Mutations of Cxorf6 Cause a Range of Severities of Hypospadias

Abstract

PURPOSE Mutations in CXorf6, a recently-described candidate gene involved in the development of male genitalia, have been found in patients with 46, XY disorders-of-sexual-development (46, XY DSD) and severe hypospadias. To date, there has been no data regarding CXorf6 in isolated hypospadias without DSD. This study aimed to characterize the potential role of CXorf6 in such patients. MATERIAL AND METHODS Forty-one patients with isolated hypospadias of various severity, and 30 controls were included. DNA was extracted from excess foreskin collected during surgery. Direct sequencing for coding exons 3-6 of CXorf6 and their flanking splice sites was performed. Secondary and tertiary structures of the protein were predicted using NNpredict and PHYRE engines. RESULTS Four mutations (9.7%) were identified. One missense mutation (V432A) and two deletions (del324G, predicted to cause a stop codon L121X) occurred in patients with penoscrotal and proximal hypospadias. One patient with subcoronal hypospadias had a CAG repeat amplification in the second polyglutamine domain of CXorf6. Secondary structure prediction indicated that this insertion occurred in a helix element of the protein. The tertiary structure prediction showed an alteration of the shape of the protein and crowding between domains. We also found a high incidence of polymorphisms (12.2%) in hypospadiac patients, (haplotype N589S/P286S in 4 cases). CONCLUSIONS CXorf6 mutations occur not only in 46 XY DSD but also in isolated hypospadias of varying severity. We also describe the first CAG repeat amplification of CXorf6. However, the specific events associated with these mutations and the precise function of CXorf6 remain to be investigated.