Methylation aberrations in partner spermatozoa and impaired expression of imprinted genes in the placentae of early-onset preeclampsia.

Introduction: Disturbed paternal epigenetic status of imprinted genes has been observed in infertility and recurrent spontaneous abortions. Shallow placentation has been associated with early-onset preeclampsia. Hence, the present study aimed to investigate the methylation patterns of imprinted genes involved in placental development, in the spermatozoa of partners of women experiencing preeclampsia.

Methods: The study involved recruitment of couples into preeclampsia (n = 14) and control (n = 25) groups. Methylation analysis of imprinted gene differentially methylated regions (DMRs) and LINE1 repetitive element was carried out by pyrosequencing in the spermatozoa and placental villi. Global 5 mC levels in the spermatozoa were measured through ELISA. Expression of imprinted genes was quantified in the placental villi by real time qPCR. Association of birth weight with DNA methylation and gene expression was assessed.

Results: KvDMR, PEG3 DMR, PEG10 DMR and DLK1-GTL2 IG-DMR were differentially methylated in the spermatozoa and placental villi of preeclampsia group. Global 5 mC content and LINE1 methylation levels did not differ between the spermatozoa of the two groups. Increased transcript levels of PEG3, IGF2, DLK1, PHLDA2 and CDKN1C were observed in the preeclamptic placental villi. Birth weight showed significant association with KvDMR, PEG10 DMR, DLK1-GTL2 IG-DMR and LINE1 methylation levels in the spermatozoa. DLK1 expression levels showed a negative association with birth weight.

Discussion: The study highlighted the paternal contribution to early-onset preeclampsia, in the form of disrupted sperm DNA methylation patterns at imprinted gene loci. These loci, after further evaluation in future studies, could serve as sperm-based preeclampsia predictive markers, for couples planning pregnancy.