Genome-wide methylation analysis in patients with proximal hypospadias - a pilot study and review of the literature

In patients with proximal hypospadias, often no genetic cause is identified despite extensive genetic testing. Many genes involved in sex development encode transcription factors with strict timing and dosing of the gene products. We hypothesised that there might be recurrent differences in DNA methylation in boys with hypospadias and that these might differ between patients born small versus appropriate for gestational age. Genome-wide Methylated DNA sequencing (MeD-seq) was performed on 32bp LpnPI restriction enzyme fragments after RE-digestion in leucocytes from 16 XY boys with unexplained proximal hypospadias, one with an unexplained XX testicular disorder/difference of sex development (DSD) and twelve, healthy, sex- and age-matched controls. Five of seven differentially methylated regions (DMRs) between patients and XY controls were in the Long Intergenic Non-Protein Coding RNA 665 (LINC00665; CpG24525). Three patients showed hypermethylation of MAP3K1. Finally, no DMRs in XX testicular DSD associated genes were identified in the XX boy versus XX controls. In conclusion, we observed no recognizable epigenetic signature in 16 boys with XY proximal hypospadias and no difference between children born small versus appropriate for gestational age. Comparison to previous methylation studies in individuals with hypospadias did not show consistent findings, possibly due to the use of different inclusion criteria, tissues and methods.