Molecular genetics and phenotype/genotype correlation of 5-α reductase deficiency in a highly consanguineous population

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.

Effects of Androgen Treatment on Growth in Patients with 5-α-Reductase Type 2 Deficiency

BACKGROUND

Patients with 5-α-reductase type 2 deficiency (5αRD2) require androgen treatment for the growth of normal male external genitalia. Since limited research has been conducted on the effects of androgen treatment on height in individuals with 5αRD2, we investigated the effect of androgen treatment on bone age (BA) and the height status in children with 5αRD2.

METHODS

Of the 19 participants who were followed up for an average of 10.6 years, 12 received androgen treatment. BA and height standard deviation scores (SDS) were compared between the treatment and non-treatment groups, as well as between the dihydrotestosterone (DHT) and testosterone enanthate (TE) treatment groups.

RESULTS

Despite the above-average height of the 19 patients with 5αRD2, the height SDS relative to BA (htSDS-BA) was below average, particularly in the androgen treatment group. DHT treatment did not lead to an increase in BA or htSDS-BA, whereas TE treatment resulted in BA advancement and decreased htSDS-BA, especially in the prepubertal period.

CONCLUSIONS

DHT treatment is more favorable for height than TE treatment in patients with 5αRD2, particularly during the prepubertal period. Therefore, age and the type of androgen used should be carefully considered to minimize the risk of height reduction in these patient groups.

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.

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.

Novel Deleterious Mutation in Steroid-5α-Reductase-2 in 46, XY Disorders of Sex Development: Case Report Study

Background: Steroid-5α-reductase-2 (SRD5A2) and 17β-hydroxysteroid dehydrogenase type 3 (17β-HSD3) enzyme deficiencies are frequent causes of 46, XY disorder of sex development (46, XY DSD), where an infant with 46, XY has a female phenotype. We assessed the hydroxy-steroid-17β-dehydrogenase-3 (HSD17B3)and SRD5A2 genes in twenty Iranian phenotypic females with 46,XY DSD. Materials and methods: All exons in HSD17B3 and SRD5A2 genes were subjected to PCR amplification followed by sequencing. Results: Of 20 identified 46, XY DSD patients, one had a homozygous missense 17β-HSD3 mutation Ser65Leu (c.194C > T). We found 1 SRD5A2 novel homozygous missense mutation of Tyr242Asp (c.891T > G) in exon 5, which in-silico analyses revealed that this mutation may have deleterious impact on ligand binding site of SRD5A2 protein. Three other individuals harbored 17β-HSD3 deficiencies without identified mutations. Conclusions: SRD5A2 and 17β-HSD3 mutations are found in 10% of 46, XY DSD Iranian patients.

Molecular genetics of disorders of sex development in a highly consanguineous population

Consanguinity increases the risk of hereditary diseases including disorders of sex development (DSD). There are minimal data on DSD in the highly consanguineous population of Saudi Arabia. This study reports the molecular genetics of a series of patients with different types of DSD.

METHODS

We enrolled 77 patients from 47 families with DSD. DNA was isolated from peripheral leucocytes. Genes of interest were amplified by polymerase chain reaction and subsequently sequenced.

RESULTS

Overall, 77 patients from 47 families (44 of them are consanguineous) had a total of 29 mutations; 16 of them were described before and 13 were novel mutations. The most common condition was 5-α reductase (SRD5A2) deficiency (25 patients from 18 families) and the most common mutation was a splice site mutation in intron 1 (c.282-2A>G). The next most common condition was 11-β hydroxylase (CYP11B1) deficiency where 19 patients from 10 families had 8 mutations (7 of them are novel). Other mutations affected CYP17A1 with 2 novel and 2 known mutations in 7 patients; HSD3B2 with 2 known mutations in 11 patients of 4 families; StAR with 1 novel and 1 known mutations in 4 patients; NR0B1 with 1 novel mutation in 2 siblings; HSD17B3 with 1 known mutation in 3 siblings; LHCGR with 1 novel mutation in 2 siblings; and AR with 1 novel and 3 known mutations in 4 unrelated patients.

CONCLUSION

In the highly consanguineous and homogeneous population of Saudi Arabia, SRD5A2 and CYP11B1 deficiencies are common causes of DSDs. Other DSDs occur less frequently but often with novel mutations.

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.