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

46 XY disorder of sex development (DSD) due to 5 alpha (SRD5A2) deficiency - Experience from a multidisciplinary Pediatric Gender Clinic

BACKGROUND

SRD5A2 deficiency leads to incomplete masculinization of individuals with a 46 XY karyotype. A definitive diagnosis in early infancy facilitates decisions concerning choice of sex of rearing and management.

AIM

To review the clinical presentation, diagnosis, treatment and outcome of children with 46 XY DSD due to SRD5A2 deficiency at a Paediatric Gender Clinic.

STUDY DESIGN AND METHODS

Retrospective review of cases of SRD5A2 deficiency (2000-15) managed with a standard protocol at a multidisciplinary clinic. Demographic data, clinical presentation, physical findings, investigations (hormonal profile, imaging, genitoscopy), psychological evaluation (child, family), medical and surgical management, outcome and follow up were collated and analyzed.

RESULTS

There were 12 cases aged 3 days-14 years at presentation, 3 had parental consanguinity. Eight were reared as males and 4 as females. Specialist referral was sought for hypospadias (5), atypical genitalia (5) or incongruent pubertal masculinization (2). All had chordee, symmetrical inguinoscrotal gonads, rugose labioscrotum and proximal hypospadias (perineoscrotal -9, perineal -3). Both pubertal cases had significant masculinization and no gynecomastia. The median testosterone/dihydrotestosterone ratio was 22.1(IQR-8.6-55.7). Despite a classical phenotype, four (2 prepubertal, 2 pubertal) had a ratio <10. Genitoscopy showed urogenital sinus remnant (4) and hypoplastic verumontanum (5). Sex reassignment was done in 4. Surgical management was staged and completed by 4 years in those with infantile presentation. Besides correction of chordee and urethroplasty in 11, other procedures included orchidopexy (5), excision of a urogenital sinus remnant (4) and correction of penoscrotal transposition (4). The urethroplasty was single staged in 3. All operated cases were followed up (mean age at last follow up - 10.63 years, mean follow up period - 7.25 years). The overall cosmetic result was satisfactory, but the phallic structure remained relatively small across prepubertal period. Uroflowmetry curves were normal in 9. All showed penile tumescence/erection and two peripubertal cases had typical secondary sexual characters. All cases, including those with sex reassignment, have a well-adjusted male psyche.

DISCUSSION AND CONCLUSION

The diagnosis, management and longitudinal follow up of cases of SRD5A2 deficiency at a multidisciplinary gender clinic is presented. Diagnostic dilemmas with low T/DHT ratios remained in a third of cases. Most were diagnosed in infancy and assigned a male sex of rearing, all underwent staged masculinizing genitoplasty. Those with sex reassignment also fared well with comprehensive management after family counseling.

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.

Maternal Protein Restriction Alters the Expression of Proteins Related to the Structure and Functioning of the Rat Offspring Epididymis in an Age-Dependent Manner

Nutrition is an environmental factor able to activate physiological interactions between fetus and mother. Maternal protein restriction is able to alter sperm parameters associated with epididymal functions. Since correct development and functioning of the epididymides are fundamental for mammalian reproductive success, this study investigated the effects of maternal protein restriction on epididymal morphology and morphometry in rat offspring as well as on the expression of Src, Cldn-1, AR, ER, aromatase p450, and 5α-reductase in different stages of postnatal epididymal development. For this purpose, pregnant females were allocated to normal-protein (NP—17% protein) and low-protein (LP—6% protein) groups that received specific diets during gestation and lactation. After weaning, male offspring was provided only normal-protein diet until the ages of 21, 44, and 120 days, when they were euthanized and their epididymides collected. Maternal protein restriction decreased genital organs weight as well as crown-rump length and anogenital distance at all ages. Although the low-protein diet did not change the integrity of the epididymal epithelium, we observed decreases in tubular diameter, epithelial height and luminal diameter of the epididymal duct in 21-day-old LP animals. The maternal low-protein diet changed AR, ERα, ERβ, Src 416, and Src 527 expression in offspring epididymides in an age-dependent manner. Finally, maternal protein restriction increased Cldn-1 expression throughout the epididymides at all analyzed ages. Although some of these changes did not remain until adulthood, the insufficient supply of proteins in early life altered the structure and functioning of the epididymis in important periods of postnatal development.

Molecular Characterization of Two Known SRD5A2 Gene Variants in Mexican Patients With Disorder of Sexual Development

Background: The 5α-reductase type 2 deficiency (5α-RD2) is a specific form of disorder of sexual development (DSD). Pathogenic variants in the SRD5A2 gene, which encodes this enzyme, are responsible for 46,XY DSD.

Objective: The objective of the study was to investigate the genetic etiology of 46,XY DSD in two Mexican families with affected children.

Materials and methods: The SRD5A2 gene of the parents and affected children was screened in both families via polymerase chain reaction amplification and DNA direct sequencing. The role of genetic variants in enzymatic activity was tested by site-directed mutagenesis.

Results: Subject 1 presented two variants: p.Glu197Asp and p.Pro212Arg. Subject 2 was homozygous for the variant p.Glu197Asp. The two variants were reported in early studies. The directed mutagenesis study showed that the p.Glu197Asp and p.Pro212Arg variants lead to a total loss of enzymatic activity and, consequently, abnormal genitalia development in the patients.

Conclusion: These results suggest that p.Glu197Asp and p.Pro212Arg are pathogenic variants that lead to the phenotypic expression of DSD. 5α-RD2 is of extreme importance not only because of its frequency (it is rare) but also because of its significance in understanding the mechanism of androgen action, the process of sexual differentiation, and the factors that influence normal sexual behavior.

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.

Genotype-phenotype correlation, gonadal malignancy risk, gender preference, and testosterone/dihydrotestosterone ratio in steroid 5-alpha-reductase type 2 deficiency: a multicenter study from Turkey

BACKGROUND

Studies regarding genetic and clinical characteristics, gender preference, and gonadal malignancy rates for steroid 5-alpha-reductase type 2 deficiency (5α-RD2) are limited and they were conducted on small number of patients.

OBJECTIVE

To present genotype-phenotype correlation, gonadal malignancy risk, gender preference, and diagnostic sensitivity of serum testosterone/dihydrotestosterone (T/DHT) ratio in patients with 5α-RD2.

MATERIALS AND METHODS

Patients with variations in the SRD5A2 gene were included in the study. Demographic characteristics, phenotype, gender assignment, hormonal tests, molecular genetic data, and presence of gonadal malignancy were evaluated.

RESULTS

A total of 85 patients were included in the study. Abnormality of the external genitalia was the most dominant phenotype (92.9%). Gender assignment was male in 58.8% and female in 29.4% of the patients, while it was uncertain for 11.8%. Fourteen patients underwent bilateral gonadectomy, and no gonadal malignancy was detected. The most frequent pathogenic variants were p.Ala65Pro (30.6%), p.Leu55Gln (16.5%), and p.Gly196Ser (15.3%). The p.Ala65Pro and p.Leu55Gln showed more undervirilization than the p.Gly196Ser. The diagnostic sensitivity of stimulated T/DHT ratio was higher than baseline serum T/DHT ratio, even in pubertal patients. The cut-off values yielding the best sensitivity for stimulated T/DHT ratio were ≥ 8.5 for minipuberty, ≥ 10 for prepuberty, and ≥ 17 for puberty.

CONCLUSION

There is no significant genotype-phenotype correlation in 5α-RD2. Gonadal malignancy risk seems to be low. If genetic analysis is not available at the time of diagnosis, stimulated T/DHT ratio can be useful, especially if different cut-off values are utilized in accordance with the pubertal status.

Molecular diagnostics of disorders of sexual development: an Indian survey and systems biology perspective

We aimed to survey the monogenic causes of disorders of sex development (DSD) and thereby its prevalence in India. This study revealed mutations resulting in androgen insensitivity syndrome, 5α-reductase type 2 deficiency, and gonadal dysgenesis were commonly reported. Intriguingly, AR deficits were the most prevalent (32 mutations) and of 11/26 missense mutations were in exons 4-8 (encoding ligand binding domain). The unique features of SRD5A2 defects were p.R246Q (most prevalent) and p.G196S could be mutational hotspots, dual gene defects (p.A596T in AR and p.G196S in SRD5A2) in a patient with hypospadias and novel 8 nucleotide deletion (exon 1) found in a patient with perineal hypospadias. Deficits in SRY, WT1, DHH, NR5A1, and DMRT1 caused 46,XY gonadal dysgenesis. Notably, mutations in AR, SRD5A2, MAMLD1, WT1, and MAP3K1 have led to hypospadias and only one CYP19A1 mutation caused aromatase deficiency was reported to date. Data mining from various databases has not only reinforced the role of well-established genes (e.g., SRY, WT1, DHH, NR5A1, DMRT1, AR, SRD5A2, MAMLD1) involved in DSD but also provided us 12 more potential candidate genes (ACVR1, AMHR2, CTNNB1, CYP11A1, CYP19A1, FGFR2, FGF9, PRKACA, PRKACG, SMAD9, TERT, ZFPM2), which benefit from a close association with the well-established genes involved in DSD and might be useful to screen owing to their direct gene-phenotype relationship or through direct functional interaction. As more genes have been revealed in relation to DSD, we believe ultimately it holds a better scenario for therapeutic regimen. Despite the advances in translational medicine, hospitals are yet to adopt genetic testing and counseling facilities in India that shall have potential impact on clinical diagnosis. Abbreviations: 5α-RD2: 5α-Reductase type 2; AIS: androgen insensitivity syndrome; AMH: antimullerian hormone; AMHR: antimullerian hormone receptor; AR: androgen receptor gene; CAH: congenital adrenal hyperplasia; CAIS: complete AIS; CAH: congenital adrenal hyperplasia; CHH: congenital hypogonadotropic hypogonadism; CXORF6: chromosome X open reading frame 6 gene; CYP19A1: cytochrome P450 family 19 subfamily A member 1 gene; DHT: dihydrotestosterone; DMRT1: double sex and mab-3 related transcription factor 1 gene; DSD: disorders of sexual development; GD: gonadal dysgenesis; HGMD: human gene mutation database; IH: isolated hypospadias; MAMLD1: mastermind like domain containing 1 gene; MIS: mullerian inhibiting substance; NTD: N-terminal domain; OT DSD: ovotesticular DSD; PAIS: partial AIS; SOX9: SRY-related HMG-box 9 gene; SRY: sex-determining region Y gene; STAR: steroidogenic acute regulatory protein gene; SRD5A2: steroid 5 alpha-reductase 2 gene; T DSD: testicular DSD; T: testosterone; WNT4: Wnt family member 4 gene; WT1: Wilms tumor 1 gene; Δ₄: androstenedione.

5-α-Reductase type 2 deficiency: is there a genotype-phenotype correlation? A review

5-α-Reductase type 2 enzyme catalyzes the conversion of testosterone into dihydrotestosterone, a potent androgen responsible for male sexual development during the fetal period and later during puberty. Its deficiency causes an autosomal recessive disorder of sex development characterized by a wide range of under-virilization of external genitalia in patients with a 46,XY karyotype. Mutations in the SRD5A2 gene cause 5-α-Reductase deficiency; although it is an infrequent disorder, it has been reported worldwide, with mutational heterogeneity. Furthermore, it has been proposed that there is no genotype-phenotype correlation, even in patients carrying the same mutation. The aim of this review was to perform an extensive search in various databases and to select those articles with a comprehensive genotype and phenotype description of the patients, classifying their phenotypes using the external masculinization score (EMS). Thus, it was possible to objectively compare the eventual genotype-phenotype correlation between them. The analysis showed that for most of the studied mutations no correlation can be established, although the specific location of the mutation in the protein has an effect on the severity of the phenotype. Nevertheless, even in patients carrying the same homozygous mutation, a variable phenotype was observed, suggesting that additional genetic factors might be influencing it. Due to the clinical variability of the disorder, an accurate diagnosis and adequate medical management might be difficult to carry out, as is highlighted in the review.

A study of splicing mutations in disorders of sex development

The presence of splicing sequence variants in genes responsible for sex development in humans may compromise correct biosynthesis of proteins involved in the normal development of gonads and external genitalia. In a cohort of Brazilian patients, we identified mutations in HSD17B3 and SRD5A2 which are both required for human sexual differentiation. A number of these mutations occurred within regions potentially critical for splicing regulation. Minigenes were used to validate the functional effect of mutations in both genes. We evaluated the c.277 + 2 T > G mutation in HSD17B3, and the c.544 G > A, c.548-44 T > G and c.278delG mutations in SRD5A2. We demonstrated that these mutations altered the splicing pattern of these genes. In a genomic era these results illustrate, and remind us, that sequence variants within exon-intron boundaries, which are primarily identified for diagnostic purposes and have unknown pathogenicity, need to be assessed with regards to their impact not only on protein expression, but also on mRNA splicing.

Reprint of "Steroid 5α-reductase 2 deficiency"

Dihydrotestosterone is a potent androgen metabolite formed from testosterone by action of 5α-reductase isoenzymes. Mutations in the type 2 isoenzyme cause a disorder of 46,XY sex development, termed 5α-reductase type 2 deficiency and that was described forty years ago. Many mutations in the encoding gene have been reported in different ethnic groups. In affected 46,XY individuals, female external genitalia are common, but Mullerian ducts regress, and the internal urogenital tract is male. Most affected males are raised as females, but virilization occurs at puberty, and male social sex develops thereafter with high frequency. Fertility can be achieved in some affected males with assisted reproduction techniques, and adults with male social sex report a more satisfactory sex life and quality of life as compared to affected individuals with female social sex.

Steroid 5α-reductase 2 deficiency

Dihydrotestosterone is a potent androgen metabolite formed from testosterone by action of 5α-reductase isoenzymes. Mutations in the type 2 isoenzyme cause a disorder of 46,XY sex development, termed 5α-reductase type 2 deficiency and that was described forty years ago. Many mutations in the encoding gene have been reported in different ethnic groups. In affected 46,XY individuals, female external genitalia are common, but Mullerian ducts regress, and the internal urogenital tract is male. Most affected males are raised as females, but virilization occurs at puberty, and male social sex develops thereafter with high frequency. Fertility can be achieved in some affected males with assisted reproduction techniques, and adults with male social sex report a more satisfactory sex life and quality of life as compared to affected individuals with female social sex.

Phenotype, Sex of Rearing, Gender Re-Assignment, and Response to Medical Treatment in Extended Family Members with a Novel Mutation in the SRD5A2 Gene

Deficiency of steroid 5-alpha reductase-2 (5ARD2) is an inborn error of metabolism causing a disorder of sexual differentiation. It is caused by a mutation in the SRD5A2 gene in which various mutation types have been reported. Affected individuals have a broad spectrum of presentation ranging from normal female-appearing genitalia, cliteromegaly, microphallus, hypospadias, to completely male-appearing genitalia. We report an extended Emirati family with 11 affected members. The family displayed various phenotypes on presentation leading to different sex of rearing. Some family members were reassigned gender at various stages of life. The index case was born with severe undervirilization with bilaterally palpable gonads and was raised as male from birth. He had a 46,XY karyotype and a high testosterone/dihydrotestosterone ratio. Genetic investigation revealed a novel homozygous deletion of exon 2 of the SRD5A2 gene. Both parents were found to be carriers for the gene deletion. The patient had masculinizing surgery and a course of topical dihydrotestosterone. No beneficial effect of the hormone application was noted over 3 months and the treatment was discontinued. The findings on this kindred indicate that deletion of exon 2 in the SRD5A2 gene causes various degrees of genital ambiguity leading to different sex of rearing in affected family members. Gender reassignment may be done at various ages even in conservative communities like the Gulf region.

Homozygous Ala65Pro Mutation with V89L Polymorphism in SRD5A2 Deficiency

OBJECTIVE

Deficiency of steroid 5-alpha reductase type 2 (5αRD2) is a rare autosomal recessive disorder caused by mutations in the SRD5A2 gene. A defect in the 5-alpha reductase enzyme, which ensures conversion of testosterone into dihydrotestosterone, leads to disorders of sex development. This study presents the clinical and genetic results of patients with 5αRD2 deficiency.

METHODS

5αRD2 deficiency was detected in 6 different patients from 3 unrelated families. All patients were reared as girls. Two of the patients presented with primary amenorrhea, one with primary amenorrhea and rejection of female gender, and the others with masses in their inguinal canals. Chromosome and sex-determining region Y (SRY) gene analyses were performed in all patients. Additionally, five exons of the SRD5A2 gene were amplified with polymerase chain reaction in the obtained DNA samples and evaluated.

RESULTS

While 46,XY was identified in 5 patients, 47,XXY was detected in one patient. The SRY gene was positive in all patients. The p.Ala65Pro (c193G>C) mutation and V89L polymorphism were observed in exon 1 of the SRD5A2 gene in all patients.

CONCLUSION

Identification of this mutation and polymorphism is a significant indicator of presence of 5αRD2 deficiency in Southeastern Turkey, a geographical region where consanguineous marriages are also highly common.

5α-Reductase-2 Deficiency: Clinical Findings, Endocrine Pitfalls, and Genetic Features in a Large Italian Cohort

Clinical records (n = 24) with an established diagnosis of 5α-reductase-2 deficiency were reviewed. A previous misdiagnosis was present in about 70% (period from first observation to definitive diagnosis: 9.1 ± 10.8 years), and in 8 children gonadal removal was performed before certain diagnosis. Initial sex assignment was female in 16/24 (67%) and male in 8/24 (33%) cases. After diagnosis, sex re-assignment was performed in 5 babies (4 girls to male sex; 1 boy to female sex). Baseline testosterone/DHT ratio was diagnostic in 6/12 subjects (first months of life n = 4; puberty n = 2), while post-hCG testosterone/DHT ratio was diagnostic in all tested individuals (choosing both the cut-off value 15 or 10). Eighteen different mutations in the steroid-5α-reductase-2 (SRD5A2) gene were identified, 5 of which have never been reported. In conclusion, a time lag exists before the diagnosis of 5α-reductase-2 deficiency is established; sex assignment and gonadal removal may be performed before certain diagnosis. Sex re-assignment is usually female to male, but the contrary may occur. A large variability in clinical phenotypes and genetic mutations was present in this cohort. Accurate endocrine evaluation is recommended in babies possibly affected by 5α-reductase-2 deficiency, since the use of appropriate cut-off values of testosterone/DHT ratio after hCG stimulation may permit to select individuals for SRD5A2 gene analysis. A genotype-phenotype correlation was not found in this study.

408 Cases of Genital Ambiguity Followed by Single Multidisciplinary Team during 23 Years: Etiologic Diagnosis and Sex of Rearing

Objective. To evaluate diagnosis, age of referral, karyotype, and sex of rearing of cases with disorders of sex development (DSD) with ambiguous genitalia. Methods. Retrospective study during 23 years at outpatient clinic of a referral center. Results. There were 408 cases; 250 (61.3%) were 46,XY and 124 (30.4%) 46,XX and 34 (8.3%) had sex chromosomes abnormalities. 189 (46.3%) had 46,XY testicular DSD, 105 (25.7%) 46,XX ovarian DSD, 95 (23.3%) disorders of gonadal development (DGD), and 19 (4.7%) complex malformations. The main etiology of 46,XX ovarian DSD was salt-wasting 21-hydroxylase deficiency. In 46,XX and 46,XY groups, other malformations were observed. In the DGD group, 46,XY partial gonadal dysgenesis, mixed gonadal dysgenesis, and ovotesticular DSD were more frequent. Low birth weight was observed in 42 cases of idiopathic 46,XY testicular DSD. The average age at diagnosis was 31.7 months. The final sex of rearing was male in 238 cases and female in 170. Only 6.6% (27 cases) needed sex reassignment. Conclusions. In this large DSD sample with ambiguous genitalia, the 46,XY karyotype was the most frequent; in turn, congenital adrenal hyperplasia was the most frequent etiology. Malformations associated with DSD were common in all groups and low birth weight was associated with idiopathic 46,XY testicular DSD.

Phenotype, genotype and gender identity in a large cohort of patients from India with 5α-reductase 2 deficiency

Deficiency of the 5α-reductase 2 enzyme impairs the conversion of testosterone to dihydrotestosterone (DHT) and differentiation of external genitalia, seminal vesicles and prostate in males. The present study describes the phenotype, genotype and gender identity in a large cohort of patients with 5αRD2. All patients underwent detailed clinical evaluation, hormonal profile, karyotyping and molecular analysis of the SRD5A2 gene. The molecular analysis of the SRD5A2 gene showed the presence of mutant alleles in 24 patients. We found 6 novel mutations IVS(1-2) T>C, p.A52T, 188-189insTA, 904-905ins A, p.A12T and p.E57X in our patients. All patients had ambiguous genitalia and the degrees of under-virilization ranged from penoscrotal hypospadias and microphallus to clitoromegaly. The position of gonads was variable in patients with same mutation. All the patients with mutations in the SRD5A2 gene had male gender identity. Those reared as female had gender dysphoria and underwent gender reassignment. Though a specific genotype-phenotype correlation could not be established in our patient but confirming the diagnosis of 5αRD2 with assessment of the SRD5A2 gene may help in appropriate gender assignment.

Disorders of sex development: a genetic study of patients in a multidisciplinary clinic

Sex development is a process under genetic control directing both the bi-potential gonads to become either a testis or an ovary, and the consequent differentiation of internal ducts and external genitalia. This complex series of events can be altered by a large number of genetic and non-genetic factors. Disorders of sex development (DSD) are all the medical conditions characterized by an atypical chromosomal, gonadal, or phenotypical sex. Incomplete knowledge of the genetic mechanisms involved in sex development results in a low probability of determining the molecular definition of the genetic defect in many of the patients. In this study, we describe the clinical, cytogenetic, and molecular study of 88 cases with DSD, including 29 patients with 46,XY and disorders in androgen synthesis or action, 18 with 46,XX and disorders in androgen excess, 17 with 46,XY and disorders of gonadal (testicular) development, 11 classified as 46,XX other, eight with 46,XX and disorders of gonadal (ovarian) development, and five with sex chromosome anomalies. In total, we found a genetic variant in 56 out of 88 of them, leading to the clinical classification of every patient, and we outline the different steps required for a coherent genetic testing approach. In conclusion, our results highlight the fact that each category of DSD is related to a large number of different DNA alterations, thus requiring multiple genetic studies to achieve a precise etiological diagnosis for each patient.

Phenotypic and molecular characteristics in eleven Chinese patients with 5α-reductase Type 2 deficiency

CONTEXT

Steroid 5α-reductase type 2 deficiency (5α-RD2) is a male-limited, autosomal recessive inherited disease. Affected 46, XY individuals usually present with ambiguous genitalia at birth. An early and precise diagnosis is of great value to the long-term prognosis of the disease.

OBJECTIVE

To describe the clinical features and molecular determinants in 11 Chinese patients with the SRD5A2 gene mutation and to investigate the functional alteration arising from a novel splicing site mutation identified in one of the patients.

SUBJECTS AND METHODS

Eleven subjects born with abnormal external genitalia from 10 unrelated families were recruited. Among them, nine patients who were reared as girls underwent virilization and gender change after puberty. Genotyping analysis of the SRD5A2 gene was performed in each of the patients. Haplotype analysis was performed in five patients with a prevalent mutation of p.G203S to illustrate the founder effect in China. Functional impairment of the new variant was explored by an in vitro splicing study and enzymatic activity assay.

RESULTS

Nine mutations in the SRD5A2 gene were detected in the eleven patients. In addition to the previously reported p.G203S, p.R227Q, p.N193S, p.R246Q, p.Q6X, p.A228V, c.655delT and IVS1-2 A>G, a novel splicing site mutation (IVS4 + 2 T>C) was identified. From an in vitro functional study, this mutation was found to result in a skipping of exon 4 in the course of mRNA splicing, leading to a truncated protein of 205 amino acids that lacks the catalysing activity. Two siblings with the same compound heterozygous mutation (IVS1-2A>G/p.G203S) exhibited differing phenotypes and opposite patterns of gender rearing. A prevalent variation p.V89L combined with c.655delT was revealed to cause a mild phenotype of 5α-RD2 with a micropenis.

CONCLUSION

This cohort study describes the phenotypic, biochemical and long-term outcome in 11 Chinese patients with 5α-RD2 deficiency and defines the genotypic spectrum of SRD5A2 mutations in China.

Novel nucleotide insertions in two unrelated Indian patients with 5α reductase 2 deficiency leading to premature termination of SRD5A2 enzyme

T is converted to a more potent androgen, DHT by the action of microsomal membrane enzyme 5α reductase 2. Defects in 5α reductase 2 isozyme results in incomplete virilisation of external male genitalia. Mutations in SRD5A2 gene leads to diminished enzyme activity, thus hampering DHT synthesis from T. We describe two unrelated patients from India with 5αRD2 due to novel insertion of nucleotides in the exon 1 of SRD5A2 gene that lead to premature termination of protein. Master S (case 1; III.8) was 3 years old at initial evaluation, had perineoscrotal hypospadias, microphallus and both testes were palpable in the inguinal region. Master P (case 2; III.9) was born as normal full term baby. He had primary complaint of microphallus, penoscrotal hypospadias and gonads in the inguinal region. Diagnosis of 5αRD2 was made, as T/DHT ratio in the two cases was 41 and 131.2 respectively. Sequence analysis of SRD5A2 gene showed an insertion of nucleotides TA in exon 1 (c.188_189). This resulted in premature termination of the protein due to stop codon at amino acid position 7. The protein formed is drastically truncated and inadequate protein synthesized explains the phenotypic characteristics of our patients.

Diagnosis of 5α-Reductase 2 Deficiency: Is Measurement of Dihydrotestosterone Essential?

BACKGROUND

5α-Reductase 2 deficiency (5ARD) is a known cause of 46,XY disorders of sex development (DSD). Traditionally, the diagnosis relies on dihydrotestosterone (DHT) measurement, but the results are often equivocal, potentially leading to misdiagnosis. We reviewed alternative approaches for diagnosis of 5ARD.

METHODS

We conducted a retrospective review of the results of urinary steroid profiling (USP) by GC-MS and mutational analysis of SRD5A2 [steroid-5-alpha-reductase, alpha polypeptide 2 (3-oxo-5 alpha-steroid delta 4-dehydrogenase alpha 2)] by PCR and direct DNA sequencing of all 46,XY DSD patients referred to our laboratory with biochemical and/or genetic findings compatible with 5ARD. We also performed a literature review on the laboratory findings of all 5ARD cases reported in the past 10 years.

RESULTS

Of 16 patients diagnosed with 5ARD between January 2003 and July 2012, 15 underwent USP, and all showed characteristically low 5α- to 5β-reduced steroid metabolite ratios. Four patients had DHT measured, but 2 did not reach the diagnostic cutoff. In all 12 patients who underwent genetic analysis, 2 mutations of the SRD5A2 gene were detected to confirm the diagnosis. Twenty-four publications involving 149 patients with 5ARD were published in the review period. Fewer than half of these patients had DHT tested. Nearly 95% of them had the diagnosis confirmed genetically.

CONCLUSIONS

5ARD can be confidently diagnosed by USP at 3 months postnatally and confirmed by mutational analysis of SRD5A2. Interpretation of DHT results may be problematic and is not essential in the diagnosis of 5ARD. We propose new diagnostic algorithms for 46,XY DSD.

Clinical biochemistry of dihydrotestosterone

Dihydrotestosterone (DHT) is the most potent natural androgen in humans. There has been an increasing interest in this androgen and its role in the development of primary and secondary sexual characteristics as well as its potential roles in diseases ranging from prostate and breast cancer to Alzheimer's disease. Despite the range of pathologies shown to involve DHT there is little evidence for measurement of serum DHT in the management of these diseases. In this review we describe the physiology of DHT production and action, summarize current concepts in the role of DHT in the pathogenesis of various disorders of sexual development, compare current methods for the measurement of DHT and conclude on the clinical utility of DHT measurement. The clinical indications for the measurement of DHT in serum are: investigation of 5α reductase deficiency in infants with ambiguous genitalia and palpable gonads; men with delayed puberty and/or undescended testes; and to confirm the presence of active testicular tissue. Investigation is aided by the use of human chorionic gonadotrophin stimulation. Due to paucity of published data on this procedure, it is important to follow guidelines prescribed by the laboratory performing the analysis to ensure accurate interpretation.

Molecular diagnosis of 5α-reductase type II deficiency in Brazilian siblings with 46,XY disorder of sex development

The steroid 5α-reductase type II enzyme catalyzes the conversion of testosterone (T) to dihydrotestosterone (DHT), and its deficiency leads to undervirilization in 46,XY individuals, due to an impairment of this conversion in genital tissues. Molecular analysis in the steroid 5α-reductase type II gene (SRD5A2) was performed in two 46,XY female siblings. SRD5A2 gene sequencing revealed that the patients were homozygous for p.Gln126Arg missense mutation, which results from the CGA > CAA nucleotide substitution. The molecular result confirmed clinical diagnosis of 46,XY disorder of sex development (DSD) for the older sister and directed the investigation to other family members. Studies on SRD5A2 protein structure showed severe changes at NADPH binding region indicating that structural modeling analysis can be useful to evaluate the deleterious role of a mutation as causing 5α-reductase type II enzyme deficiency.

Mutation prediction by PolyPhen or functional assay, a detailed comparison of CYP27B1 missense mutations

Vitamin D-dependent rickets type 1 (VDDR-I) is caused by mutation in CYP27B1. The glycine residue at codon 102 is not conserved between human (G(102)) and rodent (S(102)). G102E mutation results in 80% reduction in its enzymatic activity but PolyPhen predicts benign change. It is not known whether G102S has any damaging effect on 1α-hydroxylase activity. We investigated the effect of CYP27B1 (G102S) on its enzymatic activity and compared mutation prediction accuracy for all known CYP27B1 mutations among three free online protein prediction programs: PolyPhen, PolyPhen-2, and PSIPRED. G102S has no damaging effect on 1α-hydroxylase activity. G102D retained 30% enzymatic activity. All three programs correctly predicted damaging change for G102D. PolyPhen predicted benign change for G102S, whereas PolyPhen-2 and PSIPRED indicated possible damaging effect. Among 24 reported damaging mutations, PSIPRED, PolyPhen-2, and PolyPhen achieved 100%, 91.7% (22/24), and 75% (18/24) accuracy rate, respectively. The residues of incorrectly predicted mutations were not conserved. We conclude that G102D resulted in a significant reduction in 1α-hydroxylase activity, whereas G102S did not. PSIPRED and PolyPhen-2 are superior to PolyPhen in predicting damaging mutations.

SRD5A2 gene mutations and polymorphisms in Spanish 46,XY patients with a disorder of sex differentiation

One hundred and forty-six index patients with 46,XY DSD in whom gonads were confirmed as testes were consecutively studied for a molecular diagnosis during the period 2002-2010. AR gene was analysed in all patients as the first candidate gene, yielding a mutation in 42.5% of cases and SRD5A2 gene was analysed as the second candidate gene, resulting in the characterization of 10 different mutations (p.Y91D, p.G115D, p.Q126R, p.R171S, p.Y188CfsX9, p.N193S, p.A207D, p.F219SfsX60, p.R227Q and p.R246W) in nine index patients (6.2% of the total number of 46,XY DSD patients). One of the mutations (p.Y188CfsX9) has never been reported. In addition, we genotyped SRD5A2 gene p.V89L and c.281+15T>C polymorphisms in 46,XY DSD and in 156 normal adult males and found that patients with SRD5A2 mutations or without a known molecular diagnosis presented a higher frequency of homozygous p.L89, homozygous TT and combined CCTT genotypes compared with controls. This result suggests that 46,XY DSD patient phenotypes may be influenced by SRD5A2 polymorphism genotypes. SRD5A2 gene mutations may not be as infrequent as previously considered in 46,XY DSD patients with variable degrees of external genitalia virilization at birth and normal T production and appears to be the second aetiology in our series.

A novel mutation of 5alpha-steroid reductase 2 deficiency (CD 65 ALA-PRO) with severe virilization defect in a Turkish family and difficulty in gender assignment

Molecular genetic characterization of mutations in SRD5A2 gene is used as an essential procedure for the final diagnosis of 5alpha-reductase deficiency. Here, we report a novel homozygous point mutation of SRD5A2 gene at codon 65 in exon 1, due to a proline for alanine substitution in a Turkish family whose proband has severe undervirilization. This mutation has not been reported up to date in association with 5alpha-reductase deficiency in various ethnic groups. We discussed some questions about gender assignment in addition to the molecular and clinical characteristics of the disease.

Molecular diagnosis of 46,XY DSD and identification of a novel 8 nucleotide deletion in exon 1 of the SRD5A2 gene

Phenotypic presentation of 46,XY DSD depends on the underlying defects. Defect in androgen action on the target tissues or production of active metabolite share common morphological features. Molecular study may help differentiating these abnormalities with precision. Mutational analysis of androgen receptor (AR) and SRD5A2 genes was performed in 29 patients with 46,XY DSD, by PCR-SSCP. The amplicons that showed an aberrant migration in SSCP were subjected to sequencing. Interestingly, six patients from 4 unrelated families (a pair of sibs, uncle/nephew and other two isolated) were identified with mutations in SRD5A2 gene. In five patients p.R246Q missense mutation was detected, of which four were homozygous and one was compound heterozygous: g.80_87delT CGCGAAG (p.A27fsX132) and p.R246Q. Another patient with isolated micropenis harbored a heterozygous p.G196S missense mutation. No AR gene mutation was detected. In conclusion, our study suggests that p.R246Q mutation is common amongst patients with SRD5A2 gene defect from the Northern states of India. Also, it records a novel deletion in exon 1 of SRD5A2 gene in a patient with severe hypospadias.

Genetic analysis of the SRD5A2 gene in Indian patients with 5alpha-reductase deficiency

BACKGROUND

5alpha-Reductase deficiency (5RD) is an uncommon autosomal recessive disorder of sexual differentiation. It results from impaired conversion of testosterone to dihydrotestosterone due to mutations in the steroid 5alpha-reductase type 2 gene (SRD5A2). Mutations in SRD5A2 have not been previously reported in Indian patients with 5RD.

AIM

To delineate the clinical features and mutations in the SRD5A2 gene in Indian patients with 5RD.

PATIENTS AND METHODS

The SRDSA2 gene was sequenced in two unrelated patients with elevated testosterone/dihydrotestosterone ratio and in one patient with classical clinical features and virilization at puberty (in whom the ratio could not be measured due to prior gonadectomy). The prevalence of SRD5A2 mutations was also studied in 52 healthy ethnic control subjects by PCR-RFLP.

RESULTS

Two patients, both from the north Indian state of Uttar Pradesh, carried the homozygous missense mutation p.R246Q in exon 5. Parents of both probands were heterozygous for the mutation. The mutation was absent in 52 control subjects. The third patient, with severe perineoscrotal hypospadias and micropenis, was detected to have a novel heterozygous missense mutation p.Q56H, as well as the homozygous polymorphism p.V89L, both in exon 1. The p.Q56H mutation was absent in 52 control subjects.

CONCLUSION

p.R246Q is a common SRD5A2 mutation in 5RD patients from the Indian subcontinent.

Identification of mutations in the SRD5A2 gene in Thai patients with male pseudohermaphroditism

OBJECTIVE

To describe two unrelated Thai patients with suspected 5alpha-reductase type 2 deficiency and perform mutation analysis of the SRD5A2 gene.

DESIGN

Case report.

SETTING

A pediatric endocrinology clinic at a university hospital.

PATIENT(S)

Two unrelated patients with 46,XY karyotype, born with ambiguous genitalia, were studied. One was reared as a boy and the other was reared as a girl.

INTERVENTION(S)

The entire coding regions of the SRD5A2 gene were assessed by polymerase chain reaction (PCR) and sequencing analysis.

MAIN OUTCOME MEASURE(S)

Molecular characterization of the SRD5A2 gene.

RESULT(S)

Four different pathogenic mutations (three missense and one nonsense) were identified. These were located at exon 1 (p.Q6X and p.L20P), exon 3 (p.G183S), and exon 4 (p.G203S). The T>C transition (c.59T>C) resulting in a leucine-to-proline substitution at codon 20 (p.L20P) has not been previously described and was not detected in 100 unaffected, ethnic-matched control chromosomes. In addition, p.G183S, previously identified only among patients from mixed African-European ancestry and in the Dominican Republic, was also detected in a Thai patient.

CONCLUSION(S)

This study demonstrates that the SRD5A2 gene is responsible for 5alpha-reductase type 2 deficiency across different populations and emphasizes the important role of genetic testing for the definite diagnosis and genetic counseling before gender assignment or any surgical intervention.

Effects of various pesticides on human 5α-reductase activity in prostate and LNCaP cells

Certain pesticides are able to disturb the sex steroid hormone system and to act as antiandrogens. While the different underlying mechanisms remain unclear, inhibition of 5alpha-reductase, the enzyme which is indispensable for the synthesis of DHT and thus normal masculinization, appears to be one of the sensitive targets for endocrine disruption. We therefore tested several endocrine disrupters with antiandrogenic effects in vivo for their influence on 5alpha-reductase activity in two different test systems: (a) an enzyme assay with human Lymph Node Carcinoma of Prostate (LNCaP) cells and (b) an enzyme assay with human prostate tissue homogenate. The selected pesticides and industrial compounds were monobutyltin (MBT), dibutyltin (DBT), tributyltin (TBT), triphenyltin (TPT), diuron, fenarimol, linuron, p,p'DDE, prochloraz and vinclozolin. The synthetic androgen methyltestosterone and the synthetic antiandrogen flutamide, as well as the 5alpha-reductase inhibitor finasteride served as control compounds. The effect of the organotin compounds DBT, TBT and TPT on enzyme activity was approximately the same in both test systems, with IC(50) values ranging between 2.7 and 11.2 microM, while in prostate tissue, methyltestosterone and prochloraz proved to be stronger inhibitors (IC(50) values of 1.9 and 12.4 microM) than in LNCaP cells (IC(50) values of 13.2 and 53.2 microM). The inhibitory impact of finasteride was approximately 130 times stronger in prostate tissue than in LNCaP cells. Fenarimol, flutamide, linuron and p,p'DDE inhibited 5alpha-reductase activity only at very high concentrations (IC(50)> or =24 microM) in prostate homogenates, and not at all in LNCaP cells. On average, the IC(20) values were 3.5 times lower than the IC(50) values. Diuron, MBT and vinclozolin exerted no effect in either of the test systems. The finding of pesticides acting as 5alpha-reductase inhibitors might be of clinical relevance. As a screening tool for putative ED, the tissue assay is the more practical and sensitive method. However, the cell assay can, to some extent, reflect particular cell processes since the living cell is able to compensate moderate toxicological effects of the ED on cell viability, and possibly also their impact on 5alpha-reductase activity.