Differential expression of PPP1R12A transcripts, including those harbouring alternatively spliced micro-exons, in placentae from complicated pregnancies.

INTRODUCTION: Placenta-associated pregnancy complications, including pre-eclampsia (PE) and intrauterine growth restriction (IUGR) are conditions postulated to originate from initial failure of placentation, leading to clinical sequelae indicative of endothelial dysfunction. Vascular smooth muscle aberrations have also been implicated in the pathogenesis of both disorders via smooth muscle contractility and relaxation mediated by Myosin Light Chain Phosphatase (MLCP) and the oppositional contractile action of Myosin Light Chain Kinase. PPP1R12A is a constituent part of the MLCP complex responsible for dephosphorylation of myosin fibrils. We hypothesize that alternative splicing of micro-exons result in isoforms lacking the functional leucine zipper (LZ) domain which may give those cells expressing these alternative transcripts a tendency towards contraction and vasoconstriction. METHODS: Expression was determined by qRT-PCR. Epigenetic profiling consisted of bisulphite-based DNA methylation analysis and ChIP for underlying histone modifications. RESULTS: We identified several novel transcripts with alternative micro-exon inclusion that would produce LZ- PPP1R12A protein. qRT-PCR revealed some isoforms, including the PPP1R12A canonical transcript, are differentially expressed in placenta biopsies from PE and IUGR samples compared to uncomplicated pregnancies. DISCUSSION: We propose that upregulation of PPP1R12A expression in complicated pregnancies may be due to enhanced promoter activity leading to increased transcription as a response to physiological stress in the placenta, which we show is independent of promoter DNA methylation.

Single-cell multi-omic analysis profiles defective genome activation and epigenetic reprogramming associated with human pre-implantation embryo arrest.

During pre-implantation stages of mammalian development, maternally stored material promotes both the erasure of the sperm and oocyte epigenetic profiles and is responsible for concomitant genome activation. Here, we have utilized single-cell methylome and transcriptome sequencing (scM&T-seq) to quantify both mRNA expression and DNA methylation in oocytes and a developmental series of human embryos at single-cell resolution. We fully characterize embryonic genome activation and maternal transcript degradation and map key epigenetic reprogramming events in developmentally high-quality embryos. By comparing these signatures with early embryos that have undergone spontaneous cleavage-stage arrest, as determined by time-lapse imaging, we identify embryos that fail to appropriately activate their genomes or undergo epigenetic reprogramming. Our results indicate that a failure to successfully accomplish these essential milestones impedes the developmental potential of pre-implantation embryos and is likely to have important implications, similar to aneuploidy, for the success of assisted reproductive cycles.