Dynamic changes of 3'UTR length during oocyte-to-zygote transition of in vitro pig embryos.

Alternative polyadenylation (APA) generates different 3'-untranslated regions (3'UTRs) to regulate gene expression and localization, and affects a variety of biological processes. Here, we characterized the 3'UTR dynamics during the oocyte-to-zygote transition by analyzing our previously reported porcine single cell RNA-seq (scRNA-seq) datasets (in vitro matured metaphase II (MII) oocytes, in vitro fertilized zygotes (IVF1) and parthenogenetically activated 1-cell embryos (PA1)). After IVF1 vs. MII comparison, Dynamic analyses of APA from RNA-seq (DaPars) method identified 139 mRNAs with significantly different 3'UTRs (Padj.≤0.05), mainly enriched in cell cycle, regulation of cyclin-dependent protein kinase activity, histone modification, mRNA surveillance, and regulation of actin cytoskeleton. For PA1 vs. MII comparison, 105 mRNAs with significantly different 3'UTRs (Padj.≤0.05) were identified to be mainly enriched in intracellular transport, mitotic spindle organization, cell cycle, pyruvate metabolism, and glycolysis/gluconeogenesis. Moreover, there were 7 mRNAs with more significant 3'UTR differences (|△PDUI|≥0.45 and |log 2 (PDUI ratio)|≥0.59) respectively in IVF1 vs. MII (Lrp2bp, Mtfr2, Nhlrc2, Psip1, Smu1, Ssr1 and Wtap) and PA1 vs. MII (Asf1b, Dimt1, Nap1l1, Ncoa4, Nudt21, Pnn and Rpl15) comparisons. Integrative genomics viewer (IGV) analysis further identified that 3'UTRs of Psip1, Smu1, Ssr1 and Wtap had more than 140nt average length changes, whereas those of Dimt1, Nap1l1 and Rpl15 were shortened with more than 460nt. Regulatory elements (PAS, CPE, microRNA binding sites and m 6 A sites) in 3'UTRs of different lengths were predicted. Our findings provide useful information to further investigate the molecular mechanism of 3'UTR in regulating the oocyte-to-zygote transition of pig embryos.