Identification of three novel SRD5A2 mutations in Chinese patients with 5α-reductase 2 deficiency

In vitro functional study of fifteen SRD5A2 variants found in Chinese patients and the relation between the SRD5A2 genotypes and phenotypes

The 5α-reductase type 2 (5α-RD2) deficiency is one of the most common etiology of 46, XY disorders of sex development and is caused by pathogenic variants in SRD5A2. Massively parallel sequencing contributes to identification of numerous novel SRD5A2 variants, in vitro functional study could help to determine their pathogenicity. In this study, we aim to present the functional study of fifteen SRD5A2 variants found in Chinese patients and explore the genotype-phenotype association. We collected the clinical manifestation and genotype of 38 patients with 5α-RD2 deficiency who visited our center between 2009 and 2021. The pathogenicity of seven missense SRD5A2 variants, were predicted by in-silico tools. Furthermore, fifteen SRD5A2 variants without reported functional assay were studied in vitro to analyze the role of these variants in enzymatic activity. Twenty-four SRD5A2 rare variants were identified in 38 patients with 5α-RD2 deficiency. Fifteen variants without reported functional assay decreased the conversation of testosterone (T) to dihydrotestosterone(DHT) and caused the almost complete loss of enzyme activity (<8 %) in our in-vitro functional study. Thirty-eight patients with three different external genital phenotypes (complete female, clitoromegaly and hypospadias) were found to have same variants. Patients with different testicular position (scrotum/clitoris and cryptorchidism) were found to have same variants. Our study showed 15 SRD5A2 variants caused complete loss of 5α-RD2 enzyme activity by functional study. Patients with different clinical phenotypes can have the same genotypes and no obvious genotype-phenotype association exist in our series patients.

The Genotype-Phenotype Correlation in Human 5α-Reductase Type 2 Deficiency: Classified and Analyzed from a SRD5A2 Structural Perspective

The phenotype of the 5α-reductase type 2 deficiency (5αRD2) by the SRD5A2 gene mutation varies, and although there have been many attempts, the genotype-phenotype correlation still has not yet been adequately evaluated. Recently, the crystal structure of the 5α-reductase type 2 isozyme (SRD5A2) has been determined. Therefore, the present study retrospectively evaluated the genotype-phenotype correlation from a structural perspective in 19 Korean patients with 5αRD2. Additionally, variants were classified according to structural categories, and phenotypic severity was compared with previously published data. The p.R227Q variant, which belongs to the NADPH-binding residue mutation category, exhibited a more masculine phenotype (higher external masculinization score) than other variants. Furthermore, compound heterozygous mutations with p.R227Q mitigated phenotypic severity. Similarly, other mutations in this category showed mild to moderate phenotypes. Conversely, the variants categorized as structure-destabilizing and small to bulky residue mutations showed moderate to severe phenotypes, and those categorized as catalytic site and helix-breaking mutations exhibited severe phenotypes. Therefore, the SRD5A2 structural approach suggested that a genotype-phenotype correlation does exist in 5αRD2. Furthermore, the categorization of SRD5A2 gene variants according to the SRD5A2 structure facilitates the prediction of the severity of 5αRD2 and the management and genetic counseling of patients affected by it.

Lessons from 17β-HSD3 deficiency: Clinical spectrum and complex molecular basis in Chinese patients

17β-Hydroxysteroid dehydrogenase type 3 (17β-HSD3) deficiency is rarely reported in Chinese patients with 46, XY disorders of sexual development (DSD). Seven subjects with 17β-HSD3 deficiency were identified from 206 Chinese 46, XY DSD patients using targeted next-generation sequencing (NGS). Serum AD and T levels were measured by liquid chromatography-tandem mass spectrometry (LC-MS/MS). In silico and functional studies were performed to evaluate the enzymatic activity impairment of HSD17B3 variants. A minigene assay was performed in an exonic splicing variant. Our results showed that four novel and five reported HSD17B3 variants were identified in 7 unrelated patients. The patients showed cryptic presentation during childhood and classical virilization after puberty with T/AD ratio< 0.4. A heterozygous large deletion from the 5'UTR to exon 1 was identified in a patient with a monoallelic variant of p.N130S. Although predicted to be 'likely pathogenic', only p. S232P and p. S160F drastically reduced the enzymatic activity of 17β-HSD3. A previously reported 'missense' variant c 0.277 G>A (p. E93K) was revealed to have no impact on enzyme activity but resulted in aberrant splicing of exon 3 and was reclassified as an exonic splicing variant. In our study, one nonsense, one exonic splicing, one deletion, one large deletion and five missense variants were detected in patients with 17β-HSD3 deficiency, expanding the clinical and molecular profile of this disorder. In silico analysis should be cautiously interpreted when the heredity pattern and functional study are inconsistent.

An Extremely Rare SRD5A2 Gene c.485A>C Mutation in a Compound Heterozygous Newborn with Disorders of Sex Development First Identified in Vietnam

SRD5A2 (steroid 5-alpha-reductase 2) mutation, which impairs 5α-reductase-2 enzyme activity, is among the causes of 46,XY disorders of sex development (DSD). Here, we report a rare pathogenic mutation NM_000348.4:c.485A>C (NP_000339.2:p.His162Pro) of SRD5A2 gene in a compound heterozygous state first identified in a Vietnamese newborn with 5α-reductase-2 enzyme deficiency. We also first submitted this rare mutation to ClinVar database (VCV000973099.1). The patient presented with hyperpigmented labia-majora-like bifid scrotum, clitoris-like phallus, perineoscrotal hypospadias, and blind-ending vagina. The other mutation NM_000348.4:c.680G>A (NP_000339.2:p.Arg227Gln) was reported previously. This compound heterozygous mutation was first detected by next-generation sequencing. By Sanger sequencing, we confirmed that the c.485A>C mutation was maternal inherited, whereas the c.680G>A mutation was paternal inherited. Up to date, this is the first report of this rare compound heterozygous state of SRD5A2 c.485A>C and c.680G>A mutations in patients with 46,XY DSD generally as well as in Vietnamese population particularly and is also the second report in the world carrying the pathogenic mutation NM_000348.4:c.485A>C (NP_000339.2:p.His162Pro). Our finding has enriched the understanding of the spectrum of SRD5A2 variants and phenotypic correlation in Asian patients with 46,XY DSD.

Differences of adrenal-derived androgens in 5α-reductase deficiency versus androgen insensitivity syndrome

Steroid 5α‐reductase type 2 deficiency (5α‐RD2) and androgen insensitivity syndrome (AIS) are difficult to distinguish clinically and biochemically, and adrenal‐derived androgens have not been investigated in these conditions using modern methods. The objective of the study was to compare Chinese patients with 5α‐RD2, AIS, and healthy men. Sixteen patients with 5α‐RD2, 10 patients with AIS, and 39 healthy men were included. Serum androgen profiles were compared in these subjects using liquid chromatography/tandem mass spectrometry (LC‐MS/MS). Based on clinical features and laboratory tests, 5α‐RD2 and AIS were diagnosed and confirmed by genotyping. Dihydrotestosterone (DHT) and testosterone (T) were both significantly lower in patients with 5α‐RD2 than AIS (p < 0.0001). The T/DHT ratio was higher in 5α‐RD2 (4.5–88.6) than AIS (13.4–26.7) or healthy men (7.6–40.5). Using LC‐MS/MS, a cutoff T/DHT value of 27.3 correctly diagnosed 5α‐RD2 versus AIS with sensitivity 93.8% and specificity 100%. Among the adrenal‐derived 11‐oxygenated androgens, 11β‐hydroxyandrostenedione (11OHA4) and 11‐ketoandrostenedione (11KA4) were also lower in patients with 5α‐RD2 than those of patients with AIS. In contrast, 11β‐hydroxytestosterone (11OHT) was higher in 5α‐RD2 than AIS. Furthermore, a 11OHT/11OHA4 cutoff value of 0.048 could also distinguish 5α‐RD2 from AIS. Thus, both elevated T/DHT values above 27.3 and the unexpected 11‐oxygenated androgen profile, with a 11OHT/11OHA4 ratio greater than 0.048, distinguished 5α‐RD2 from AIS. These data suggest that the metabolism of both gonadal and adrenal‐derived androgens is altered in 5α‐RD2.

A novel SRD5A2 mutation in an Iranian family with sex development disorder

Disorders of sex development (DSD) are different types of conditions that their accurate diagnosis by using conventional phenotypic and biochemical approaches is a challenging issue. Precise determination of DSD is critical due to the detection of possible life-threatening associated disorders. It may also assist parents in choosing the most suitable management for their affected child. In this study, two affected kids born from consanguineous families who were clinically diagnosed for sex development disorder were investigated for the main cause of the disease. Biochemical analysis failed to make an accurate diagnosis. Karyotype analysis showed an abnormal sex chromosome pattern. Whole exome sequencing was sequentially applied to precisely ascertain the genetic cause of the disease. A novel deletion, g.40936_53878del12943insTG (NG_008365.1), and one known mutation, c.586G>A (p.Gly196Ser), were detected in SRD5A2 gene in case I and case II respectively. Further analysis was performed using polymerase chain reaction, primer walking and Sanger sequencing to detect the nucleotides changes accurately. Segregation analysis in the families confirmed 13kb novel homozygous deletion of SRD5A2 in case I and c.586G>A in case II. The present study confirms the diagnostic value of whole exome sequencing in the detection of DSD aetiology, especially when several differential diagnoses are possible.

Genetic Analysis of 25 Patients with 5α-Reductase Deficiency in Chinese Population

Background

A deficiency in steroid 5α-reductase type 2 is an autosomal recessive disorder. Affected individuals manifested ambiguous genitalia, which is caused by decreased dihydrotestosterone (DHT) synthesis in the fetus.

Methods

We analyzed 25 patients with 5α-reductase deficiency in China. Seventeen of the 25 patients (68%) were initially raised as females. Sixteen patients changed their social gender from female to male after puberty.

Results

Eighteen mutations were identified in these patients. p.Gly203Ser and p.Gln6∗ were found to be the most prevalent mutations. On the basis of the genotype of these patients, we divided them into different groups. There was no significant difference in hormone levels and external masculinization score (EMS) in patients with or without these prevalent mutations. Twelve common single-nucleotide polymorphisms (SNPs) near the p.Gln6∗ mutation were chosen for haplotype analysis. Three haplotypes were observed in 6 patients who had the p.Gln6∗ mutation (12 alleles).

Conclusion

We analyzed mutations of the SRD5A2 gene in Chinese patients with 5α-reductase deficiency. Although hotspot mutations exist, no founder effect of prevalent mutations in the SRD5A2 gene was detected in the Chinese population.

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.