Recent advances in hypospadias: current surgical technique and research in incidence and etiology

Association between CACNA1D polymorphisms and hypospadias in a southern Chinese population

BACKGROUND

Hypospadias is a congenital genitourinary malformation, with the etiology remaining complex and poorly understood. Despite several genes have been identified to be associated with the risk of hypospadias, current understanding of the susceptibility loci for hypospadias yet remained largely improved. The CACNA1D gene encodes calcium voltage-gated channel subunit alpha 1d and may be involved in androgen signaling. However, the genetic susceptibility of CACNA1D associated with hypospadias has yet been addressed.

OBJECTIVE

To evaluate the association between CACNA1D polymorphisms and the susceptibility to hypospadias.

METHODS

In this study, we accessed the association between two potential regulatory SNPs (rs3774491 and rs898415) within CACNA1D and hypospadias in a cohort of southern Chinese population which comprised of 740 cases and 948 healthy individuals. Both SNP and haplotypic associations were evaluated. Bioinformatic analysis of the regulatory abilities of the CACNA1D SNPs were carried out by utilizing public ChIP-seq and DNase-seq data. The expression of Cacna1d in mouse external genitalia and testis was evaluated by qPCR.

RESULTS

We found that the allele C in rs3774491 and allele G in rs898415 were significantly associated with an increased risk of hypospadias, especially for proximal hypospadias. Further model-based genotypic analyses showed that these association were prominent in additive model and recessive models. Bioinformatic analyses indicated that both SNPs were colocalized with DNase and multiple histone marker across multiple tissues, suggesting the regulatory potentials for these variants. Cacna1d is detectable in both testis and external genitalia of mouse, but the expression level was more prominent in testis than that in external genitalia, suggesting tissue-specific differences in its expression.

CONCLUSION

Our findings provide evidence for CACNA1D as a novel predisposing gene for hypospadias, shedding new light on the genetic basis of malformation of urinary tract. Further investigations are warranted to elucidate the functional implication of CACNA1D underlying the development of hypospadias.

LEVEL OF EVIDENCE

N/A.

Hypospadias in the neonate

Hypospadias is a common developmental disorder of the urogenital tract, occurring in approximately 1 in 125 live male births. Defined as an atypical urethral opening anywhere along the shaft of the penis, scrotum, or perineum, hypospadias is often associated with a deficient prepuce and chordee. Hypospadias usually occurs as an isolated defect, but can be part of a recognized syndrome or associated with other genital anomalies. The etiology of nonsyndromic hypospadias is unknown, and is believed to be multifactorial. Recent studies have implicated factors such as familial inheritance, low birth weight, assisted reproductive technology, advanced maternal age, paternal subfertility, and endocrine-disrupting chemicals in the pathogenesis of hypospadias. Infants with hypospadias should not undergo circumcision. Currently, most infants with hypospadias undergo surgical reconstruction between 4 and 8 months of age. Parents of a newborn with hypospadias may be anxious and have many questions about their infant's condition. They should be given the opportunity to speak to a pediatric urologist as early as possible. This article provides a guide to the embryologic origins of hypospadias and a photographic atlas to aid bedside clinicians in identifying the spectrum of hypospadias in the newborn.