Genome-Wide Mapping of 5-mC and 5-hmC in severely Preeclamptic Placentas.

Preeclampsia (PE) is a major contributor of maternal mortality with uncertain etiology. Recent studies suggested that epigenetic modifications, including DNA methylation, play a vital role in the development of PE. In this study, we have mapped genome-wide distribution of 5-methylcytosin (5-mC) and 5-hydroxymethylcytosine (5-hmC) using MeDIP and (h)MeDIP in the placentas from severely preeclamptic patients and normal controls. A total 194485 pooled 5-mC peaks and 138133 pooled 5-hmC peaks were identified, of which 714 5-mC peaks and 119 5-hmC peaks showed significant difference between patients and controls (>2-fold, p<0.05).To our knowledge, this is the first report of DHMRs (Differentially Hydroxy-Methylated Regions) in preeclamptic placenta. We not only confirmed the aberrant DNA methylated regions in the process of preeclampsia reported previously, but also identified unreported regions. A total of 4 selected DMRs (Differentially Methylated Regions) were also confirmed by MassARRAY EppiTYPER. Of these, PTPRN2, which had low level of 5-mC and high level of 5-hmC at gene body, was further verified to have lower methylation level at promoter regions in case group compared with controls. In conclusion, our study provided genome-wide distribution of 5-mC and 5-hmC in severe PE and normal controls, which have further clinical value for the identification of diagnostic and therapeutic markers for severe PE. Overall design: Examination of 5-mC and 5-hmC pattern in 4 control cases'' tissue and 4 severely Preeclamptic Placentas cases'' tissue.