Mutations of CXorf6 are associated with a range of severities of hypospadias

A New MAMLD1 Variant in an Infant With Microphallus and Hypospadias With Hormonal Pattern Suggesting Partial Hypogonadotropic Hypogonadism-Case Report

MAMLD1 (X chromosome) is one of the recognized genes related to different sex development. It is expressed in testis and ovaries and seems to be involved in fetal sex development and in adult reproductive function, including testosterone biosynthesis. However, its exact role remains unclear. Over 40 genetic variants have been described, mainly in male individuals and mostly associated with hypospadias. Although MAMLD1 has been shown to regulate the expression of the steroidogenic pathway, patients with MAMLD1 variants mostly show normal gonadal function and normal testosterone levels. Here we describe a patient (46,XY) with hypospadias and microphallus, with low testosterone and dihydrotestosterone (DHT) levels, and with inappropriately low values of luteinizing hormone (LH) during minipuberty. This hormonal pattern was suggestive of partial hypogonadotropic hypogonadism. A stimulation test with hCG (4 months) showed no significant increase in both testosterone and dihydrotestosterone concentrations. At 5 months of age, he was treated with intramuscular testosterone, and the penis length increased to 3.5 cm. The treatment was stopped at 6 months of age. Our gonadal function massive-sequencing panel detected a previously unreported nonsense variant in the MAMLD1 gene (c.1738C>T:p.Gln580Ter), which was classified as pathogenic. This MAMLD1 variant, predicting a truncated protein, could explain his genital phenotype. His hormonal profile (low testosterone, dihydrotestosterone, and LH concentrations) together with no significant increase of testosterone and DHT plasma concentrations (hCG test) highlight the potential role of this gene in the biosynthesis of testosterone during the fetal stage and minipuberty of the infant. Besides this, the LH values may suggest an involvement of MAMLD1 in the LH axis or a possible oligogenesis. It is the first time that a decrease in DHT has been described in a patient with an abnormal MAMLD1.

MAMLD1 and Differences/Disorders of Sex Development: An Update

MAMLD1 (alias CXorf6) was first documented in 2006 as a causative gene of 46,XY differences/disorders of sex development (DSD). MAMLD1/Mamld1 is expressed in the fetal testis and is predicted to enhance the expression of several Leydig cell-specific genes. To date, hemizygous MAMLD1 variants have been identified in multiple 46,XY individuals with hypomasculinized external genitalia. Pathogenic MAMLD1 variants are likely to cause genital abnormalities at birth and are possibly associated with age-dependent deterioration of testicular function. In addition, some MAMLD1 variants have been identified in 46,XX individuals with ovarian dysfunction. However, recent studies have raised the possibility that MAMLD1 variants cause 46,XY DSD and ovarian dysfunction as oligogenic disorders. Unsolved issues regarding MAMLD1 include the association between MAMLD1 variants and 46,XX testicular DSD, gene-gene interactions in the development of MAMLD1-mediated DSD, and intracellular functions of MAMLD1.

Oligogenic Causes of Human Differences of Sex Development: Facing the Challenge of Genetic Complexity

BACKGROUND

Deviations of intrauterine sex determination and differentiation and postnatal sex development can result in a very heterogeneous group of differences of sex development (DSD) with a broad spectrum of phenotypes. Variants in genes involved in sexual development cause different types of DSD, but predicting the phenotype from an individual's genotype and vice versa remains challenging.

SUMMARY

Next Generation Sequencing (NGS) studies suggested that oligogenic inheritance contributes to the broad manifestation of DSD phenotypes. This review will focus on possible oligogenic inheritance in DSD identified by NGS studies with a special emphasis on NR5A1variants as an example of oligogenic origin associated with a broad range of DSD phenotypes. We thoroughly searched the literature for evidence regarding oligogenic inheritance in DSD diagnosis with NGS technology and describe the challenges to interpret contribution of these genes to DSD phenotypic variability and pathogenicity. Key Messages: Variants in common DSD genes like androgen receptor (AR), mitogen-activated protein kinase kinase kinase 1 (MAP3K1), Hydroxy-Delta-5-Steroid Dehydrogenase 3 Beta- And Steroid Delta-Isomerase 2 (HSD3B2), GATA Binding Protein 4 (GATA4), zinc finger protein friend of GATA family member 2 (ZFPM2), 17b-hydroxysteroid dehydrogenase type 3 (HSD17B3), mastermind-like domain-containing protein 1 (MAMLD1), and nuclear receptor subfamily 5 group A member 1 (NR5A1) have been detected in combination with additional variants in related genes in DSD patients with a broad range of phenotypes, implying a role of oligogenic inheritance in DSD, while still awaiting proof. Use of NGS approach for genetic diagnosis of DSD patients can reveal more complex genetic traits supporting the concept of oligogenic cause of DSD. However, assessing the pathomechanistic contribution of multiple gene variants on a DSD phenotype remains an unsolved conundrum.

Etiology of Hypospadias: A Comparative Review of Genetic Factors and Developmental Processes Between Human and Animal Models

Hypospadias is a congenital anomaly of the penis with an occurrence of approximately 1 in 200 boys, but the etiology of the majority of hypospadias has remained unknown. Numerous genes have been reported as having variants in hypospadias patients, and many studies on genetic deletion of key genes in mouse genital development have also been published. Until now, no comparative analysis in the genes related literature has been reported. The basic knowledge of penile development and hypospadias is mainly obtained from animal model studies. Understanding of the differences and similarities between human and animal models is crucial for studies of hypospadias. In this review, mutations and polymorphisms of hypospadias-related genes have been compared between humans and mice, and differential genotype–phenotype relationships of certain genes between humans and mice have been discussed using the data available in PubMed and MGI online databases, and our analysis only revealed mutations in seven out of 43 human hypospadias related genes which have been reported to show similar phenotypes in mutant mice. The differences and similarities in the processes of penile development and hypospadias malformation among human and commonly used animal models suggest that the guinea pig may be a good model to study the mechanism of human penile development and etiology of hypospadias.

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.

Broad Phenotypes of Disorders/Differences of Sex Development in MAMLD1 Patients Through Oligogenic Disease

Disorders/differences of sex development (DSD) are the result of a discordance between chromosomal, gonadal, and genital sex. DSD may be due to mutations in any of the genes involved in sex determination and development in general, as well as gonadal and/or genital development specifically. MAMLD1 is one of the recognized DSD genes. However, its role is controversial as some MAMLD1 variants are present in normal individuals, several MAMLD1 mutations have wild-type activity in functional studies, and the Mamld1-knockout male mouse presents with normal genitalia and reproduction. We previously tested nine MAMLD1 variants detected in nine 46,XY DSD patients with broad phenotypes for their functional activity, but none of the mutants, except truncated L210X, had diminished transcriptional activity on known target promoters CYP17A1 and HES3. In addition, protein expression of MAMLD1 variants was similar to wild-type, except for the truncated L210X. We hypothesized that MAMLD1 variants may not be sufficient to explain the phenotype in 46,XY DSD individuals, and that further genetic studies should be performed to search for additional hits explaining the broad phenotypes. We therefore performed whole exome sequencing (WES) in seven of these 46,XY patients with DSD and in one 46,XX patient with ovarian insufficiency, who all carried MAMLD1 variants. WES data were filtered by an algorithm including disease-tailored lists of MAMLD1-related and DSD-related genes. Fifty-five potentially deleterious variants in 41 genes were identified; 16/55 variants were reported in genes in association with hypospadias, 8/55 with cryptorchidism, 5/55 with micropenis, and 13/55 were described in relation with female sex development. Patients carried 1-16 variants in 1-16 genes together with their MAMLD1 variation. Network analysis of the identified genes revealed that 23 genes presented gene/protein interactions with MAMLD1. Thus, our study shows that the broad phenotypes of individual DSD might involve multiple genetic variations contributing towards the complex network of sexual development.

Polymorphisms of MAMLD1, SRD5A2, and AR Candidate Genes in Seven Dogs (78,XY; SRY-Positive) Affected by Hypospadias or Cryptorchidism

Knowledge of the molecular background of disorders of sex development (DSD) in dogs with normal sets of XY chromosomes (XY DSD) is very scarce. However, extensive studies have been carried out in humans, showing that polymorphisms and mutations of numerous genes, including SRY, MAMLD1, SRD5A2, and AR, are associated with or responsible for XY DSD. In this study, we analyzed the entire coding sequence of these genes in 7 dogs (78,XY) with ambiguous external genitalia (hypospadias, cryptorchidism, bifid scrotum, or rudimentary penis). The most common disorder was hypospadias (6 cases), followed by cryptorchidism (4 cases). The co-occurrence of both abnormalities was observed in 3 dogs. Polymorphisms were found in MAMLD1 (3 SNPs), SRD5A2 (5 SNPs), and AR (2 STRs and 1 SNP), while SRY was monomorphic. However, the distribution of the polymorphic variants in the DSD dogs and 11 control XY dogs did not differ significantly. Our study suggests that an association between the polymorphisms of the studied candidate genes and hypospadias or cryptorchidism is unlikely in dogs. We thus support the recent suggestion that hypospadias is not rare in this species, and moreover, we show that co-occurrence of hypospadias and cryptorchidism can be quite frequent.

The structure-activity relationship (SAR) for phthalate-mediated developmental and reproductive toxicity in males

Testicular dysgenesis syndrome includes the hypospadias, cryptorchidism and abnormal fetal testis in male neonate. This is possibly caused by the environmental phthalates, which down-regulate the expression of androgen synthetic genes and Insl3 or directly inhibits steroidogenic enzymes. There are distinct structure-activity relationships (SARs) for phthalate-mediated developmental and reproductive toxicity. Here, we review the SAR for phthalate-mediated testicular dysgenesis syndrome. Of phthalates of straight side chains, C5-C6 ones are the most potent, C4 or C7 are moderate, C3 is weakest, and C1-2 or C8-13 are ineffective. The branching and unsaturation of side chains increases the toxicity. The cycling of side chains does not increase the toxicity.

Molecular genetics of hypospadias and cryptorchidism recent developments

During the last decade, a tremendous amount of work has been devoted to the study of the molecular genetics of isolated hypospadias and cryptorchidism, two minor forms of disorders of sex development (DSD). Beyond the genes involved in gonadal determination and sex differentiation, including those underlying androgen biosynthesis and signaling, new genes have been identified through genome-wide association study and familial clustering. Even if no single genetic defect can explain the whole spectrum of DSD, these recent studies reinforce the strong role of the genetic background in the occurrence of these defects. The timing of signaling disruption may explain the different phenotypes.

Description of a novel variant in the MAMLD1 gene in isolated hypospadias

Introduction Hypospadias is a multifactorial malformation. Among previously described genes, the MAMLD1 has recently been identified in association with the development of hypospadias. So far, there are no studies in Latin America addressing this gene. The aim of this paper is to describe the presence of variants in exon 3 of the MAMLD1 in our population.

Materials and Methods Using the Bio-Repository's database of the Human Genetics Institute, we identified 51 patients between 2008 and 2012 with varying degrees of isolated hypospadias. Exon 3 was sequenced looking for polymorphisms. These were assessed with in silico prediction algorithms to describe the effect of these changes on the function and structure of the protein.

Results Four patients with 3 variants were identified. The p.S364P variant has not been previously described and has a deleterious effect. The other two, rs41313406 and rs61740566, have been previously described and are not considered variations with harmful effect on the protein function. The genotype-phenotype correlation varies in severity between the variables described.

Conclusions For the first time a Latin American population is molecularly analyzed. The p.S364P variation has never been described before. Variations with different degrees of hypospadias are described.

Knockout of Murine Mamld1 Impairs Testicular Growth and Daily Sperm Production but Permits Normal Postnatal Androgen Production and Fertility

MAMLD1 has been implicated in testicular function in both human and mouse fetuses. Although three patients with MAMLD1 mutations were reported to have hypergonadotropic hypogonadism in their teens, the functional significance of MAMLD1 in the postnatal testis remains unclear. Here, we analyzed the phenotype of Mamld1 knockout (KO) male mice at reproductive ages. The reproductive organs of KO male mice were morphologically unremarkable, except for relatively small testes. Seminiferous tubule size and number of proliferating spermatogonia/spermatocytes were reduced in the KO testis. Daily sperm production of KO mice was mildly attenuated, whereas total sperm counts in epididymal semen remained normal. Sperm motility and morphology, as well as androgen levels in serum and testicular tissues and the number of pups born from cross-mated wildtype (WT) female mice, were comparable between WT and KO male mice. These results indicate that MAMLD1 contributes to the maintenance of postnatal testicular growth and daily sperm production but is dispensable for androgen biosynthesis and fertility. MAMLD1 likely plays supporting roles in multiple and continuous steps of male reproduction.

A validated protocol to quantify severity of male urogenital feminization using the MOUSE (Mouse objective urethral severity evaluation)

BACKGROUND

Congenital abnormalities vary in presentation, yet studies using model organisms tend to focus on occurrence rather than severity of the defect. Scoring severity of abnormalities in model systems allows explicit hypothesis testing during basic, translational, and reverse translational studies. We developed and validated a protocol to quantify severity of male urogenital feminization (hypospadias) in the mouse model. Hypospadias is one of the most common birth defects in the world.

METHODS

To induce genital feminization, pregnant mice were exposed to different concentrations of the antiandrogen vinclozolin. Genitalia were photographed at gestational age 18.5. A dichotomous scoring system to evaluate genital feminization was developed, and validated against histological measurements of urethral length. A training protocol was developed for novice scorers, and criteria were defined to evaluate precision and accuracy of scores.

RESULTS

Vinclozolin induced variation in hypospadias severity. Severity scores were tightly correlated with histologically determined urethral length and both techniques showed similar dose-response relationships. Novice observers were trained to precisely and accurately score hypospadias severity.

CONCLUSION

This standardized scoring system advances the mouse as a model to study urogenital development, and will facilitate research on the mechanisms driving genital feminization in males, and aid translational hypospadias research.

Long-term clinical course in three patients with MAMLD1 mutations

Although MAMLD1 on chromosome Xq28 is known as a causative gene for 46,XY disorders of sex development, clinical information is virtually limited in patients of infancy to early childhood. Here, we report long-term genital and hormonal findings in three previously described Japanese patients with MAMLD1 mutations, i.e., patients 1 and 2 with p.E197X and patient 3 with p.R726X. As previously reported, patients 1-3 exhibited penoscrotal hypospadias with chordee, microphallus, bifid/hypoplastic scrotum, and/or bilateral cryptorchidism/retractile testes, in the presence of sufficiently high serum basal or hCG-stimulated testosterone values in the mini-pubertal period to early childhood. Subsequently, patient 1 had low serum hCG-stimulated testosterone value (126 ng/dL) at 13 11/12 years of age, and manifested microphallus (4.5 cm), relatively small testes (left 8 mL and right 10 mL), Tanner stage 3 genitalia and pubic hair development at 18 3/12 years of age. Similarly, patients 2 and 3 showed mild hypergonadotropic hypogonadism at 7 0/12 and 9 9/12 years of age, respectively, with serum GnRH-stimulated LH values of 5.5 and 7.2 mIU/mL and FSH values of 10.3 and 19.8 mIU/mL and hCG-stimulated testosterone values of 70 and 80 ng/dL, respectively. Testis ultrasound studies delineated microlithiasis in patients 1 and 3. These results imply for the first time deterioration of testicular function with age in patients with pathologic MAMLD1 mutations.

Polymorphism of 3' UTR of MAMLD1 gene is also associated with increased risk of isolated hypospadias in Indian children: a preliminary report

OBJECTIVE

To study MAMLD1 gene polymorphisms, serum LH and testosterone levels amongst Indian children with isolated hypospadias (IH) and controls.

MATERIALS AND METHODS

Screening of the MAMLD1 gene was performed by PCR sequencing method in 100 Indian children aged 0-12 years presenting with IH and 100 controls. LH and testosterone hormone levels were also assessed (categorized in four age-wise groups).

RESULTS

IH subjects had significantly higher incidence of MAMLD1 polymorphism as compared to controls (33 vs 15 %, p = 0.01). Of various genomic variants identified in this study, the noteworthy novel ones were missense mutation P299A and single nucleotide polymorphism c.2960C>T in 3' UTR of Exon 7. While p 299A was found to cause protein structural instability consequent to amino acid change, eighty percent subjects with c.2960C>T in 3' UTR of Exon 7 (corresponding to newly discovered currently non-validated exon 11) were found to have lower testosterone levels when compared with their age group mean. IH showed statistically higher incidence of c.2960C>T in comparison to controls (22 vs 10 %, p value 0.046) and about 2.5-folds higher risk of this anomaly.

CONCLUSION

Occurrence of MAMDL1 gene polymorphisms, specially of c.2960C>T in 3' UTR of its exon 7 is associated with a higher risk of IH in Indian children, probably by lowering androgenic levels.

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.

Human MAMLD1 Gene Variations Seem Not Sufficient to Explain a 46,XY DSD Phenotype

MAMLD1 is thought to cause disordered sex development in 46,XY patients. But its role is controversial because some MAMLD1 variants are also detected in normal individuals, several MAMLD1 mutations have wild-type activity in functional tests, and the male Mamld1-knockout mouse has normal genitalia and reproduction. Our aim was to search for MAMLD1 variations in 108 46,XY patients with disordered sex development, and to test them functionally. We detected MAMDL1 variations and compared SNP frequencies in controls and patients. We tested MAMLD1 transcriptional activity on promoters involved in sex development and assessed the effect of MAMLD1 on androgen production. MAMLD1 expression in normal steroid-producing tissues and mutant MAMLD1 protein expression were also assessed. Nine MAMLD1 mutations (7 novel) were characterized. In vitro, most MAMLD1 variants acted similarly to wild type. Only the L210X mutation showed loss of function in all tests. We detected no effect of wild-type or MAMLD1 variants on CYP17A1 enzyme activity in our cell experiments, and Western blots revealed no significant differences for MAMLD1 protein expression. MAMLD1 was expressed in human adult testes and adrenals. In conclusion, our data support the notion that MAMLD1 sequence variations may not suffice to explain the phenotype in carriers and that MAMLD1 may also have a role in adult life.

Parturition failure in mice lacking Mamld1

In mice, the onset of parturition is triggered by a rapid decline in circulating progesterone. Progesterone withdrawal occurs as a result of functional luteolysis, which is characterized by an increase in the enzymatic activity of 20α-hydroxysteroid dehydrogenase (20α-HSD) in the corpus luteum and is mediated by the prostaglandin F2α (PGF_2α) signaling. Here, we report that the genetic knockout (KO) of Mamld1, which encodes a putative non-DNA-binding regulator of testicular steroidogenesis, caused defective functional luteolysis and subsequent parturition failure and neonatal deaths. Progesterone receptor inhibition induced the onset of parturition in pregnant KO mice, and MAMLD1 regulated the expression of Akr1c18, the gene encoding 20α-HSD, in cultured cells. Ovaries of KO mice at late gestation were morphologically unremarkable; however, Akr1c18 expression was reduced and expression of its suppressor Stat5b was markedly increased. Several other genes including Prlr, Cyp19a1, Oxtr, and Lgals3 were also dysregulated in the KO ovaries, whereas PGF_2α signaling genes remained unaffected. These results highlight the role of MAMLD1 in labour initiation. MAMLD1 likely participates in functional luteolysis by regulating Stat5b and other genes, independent of the PGF_2α signaling pathway.

Genetic and environmental factors in the aetiology of hypospadias

This article reviews the current evidence and knowledge of the aetiology of hypospadias. Hypospadias remains a fascinating anomaly of the male phallus. It may be an isolated occurrence or part of a syndrome or field defect. The increasing use of assisted reproductive techniques and hormonal manipulation during pregnancy may have been associated with an apparent rise in the incidence of hypospadias. Genetic studies and gene analysis have suggested some defects that could result in hypospadias. New light has also been thrown on environmental factors that could modulate candidate genes, causing altered development of the male external genitalia.

Novel Splice Site Mutation in MAMLD1 in a Patient with Hypospadias

MAMLD1 is a causative gene for disorders of sex development. Several MAMLD1 mutations have been shown to cause hypospadias by generating dysfunctional proteins and/or unstable mRNAs. Here, we identified an intronic mutation of MAMLD1 (g.IVS4-2A>G) in 1 of 180 hypospadias patients. RT-PCR of the patient's skin sample showed normal expression of full-length MAMLD1 and markedly reduced expression of a known splice variant lacking exon 4. A hitherto unreported splice variant that lacks exon 5 was similarly identified in samples of the patient and control individuals. The full-length transcript of the patient contained mutant mRNA lacking the first 10 nucleotides of exon 5 (c.1822_1831delACTCATGTAG, p.K609fsX1070). In vitro assays using cells expressing the full-length wild-type and mutant proteins revealed reduced expression of the mutant. The expression of the wild-type and mutant MAMLD1 showed parallel changes upon treatment with a proteasome inhibitor and a translation inhibitor. The mutant-expressing cells exerted low transactivation activity for the Hes3 promoter, which reflected limited expression of the mutant protein. These results imply that the pathogenic events resulting from MAMLD1 mutations include splice errors. Furthermore, this study raises the possibility of translation failure of MAMLD1 mutants, which deserves further investigation.

Review of genetic and environmental factors leading to hypospadias

Hypospadias is one of the most common congenital malformations, affecting about 4-6 males per 1000 male births, and ranging in severity from a urethral meatus that is slightly off-center to a meatus in the perineal area. Over the past three decades its prevalence may have increased due to changes in reporting of mild cases and/or increased survival of low birth weight infants due to improved neonatal care. However, despite the increasing numbers of males with hypospadias, the overall etiology remains unclear and likely multifactorial in nature. The purpose of this review article is to provide a comprehensive overview of the various factors implicated in hypospadias etiology, including genetic and environmental factors. In addition, we list syndromes in which hypospadias is a relatively common association and delineate the areas that require further investigation in an effort to understand this condition.

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.

Understanding the genetic aetiology in patients with XY DSD

BACKGROUND

Disorders of sex development (DSD) consist of a wide range of disorders and are commoner in those with an XY karyotype. In over half of these cases who have a 46,XY karyotype and who are raised as boys, the underlying aetiology remains unclear.

AREAS OF AGREEMENT

Identification of the underlying genetic abnormality may predict long-term outcome. However, genetic abnormalities that are associated with XY DSD manifest themselves with a wide range of phenotype. To understand the aetiology as well as the phenotypic variation, there is a need to harness the advanced genetic technology that is now available.

AREAS OF CONTROVERSY

The point at which genetic analysis should be undertaken in the course of investigations is unclear. In addition, there is little agreement on the most effective approach for genetic analysis that will be of clinical benefit to the patient.

AREAS TIMELY FOR DEVELOPING RESEARCH

There is a need to understand and improve the clinical utility of genetic analysis in the clinical setting of the patient with a suspected DSD. This will be even more important when parallel gene sequencing identifies variations in multiple genes.

X-linked congenital adrenal hypoplasia associated with hypospadias in an Egyptian baby: a case report

Introduction

X-linked congenital adrenal hypoplasia is a rare developmental disorder of the human adrenal cortex and is caused by deletion or mutation of the dosage-sensitive sex reversal adrenal hypoplasia congenita critical region of the X chromosome, gene 1 (DAX-1) gene. Most affected children present with failure to thrive, salt wasting and hypoglycemic convulsions in the first months of life. Hypospadias affects approximately one in 250 live male births. Mutations in the mastermind-like domain-containing 1 (MAMLD1) gene have been implicated as one of the causes of hypospadias in children. To the best of our knowledge, an association between congenital adrenal hypoplasia due to a DAX-1 mutation and hypospadias due to mutation of the MAMLD1 gene has not previously been reported in the literature.

Case presentation

A 35-day-old male Egyptian baby was referred to our institution for the evaluation of a two-week history of recurrent vomiting associated with electrolyte imbalance. On examination, our patient was found to have hypotension and dehydration. A genital examination showed distal penile hypospadias with chordee and normal testes. He had hyponatremia, hyperkalemia, hypoglycemia and metabolic acidosis. Endocrinological investigations revealed low levels of cortisol, 17-hydroxyprogesterone and aldosterone, with a high level of adrenocorticotrophic hormone. A provisional diagnosis of congenital adrenal hypoplasia associated with hypospadias was made. A molecular genetics study confirmed the diagnosis of X-linked congenital adrenal hypoplasia due to DAX-1 mutations and hypospadias due to MAMLD1 mutation. He was started on hydrocortisone and fludrocortisone treatment. After three weeks of treatment, his symptoms improved and his blood sugar, sodium, potassium and cortisol levels normalized.

Conclusions

We report the case of an Egyptian baby with an association of congenital adrenal hypoplasia due to DAX-1 mutation and hypospadias due to MAMLD1 mutation. Early diagnosis of this association and determining its optimal treatment are vital in helping to avoid its fatal course.

Mamld1 deficiency significantly reduces mRNA expression levels of multiple genes expressed in mouse fetal Leydig cells but permits normal genital and reproductive development

Although mastermind-like domain containing 1 (MAMLD1) (CXORF6) on human chromosome Xq28 has been shown to be a causative gene for 46,XY disorders of sex development with hypospadias, the biological function of MAMLD1/Mamld1 remains to be elucidated. In this study, we first showed gradual and steady increase of testicular Mamld1 mRNA expression levels in wild-type male mice from 12.5 to 18.5 d postcoitum. We then generated Mamld1 knockout (KO) male mice and revealed mildly but significantly reduced testicular mRNA levels (65-80%) of genes exclusively expressed in Leydig cells (Star, Cyp11a1, Cyp17a1, Hsd3b1, and Insl3) as well as grossly normal testicular mRNA levels of genes expressed in other cell types or in Leydig and other cell types. However, no demonstrable abnormality was identified for cytochrome P450 17A1 and 3β-hydroxysteroid dehydrogenase (HSD3B) protein expression levels, appearance of external and internal genitalia, anogenital distance, testis weight, Leydig cell number, intratesticular testosterone and other steroid metabolite concentrations, histological findings, in situ hybridization findings for sonic hedgehog (the key molecule for genital tubercle development), and immunohistochemical findings for anti-Müllerian hormone (Sertoli cell marker), HSD3B (Leydig cell marker), and DEAD (Asp-Glu-Ala-Asp) box polypeptide 4 (germ cell marker) in the KO male mice. Fertility was also normal. These findings imply that Mamld1 deficiency significantly reduces mRNA expression levels of multiple genes expressed in mouse fetal Leydig cells but permits normal genital and reproductive development. The contrastive phenotypic findings between Mamld1 KO male mice and MAMLD1 mutation positive patients would primarily be ascribed to species difference in the fetal sex development.

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.

Screening of MAMLD1 mutations in 70 children with 46,XY DSD: identification and functional analysis of two new mutations

More than 50% of children with severe 46,XY disorders of sex development (DSD) do not have a definitive etiological diagnosis. Besides gonadal dysgenesis, defects in androgen biosynthesis, and abnormalities in androgen sensitivity, the Mastermind-like domain containing 1 (MAMLD1) gene, which was identified as critical for the development of male genitalia, may be implicated. The present study investigated whether MAMLD1 is implicated in cases of severe 46,XY DSD and whether routine sequencing of MAMLD1 should be performed in these patients.

Seventy children with severe non-syndromic 46,XY DSD of unknown etiology were studied. One hundred and fifty healthy individuals were included as controls. Direct sequencing of the MAMLD1, AR, SRD5A2 and NR5A1 genes was performed. The transactivation function of the variant MAMLD1 proteins was quantified by the luciferase method.

Two new mutations were identified: p.S143X (c.428C>A) in a patient with scrotal hypospadias with microphallus and p.P384L (c.1151C>T) in a patient with penile hypospadias with microphallus. The in vitro functional study confirmed no residual transactivating function of the p.S143X mutant and a significantly reduced transactivation function of the p.P384L protein (p = 0.0032). The p.P359S, p.N662S and p.H347Q variants are also reported with particularly high frequency of the p.359T- p.662G haplotype in the DSD patients.

Severe undervirilization in XY newborns can reveal mutations of MAMLD1. MAMLD1 should be routinely sequenced in these patients with otherwise normal AR, SRD5A2 and NR5A1genes.

Aetiology of hypospadias: a systematic review of genes and environment

BACKGROUND

Hypospadias is a common congenital malformation of the male external genitalia. Most cases have an unknown aetiology, which is probably a mix of monogenic and multifactorial forms, implicating both genes and environmental factors. This review summarizes current knowledge about the aetiology of hypospadias.

METHODS

Pubmed was used to identify studies on hypospadias aetiology published between January 1995 and February 2011. Reference lists of the selected manuscripts were also searched to identify additional studies, including those published before 1995.

RESULTS

The search provided 922 articles and 169 articles were selected for this review. Studies screening groups of patients with hypospadias for single gene defects found mutations in WT1, SF1, BMP4, BMP7, HOXA4, HOXB6, FGF8, FGFR2, AR, HSD3B2, SRD5A2, ATF3, MAMLD1, MID1 and BNC2. However, most investigators are convinced that single mutations do not cause the majority of isolated hypospadias cases. Indeed, associations were found with polymorphisms in FGF8, FGFR2, AR, HSD17B3, SRD5A2, ESR1, ESR2, ATF3, MAMLD1, DGKK, MID1, CYP1A1, GSTM1 and GSTT1. In addition, gene expression studies indentified CTGF, CYR61 and EGF as candidate genes. Environmental factors consistently implicated in hypospadias are low birthweight, maternal hypertension and pre-eclampsia, suggesting that placental insufficiency may play an important role in hypospadias aetiology. Exogenous endocrine-disrupting chemicals have the potential to induce hypospadias but it is unclear whether human exposure is high enough to exert this effect. Other environmental factors have also been associated with hypospadias but, for most, the results are inconsistent.

CONCLUSIONS

Although a number of contributors to the aetiology of hypospadias have been identified, the majority of risk factors remain unknown.

Polymorphisms of MAMLD1 gene in hypospadias

PURPOSE

Mastermind-like domain containing 1 (MAMLD1) is a causative gene for the fetal development of male external genitalia. Almost 10% of patients with both severe and non-severe hypospadias exhibit mutations of MAMLD1. The aim of this work was to determine whether polymorphisms of MAMLD1 are a genetic risk factor for hypospadias.

MATERIAL AND METHODS

This study included 150 hypospadias with a range of severities and 150 controls. Direct sequencing of the MAMLD1 coding exons and their flanking splice sites was performed. In silico secondary and tertiary structure prediction and accessibility of changed amino acids were evaluated using JPred, Netsurf and PHYRE software. Functional studies of the transactivation of haplotypes on Hes3 promoter were performed in vitro using cDNAs of missense variants of MAMLD1.

RESULTS

The p.P286S polymorphism was identified in 17/150 patients and 12/150 controls (11.3% vs. 8.0%, p = 0.32). The p.N589S polymorphism was identified in 22/150 patients and 12/150 controls (14.6% vs. 8.0%, p = 0.068). The double polymorphism (S-S haplotype) was present in 16/150 patients and 6/150 controls (10.6% vs. 4.0%, p = 0.044, OR = 2.87, CI from 1.09 to 7.55). The association of polymorphisms consistently revealed a modification in the structure prediction or amino acid accessibility in all three in silico models. The P286S, N589S and P286S + N589S proteins did not exhibit reduced transactivating activity on Hes3 promoter.

CONCLUSION

Polymorphisms of MAMLD1 gene are frequent in patients with hypospadias. Although no change in transactivation was noted on Hes3 promoter, the in silico studies and the significantly increased incidence of the S-S haplotype in hypospadiac patients raise the hypothesis of a particular susceptibility conferred by these variants.

'Idiopathic' partial androgen insensitivity syndrome in 28 newborn and infant males: impact of prenatal exposure to environmental endocrine disruptor chemicals?

OBJECTIVE

46,XY disorders of sex differentiation (46,XY DSD) can be due to a testis determination defect, an androgen biosynthesis defect, or androgen resistance (complete or partial androgen insensitivity syndrome (PAIS), or 5α reductase deficiency). We aimed to evaluate the impact of a prenatal contamination by environmental xenoestrogens in 'idiopathic' PAIS-like phenotype.

SUBJECTS

We investigated 28 newborn/infant males with 46,XY DSD, normal androgen production, and no androgen receptor or steroid-5αR type II enzyme (SRD5A2) gene mutations.

METHODS

To exclude other genetic defects, we sequenced the steroidogenic factor 1 (SF1) and mastermind-like domain-containing 1 (MAMLD1) genes, which were recently found to be associated with the PAIS-like phenotype. Parents were interviewed about their environmental/occupational exposure to endocrine disrupting chemicals (EDCs) before/during the patients' fetal life. Total estrogenic bioactivity of patient serum was analyzed by ultrasensitive bioassay.

RESULTS

All the patients had normal SF1 sequence and one patient showed a double polymorphism of MAMLD1. Eleven (39.3%) of the 28 patients had reported parental fetal exposure to EDCs. The mean estrogenic bioactivity in these 11 patients with fetal EDC exposure (6.65 ± 8.07 pg/ml) versus 17 cases without contamination (1.27 ± 0.34 pg/ml) and controls (1.06 ± 0.44 pg/ml; P<0.05) was elevated.

CONCLUSIONS

Our results indicate that the 'idiopathic' PAIS-like phenotype may in some cases be related to EDC contamination during fetal life.

Prenatal environmental risk factors for genital malformations in a population of 1442 French male newborns: a nested case-control study

BACKGROUND

Over the past decades, an increasing trend in male external genital malformations such as cryptorchidism and hypospadias has led to the suspicion that environmental chemicals are detrimental to male fetal sexual development. Several environmental pollutants, including organochlorine pesticides, polychlorinated biphenyls, bisphenol A, phthalates, dioxins and furans have estrogenic and anti-androgenic activity and are thus considered as endocrine-disrupting chemicals (EDCs). Since male sex differentiation is critically dependent on the normal production and action of androgens during fetal life, EDCs may be able to alter normal male sex differentiation.

OBJECTIVE

The objective of this study was to determine the incidence of external genital malformations in a population of full-term newborn males in southern France. We also performed a case-control study to identify the risk factors for male external genital malformations, with a focus on parental occupational exposure to EDCs.

METHODS

Over a 16-month period, 1615 full-term newborn males with a birth weight above 2500 g were registered on a level-1 maternity ward, and the same pediatrician systematically examined 1442 of them (89%) for cryptorchidism, hypospadias and micropenis. For every male newborn with genital malformation, we enrolled nearly two males matched for age, parity and term. All parents of the case and control newborns were interviewed about pregnancy aspects, personal characteristics, lifestyle and their occupational exposure to EDCs using a detailed questionnaire. RESULTS We report 39 cases of genital malformation (2.70%), with 18 cases of cryptorchidism (1.25%), 14 of hypospadias (0.97%), 5 of micropenis (0.35%) and 2 of 46,XY disorders of sexual differentiation (DSD; 0.14%). We observed a significant relationship between newborn cryptorchidism, hypospadias or micropenis and parental occupational exposure to pesticides [odds ratio (OR) = 4.41; 95% confidence interval (95% CI), 1.21-16.00]. Familial clustering for male external genital malformations (OR = 7.25; 95% CI, 0.70-74.30) and medications taken by mothers during pregnancy (OR = 5.87; 95% CI, 0.93-37.00) were associated with the risk of cryptorchidism, hypospadias and micropenis, although the association was not statistically significant.

CONCLUSIONS

Although the causes of male genital malformation are multifactorial, our data support the hypothesis that prenatal contamination by pesticides may be a potential risk factor for newborn male external genital malformation and it should thus be routinely investigated in all undervirilized newborn males.

Mamld1 knockdown reduces testosterone production and Cyp17a1 expression in mouse Leydig tumor cells

BACKGROUND

MAMLD1 is known to be a causative gene for hypospadias. Although previous studies have indicated that MAMLD1 mutations result in hypospadias primarily because of compromised testosterone production around the critical period for fetal sex development, the underlying mechanism(s) remains to be clarified. Furthermore, although functional studies have indicated a transactivation function of MAMLD1 for the non-canonical Notch target Hes3, its relevance to testosterone production remains unknown. To examine these matters, we performed Mamld1 knockdown experiments.

METHODOLOGY/PRINCIPAL FINDINGS

Mamld1 knockdown was performed with two siRNAs, using mouse Leydig tumor cells (MLTCs). Mamld1 knockdown did not influence the concentrations of pregnenolone and progesterone but significantly reduced those of 17-OH pregnenolone, 17-OH progesterone, dehydroepiandrosterone, androstenedione, and testosterone in the culture media. Furthermore, Mamld1 knockdown significantly decreased Cyp17a1 expression, but did not affect expressions of other genes involved in testosterone biosynthesis as well as in insulin-like 3 production. Hes3 expression was not significantly altered. In addition, while 47 genes were significantly up-regulated (fold change >2.0×) and 38 genes were significantly down-regulated (fold change <0.5×), none of them was known to be involved in testosterone production. Cell proliferation analysis revealed no evidence for compromised proliferation of siRNA-transfected MLTCs.

CONCLUSIONS/SIGNIFICANCE

The results, in conjunction with the previous data, imply that Mamld1 enhances Cyp17a1 expression primarily in Leydig cells and permit to produce a sufficient amount of testosterone for male sex development, independently of the Hes3-related non-canonical Notch signaling.

Hypospadias: interactions between environment and genetics

Hypospadias is one of the most common congenital malformations. It is considered to be a mild form of the 46,XY disorders of sex development (DSD), but its precise etiology remains to be elucidated. Compromised androgen synthesis or effects can cause this frequent malformation, although the mutational analyses of the genes involved in androgen actions have identified abnormalities in only a very small portion of patients. The overwhelming majority of cases remain unexplained and hypospadias may be a highly heterogeneous condition subject to multiple genetic and environmental factors. We here review the recent advances in this field and discuss the potential interactions between the environment and genetics.

Genetic pathway of external genitalia formation and molecular etiology of hypospadias

Hypospadias is one of the most common congenital disorders in males. Impaired fetal androgen action interferes with masculinization, including external genitalia formation, and can result in this anomaly; however, the molecular etiology remains unknown. Recent molecular approaches, including gene-targeting approaches in mice and single nucleotide polymorphisms analyses in humans, might provide an opportunity to identify the causative and risk factors of this anomaly. Several genes, such as sonic hedgehog, fibroblast growth factors, bone morphogenetic proteins, homeobox genes, and the Wnt family regulate external genitalia formation. Mastermind-like domain containing 1/chromosome X open reading frame 6 mutation and activating transcription factor 3 variants have been shown to be associated with the incidence of isolated hypospadias. In addition, this anomaly may be associated with a specific haplotype of the gene for estrogen receptor alpha, which mediates the estrogenic effects of environmental endocrine disruptors, and the effects of these disruptors on external genitalia formation might depend on individual genetic susceptibility. These molecular studies will refine our knowledge of the genetic mechanism involved in external genitalia formation, and lead to new strategies for the clinical management of hypospadias.

Comparative gene expression analysis of genital tubercle development reveals a putative appendicular Wnt7 network for the epidermal differentiation

Here we describe the first detailed catalog of gene expression in the developing lower urinary tract (LUT), including epithelial and mesenchymal portions of the developing bladder, urogenital sinus, urethra, and genital tubercle (GT) at E13 and E14. Top compartment-specific genes implicated by the microarray data were validated using whole-mount in situ hybridization (ISH) over the entire LUT. To demonstrate the potential of this resource to implicate developmentally critical features, we focused on gene expression patterns and pathways in the sexually indeterminate, androgen-independent GT. GT expression patterns reinforced the proposed similarities between development of GT, limb, and craniofacial prominences. Comparison of spatial expression patterns predicted a network of Wnt7a-associated GT-enriched epithelial genes, including Gjb2, Dsc3, Krt5, and Sostdc1. Known from other contexts, these genes are associated with normal epidermal differentiation, with disruptions in Dsc3 and Gjb2 showing palmo-plantar keratoderma in the limb. We propose that this gene network contributes to normal foreskin, scrotum, and labial development. As several of these genes are known to be regulated by, or contain cis elements responsive to retinoic acid, estrogen, or androgen, this implicates this pathway in the later androgen-dependent development of the GT.

An unusual association of hypospadias with partial deletion of chromosome 1q

OBJECTIVE

To report an unusual finding of chromosome 1q deletion in a man with failed multiple hypospadias repair.

DESIGN

Case report and discussion.

SETTING

An academic tertiary care hospital.

PATIENT(S)

A 32-year-old man with failed multiple hypospadias repair.

INTERVENTION(S)

Clinical, hormonal, cytogenetic evaluation, fluorescent in situ hybridization (FISH), and ultrasonography.

MAIN OUTCOME MEASURE(S)

Serum gonadotropin and testosterone levels, and karyotype showing structural abnormality of long arm of chromosome 1.

RESULT(S)

Ultrasonography showed the absence of the left testis and a hypoechoic right testis. Serum luteinizing hormone and follicular stimulating hormone levels were raised, but testosterone and prolactin levels were within the normal range for adult men. Karyotype analysis revealed an interstitial deletion of the long arm of chromosome 1, which was confirmed by FISH.

CONCLUSION(S)

Chromosome 1 may harbor a critical domain that is essential for male fertility.