was higher for the mutant enzyme (22.5 ± 6.9 nmol DHT mg protein⁻¹ h⁻¹) than for the wild-type enzyme (9.8 ± 2.0 nmol DHT mg protein⁻¹ h⁻¹). Increased in vitro activity of the p.Ser31Phe mutant suggested an activating effect. This case provides evidence that heterozygous missense mutations in SRD5A2 may induce the abnormal development of male external genitalia.

Coordinated activity of Spry1 and Spry2 is required for normal development of the external genitalia

Development of the mammalian external genitalia is controlled by a network of signaling molecules and transcription factors. Because FGF signaling plays a central role in this complicated morphogenetic process, we investigated the role of Sprouty genes, which are important intracellular modulators of FGF signaling, during embryonic development of the external genitalia in mice. We found that Sprouty genes are expressed by the urethral epithelium during embryogenesis, and that they have a critical function during urethral canalization and fusion. Development of the genital tubercle (GT), the anlage of the prepuce and glans penis in males and glans clitoris in females, was severely affected in male embryos carrying null alleles of both Spry1 and Spry2. In Spry1(-/-);Spry2(-/-) embryos, the internal tubular urethra was absent, and urothelial morphology and organization was abnormal. These effects were due, in part, to elevated levels of epithelial cell proliferation in Spry1(-/-);Spry2(-/-) embryos. Despite changes in overall organization, terminal differentiation of the urothelium was not significantly affected. Characterization of the molecular pathways that regulate normal GT development confirmed that deletion of Sprouty genes leads to elevated FGF signaling, whereas levels of signaling in other cascades were largely preserved. Together, these results show that levels of FGF signaling must be tightly regulated during embryonic development of the external genitalia in mice, and that this regulation is mediated in part through the activity of Sprouty gene products.

Minor hypospadias: the "tip of the iceberg" of the partial androgen insensitivity syndrome

BACKGROUND

Androgens are critical in male external genital development. Alterations in the androgen sensitivity pathway have been identified in severely undermasculinized boys, and mutations of the androgen receptor gene (AR) are usually found in partial or complete androgen insensitivity syndrome (AIS).

OBJECTIVE

The aim of this study was to determine whether even the most minor forms of isolated hypospadias are associated with AR mutations and thus whether all types of hypospadias warrant molecular analysis of the AR.

MATERIALS AND METHODS

Two hundred and ninety-two Caucasian children presenting with isolated hypospadias without micropenis or cryptorchidism and 345 controls were included prospectively. Mutational analysis of the AR through direct sequencing (exons 1-8) was performed. In silico and luciferase functional assays were performed for unreported variants.

RESULTS

Five missense mutations of the AR were identified in 9 patients with glandular or penile anterior (n = 5), penile midshaft (n = 2) and penile posterior (n = 2) hypospadias, i.e., 3%: p.Q58L (c.173A>T), 4 cases of p.P392S (c.1174C>T), 2 cases of p.A475V (c.1424C>T), p.D551H (c.1651G>C) and p.Q799E (c.2395C>G). None of these mutations was present in the control group. One mutation has never been reported to date (p.D551H). It was predicted to be damaging based on 6 in silico models, and in vitro functional studies confirmed the lowered transactivation function of the mutated protein. Three mutations have never been reported in patients with genital malformation but only in isolated infertility: p.Q58L, p.P392S, and p.A475V. It is notable that micropenis, a cardinal sign of AIS, was not present in any patient.

CONCLUSION

AR mutations may play a role in the cause of isolated hypospadias, even in the most minor forms. Identification of this underlying genetic alteration may be important for proper diagnosis and longer follow-up is necessary to find out if the mutations cause differences in sexual function and fertility later in life.

Environmental and genetic contributors to hypospadias: a review of the epidemiologic evidence

This review evaluates current knowledge related to trends in the prevalence of hypospadias, the association of hypospadias with endocrine-disrupting exposures, and the potential contribution of genetic susceptibility to its etiology. The review focuses on epidemiologic evidence. Increasing prevalence of hypospadias has been observed, but such increases tend to be localized to specific regions or time periods. Thus, generalized statements that hypospadias is increasing are unsupported. Owing to the limitations of study designs and inconsistent results, firm conclusions cannot be made regarding the association of endocrine-disrupting exposures with hypospadias. Studies with more rigorous study designs (e.g., larger and more detailed phenotypes) and exposure assessment that encompasses more breadth and depth (e.g., specific endocrine-related chemicals) will be critical to make better inferences about these important environmental exposures. Many candidate genes for hypospadias have been identified, but few of them have been examined to an extent that enables solid conclusions. Further study is needed that includes larger sample sizes, comparison groups that are more representative of the populations from which the cases were derived, phenotype-specific analyses, and more extensive exploration of variants. In conclusion, examining the associations of environmental and genetic factors with hypospadias remain important areas of inquiry, although our actual understanding of their contribution to hypospadias risk in humans is currently limited.

Targeting 5α-reductase for prostate cancer prevention and treatment

Testosterone is the most abundant circulating androgen, and can be converted to dihydrotestosterone (DHT), a more potent androgen, by the 5α-reductase enzymes in target tissues. Current treatments for prostate cancer consist of reducing androgen levels by chemical or surgical castration or pure antiandrogen therapy that directly targets the androgen receptor (AR). Although these therapies reduce tumor burden and AR activity, the cancer inevitably recurs within 18-30 months. An approach targeting the androgen-AR axis at different levels could, therefore, improve the efficacy of prostate cancer therapy. Inhibition of 5α-reductase is one such approach; however, the two largest trials to investigate the use of the 5α-reductase inhibitors (5ARIs) finasteride and dutasteride in patients with prostate cancer have shown that, although the incidence of cancer was reduced by 5ARI treatment, those cancers that were detected were more aggressive than in patients treated with placebo. Thus, the best practice for using these drugs to prevent and treat prostate cancer remains unclear.

ZEB1 is estrogen responsive in vitro in human foreskin cells and is over expressed in penile skin in patients with severe hypospadias

PURPOSE

We determined the effect of estrogen on ZEB1 in vitro and tested the hypothesis that ZEB1 is over expressed in the penile skin of subjects with hypospadias.

MATERIALS AND METHODS

Hs68 cells, a fibroblast cell line derived from human foreskin, were exposed to 0, 1, 10 and 100 nM estrogen, and the expression level of ZEB1 was assessed using reverse transcription real-time polymerase chain reaction, Western blot and immunocytochemical analysis. Next, preputial skin was prospectively collected from case and control subjects at hypospadias repair (37 cases) and circumcision (11). Hypospadias was classified as severe (13 cases) or mild (24) based on the position of the urethral meatus. ZEB1 expression was quantified using reverse transcription real-time polymerase chain reaction, Western blot and immunohistochemical analysis.

RESULTS

Estrogen increased ZEB1 expression at the mRNA and protein levels in Hs68 cells in a concentration dependent fashion (p <0.01). Subjects with severe hypospadias had significantly higher ZEB1 mRNA levels and protein expression compared to controls or subjects with mild hypospadias (both p <0.01). Subjects with severe hypospadias had increased expression of ZEB1 in the basal layers of the preputial epidermis.

CONCLUSIONS

Estrogen increases ZEB1 expression in a human foreskin fibroblast cell line in vitro. Furthermore, ZEB1 is significantly over expressed in the penile skin of subjects with severe hypospadias. We propose that ZEB1 overexpression may contribute to development of hypospadias and may mediate the effect of estrogen on developing external male genitalia.

Human balanced translocation and mouse gene inactivation implicate Basonuclin 2 in distal urethral development

We studied a man with distal hypospadias, partial anomalous pulmonary venous return, mild limb-length inequality and a balanced translocation involving chromosomes 9 and 13. To gain insight into the etiology of his birth defects, we mapped the translocation breakpoints by high-resolution comparative genomic hybridization (CGH), using chromosome 9- and 13-specific tiling arrays to analyze genetic material from a spontaneously aborted fetus with unbalanced segregation of the translocation. The chromosome 13 breakpoint was ∼400  kb away from the nearest gene, but the chromosome 9 breakpoint fell within an intron of Basonuclin 2 (BNC2), a gene that encodes an evolutionarily conserved nuclear zinc-finger protein. The BNC2/Bnc2 gene is abundantly expressed in developing mouse and human periurethral tissues. In all, 6 of 48 unrelated subjects with distal hypospadias had nine novel nonsynonymous substitutions in BNC2, five of which were computationally predicted to be deleterious. In comparison, two of 23 controls with normal penile urethra morphology, each had a novel nonsynonymous substitution in BNC2, one of which was predicted to be deleterious. Bnc2(-/-) mice of both sexes displayed a high frequency of distal urethral defects; heterozygotes showed similar defects with reduced penetrance. The association of BNC2 disruption with distal urethral defects and the gene's expression pattern indicate that it functions in urethral development.

Mutational Analysis of Androgen Receptor (AR) Gene in 46,XY Patients with Ambiguous Genitalia and Normal Testosterone Secretion: Endocrinological Characteristics of Three Patients with AR Gene Mutations

The prevalence of abnormalities in androgen receptor gene (AR) among patients with ambiguous genitalia is unknown. Moreover, endocrinological data from prepubertal patients with AR mutation are very limited. Thus, the aim of this study was to examine the prevalence of abnormalities in AR among patients with both ambiguous genitalia, which was defined as a combination of two or more genital abnormalities (i.e. hypospadias, microphallus (penile length < 25 mm), hypoplastic scrotum, bifid scrotum, undescended testis) in this study, and normal to elevated T levels. We also compared the endocrinological data of prepubertal patients with AR mutation and ambiguous genitalia with that of those without the AR mutation. We screened 26 Japanese prepubertal 46,XY patients (five from three families were included) with both ambiguous genitalia and normal to elevated T levels. Mutations in AR were found in three (two of the three were related). Among the 23 patients without mutation in AR, the steroid 5-alpha-reductase 2 gene (SRD5A2) was also examined in eight patients with elevated T/dehydrotestosterone ratio after the hCG (>10) or with undervirilized family members. No mutation in SRD5A2 was found. Characteristics of the three patients with mutation in AR were compared with the 23 patients without mutation. In two patients, basal T levels (0.3, 0.2 ng/ml) and peak T levels after the hCG tests (8.3, 8.5 ng/ml) tended to be higher, and the peak LH/ peak FSH ratios after the GnRH tests (4.6, 4.0) were higher than in patients without mutation, at the ages of 1 yr and 9 mo and 3 yr and 8 mo, respectively. In conclusion, an abnormality in either AR or SRD5A2 was not common among patients with ambiguous genitalia and normal testosterone secretion. Elevated peak LH/peak FSH ratio (≥4) after the GnRH test in addition to detectable basal T levels and elevated peak T levels after the hCG test may infer AR abnormality in prepubertal patients with ambiguous genitalia at the age of one and over, although further study is needed, because our data were limited.

SRD5A2 gene analysis in an Italian population of under-masculinized 46,XY subjects

OBJECTIVE

The differential diagnosis of male under-masculinization, including a wide spectrum of phenotypes and a heterogeneous genetic basis, is crucial for the correct management of the patients. To characterize an Italian population of under-masculinized males, we performed the molecular analysis of the SRD5A2 gene (2p23), encoding the 5alpha-reductase-2 enzyme that converts testosterone (T) to dihydrotestosterone (DHT), and is required for full masculinization of the male foetus.

DESIGN AND PATIENTS

Twenty-six Italian patients with 46,XY kariotype and various degrees of ambiguous genitalia were retrospectively selected for this study. Twelve of these patients, 10 of whom were referred for partial androgen insensitivity syndrome (PAIS), were raised as females; 15 were raised as males and all had a severe hypospadias. For most of the patients, the case histories and hormonal findings were incomplete but all could be included in the clinical characteristics of under-masculinization.

MEASUREMENT

For hormonal evaluation, T and DHT were measured by means of radioimmunoassay (RIA) and high-performance liquid chromatography (HPLC)-RIA methods, respectively. Genomic DNA of all patients and relatives was extracted from peripheral blood, the five exons of the SRD5A2 gene were amplified by polymerase chain reaction (PCR) and submitted to automatic sequencing.

RESULTS

Five known mutations affecting the NADPH binding function and one new mutation affecting the enzyme C-terminus were identified in a total of eight patients (two of whom were sisters). Five families were characterized, and in two patients only one affected allele was observed. The extension of the analysis to the regions flanking exons allowed the identification of a new polymorphism in intron 2, whose frequency was determined.

CONCLUSION

This first report of an Italian population underlines the importance of differential diagnoses in patients with under-masculinization. The lack of precise genotype-phenotype correlation in some of the mutations highlights the necessity to improve knowledge about the biochemical aspects of steroid 5alpha-reductase action and about the interactions of genetic and environmental factors.

New mutations, hotspots, and founder effects in Brazilian patients with steroid 5alpha-reductase deficiency type 2

Mutations of the steroid 5alpha-reductase type 2 (SRD5A2) gene in 46,XY subjects cause masculinization defects of varying degrees, due to reduced or impaired enzymatic activity. In this study, sequence abnormalities of the SRD5A2 gene were assessed by polymerase chain reaction with specific primers and automated sequencing analysis in DNA samples from 20 patients with suspected steroid 5alpha-reductase type 2 deficiency from 18 Brazilian families. Eleven subjects presented SRD5A2 homozygous single-base mutations (two first cousins and four unrelated patients with G183S, two with R246W, one with del642T, one with G196S, and one with 217_218insC plus the A49T variant in heterozygosis), whereas four were compound heterozygotes (one with Q126R/IVS3+1G>A, one with Q126R/del418T, and two brothers with Q126R/G158R). Three patients were heterozygous for A207D, G196S, and R266W substitutions. The V89L polymorphism was found in heterozygosis in one of them (with A207D) and in one case with an otherwise normal gene sequence. The A49T variant was also detected in heterozygosis in the second case without other sequencing abnormalities. Four patients harbor yet non-described SRD5A2 gene mutations: a single nucleotide deletion (del642T), a G158R amino acid substitution, a splice junction mutation (IVS3+1G>A), and the insertion of a cytosine (217_218insC) occurring at a CCCC motif. This is the first report of a single-nucleotide insertion in the coding sequence of the SRD5A2 gene. In addition to these new mutations, this investigation reveals the prevalence of G183S substitution among a subset of African-Brazilian patients and presents evidences of the recurrence of already known mutations.