Genomic variants of ATF3 in patients with hypospadias

Abstract

Purpose: ATF3, an estrogen responsive gene expressed during genital development, could be implicated in the etiology of hypospadias. ATF3 is up-regulated in the foreskin of patients with hypospadias and is implicated in suppression of the cell cycle, which may interfere with urethral cell growth. We sought to investigate the sequence of ATF3 in patients with hypospadias.

Material and methods: Direct sequencing of coding exons and splice sites of ATF3 was performed in 41 boys with hypospadias and 30 controls. In addition, ATF3 expression in 1 human fetal penis with and 1 without hypospadias was studied by immunohistochemical analysis.

Results: A missense variant (L23M) was identified in a boy with anterior hypospadias. This amino acid is highly conserved. Three genomic variants (C53070T, C53632A, Ins53943A) were found in or close to exon 6 in patients with perineal, penoscrotal and anterior hypospadias. This important exon includes splice sites for an alternative transcript (ATF3DeltaZip) that have been implicated in regulation of the function of ATF3. None of these genomic variants was present in controls. Immunochemical analysis revealed that in normal fetuses ATF3 is not expressed in and around the urethra, while in patients with hypospadias ATF3 is over expressed in the urethral plate and subcutaneous tissue, especially around the ectopic orifice of the urethra.

Conclusions: Genomic variants of ATF3 are present in 10% of our patients with hypospadias. We also report an abnormal expression pattern of ATF3 in a hypospadiac fetus. The direct implication of ATF3 in the occurrence of hypospadias remains to be confirmed by functional studies of the genomic variants we describe.