Comprehensive DNA methylation profiling of sperm in male partners of couples with unexplained recurrent pregnancy loss

Background: Recurrent pregnancy loss (RPL) affects fertility problems in approximately 5% of couples, while the cause of RPL remains unknown in about half RPL cases, which is also called unexplained RPL. The male factors were associated with RPL in male partners, including chromosome abnormality and sperm DNA fragmentation. DNA methylation is one of the most extensively studied epigenetic factors that could help elucidate the mechanism underlying RPL in male partners. Results: We revealed DNA methylation alternations occurring in sperm of RPL patients compared with the controls by genome-wide DNA methylation beadchip, including a series of differentially methylated CpG positions and genes. Importantly, we validated that the CpG site cg17985533 and the region chr11:1997780-1997899 from the H19 imprinted maternally expressed transcript were significantly hypermethylated in sperm of RPL-related men with > 10% mean methylation difference by targeted bisulfite sequencing. Moreover, the receiver operating characteristic analysis showed that CpG site cg17985533 and region chr11:1997780-1997899 could distinguish RPL patients from controls, with an area under the curve of 0.7838 and 0.8125, sensitivity of 80% and 80%, and specificity of 80% and 75%, respectively. These results indicated that they could be potential biomarker for diagnosis of RPL in male partners. Conclusions: This study highlighted the importance of H19 gene methylation in differentiating RPL and control, and provided new insight for revealing potential epigenetic mechanisms for RPL in male partners.