Developmental peculiarities in placentae of ovine uniparental conceptuses

Abstract

Genomic imprinting is an epigenetic phenomenon regulating mono-allelic expression of genes depending on their parental origin. Defective genomic imprinting is involved in several placental disorders, such as intrauterine growth restriction and pre-eclampsia. Uniparental embryos, having maternal-only or paternal-only genomes (parthenogenotes [PAR] and androgenotes [AND], respectively), are useful models to study placentation. The aim of this work was to reveal the effect of parental genome (maternal and paternal) on placentation. To do this, uniparental (AND and PAR) and biparental (CTR) in vitro produced sheep embryos transferred to recipient females were collected at day 20 of pregnancy and their placentae were analyzed. qPCR analysis showed that imprinted genes (H19, IGF2R and DLK1) were expressed accordingly to their parental origin while the expression f DNA methyltransferases () was disregulated, especially in PAR (P < 0.05). AND placentae were significantly hypomethylated compared to both PAR and CTR (P = 0.023). Chorion-allantoid of AND showed impaired development of vessels and reduced mRNA expression of vasculogenetic factors (ANG2 P = 0.05; VEGFR2 P< 0.001; TIE2 P < 0.001). Morphologically, PAR placentae were characterized by abnormal structure of the trophoectodermal epithelium and reduced total number (P<0.03) of Trophoblastic Binucleate Cells. A reduced implantation rate of both classes of uniparental embryos (P<0.03) was also noted. Our results provide new insights into the characterization of uniparental embryos and demonstrate the complementary role of parental genomes for the correct establishment of pregnancy. Thus, our findings may suggest new targets to improve our understanding of the origin of imprinting-related placental dysfunction.

Identification of a Novel Imprinted Transcript in the Porcine GNAS Complex Locus Using Methylome and Transcriptome of Parthenogenetic Fetuses

“…Therefore, subsequent studies may employ this approach to reveal parental origin-specific imprinting landscape, through examining expression of particular imprinted transcripts by unique exons when multiple overlapping exonic regions are present. For imprinting research, uniparental embryos and placenta having solely maternal or paternal genome have been generated using reproductive technologies and are useful models to discover the roles of imprinted genes [21,22]. Our generation of parthenogenetic porcine fetuses, combining whole genome bisulfite sequencing and RNA sequencing of each individual in control and parthenote groups, further decreased genetic variations that could affect gene expression patterns independent from genomic imprinting status.…”