Mutation analysis of the SRD5A2, AR and SF-1 genes in 52 Chinese boys with 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.

Identification of gene variants in 130 Han Chinese patients with hypospadias by targeted next-generation sequencing

Background

Hypospadias is a common congenital malformation of male external genitalia, which mainly manifests as an abnormal urethral opening on the ventral side of the penis. The etiology and clinical phenotype of hypospadias is highly heterogeneous, and its clinical diagnosis is challenging. Currently, over 70% of patients have an unknown etiology. Here, we performed a targeted analysis of gene mutations in 130 patients with hypospadias of unknown etiology to find the precise genetic cause.

Methods

We developed a targeted next‐generation sequencing (NGS) panel, encompassing the exon coding regions of 105 genes involved in external genitalia and urogenital tract development and performed sequencing analysis on 130 children with hypospadias of unknown etiology.

Results

In total, 25 patients with hypospadias (19.2%) were found to have 20 mutations among the nine genes involved in external genitalia and urogenital tract development, including 16 reported and four novel mutation sites. Twenty‐two patients (16.9%) had diagnostic variants. Multiple genetic mutations were identified in three of the 25 patients. Hypospadias combined with micropenis was the most common phenotype (68%) in 25 patients.

Conclusions

Higher frequency mutations were identified in SRD5A2 (52%) and AR (24%) in our patient cohort. Middle or posterior hypospadias with micropenis may be significant indicators of genetic variations. Polygenic inheritance may be a rare genetic cause of hypospadias.

Genetic Polymorphism in the RYR1 C6487T Is Associated with Severity of Hypospadias in Chinese Han Children

Objective

Hypospadias is a common congenital malformation of the male external genitalia. Most cases have an unknown etiology, which is probably a mix of monogenic and multifactorial forms, implicating both genetic and environmental factors. Ryanodine receptor 1 (RYR1) mutations are a common cause of congenital diseases associated with both dominant and recessive inheritance in humans. Herein, we evaluated the correlations of RYR1 C6487T polymorphism with the risk and severity of hypospadias.

Methods

263 congenital hypospadias children and 312 healthy children were recruited. The polymorphism of RYR1 C6487T in the peripheral blood was detected by polymerase chain reaction-restriction fragment length polymorphism, and different genotypes and allelic genes were analyzed to explore their associations with the risk of congenital hypospadias.

Results

The distribution frequencies of CC/CT/TT genotypes and two alleles (C and T) at RYR1 C6487T showed significant differences between the case and control groups (P < 0.05). The frequency of C allele in the case and control groups was 46.95% and 54.94%, respectively, and of T allele was 53.05% and 45.06% (P < 0.05). In addition, the distribution frequency of CC/CT/TT genotypes exhibited significant difference between patients with mild hypospadias and those with moderate or severe hypospadias (all P > 0.05), suggesting that RYR1 C6487T polymorphism is correlated with the severity of congenital hypospadias (X² = 13.722, P = 0.001).

Conclusion

Our study demonstrated that RYR1 C6487T polymorphism might be associated with an increased risk of congenital hypospadias in Chinese Han children. Our findings highlight the heterogeneous nature of hypospadias genetic susceptibility.

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.