27 Transcriptome Comparison of Parthenogenetic vs. Biparental Embryos in Beef Cattle

This experiment aimed to determine differences in circulating pregnancy-associated glycoprotein (PAG) concentrations, differentially expressed genes (DEGs), and comparative gene ontology profiles between parthenogenetic embryos (PA; absence of paternal genetics) and biparental control embryos (CON). PA embryos were produced in vitro using a validated chemical activation method, and CON embryos were produced in vitro using industry standard techniques. A blood sample was collected on day 31, and PAG concentrations were determined by an in-house ELISA. Transrectal ultrasonography was performed daily to monitor conceptus development. Cows (n = 30) were synchronized, underwent embryo transfer [ET; 7 days after onset of estrus (day 0)] and were euthanized at approximately day 31 of gestation. Tissues from endometrium (EM), trophectoderm (TE), and corpus luteum (CL) were collected and sequenced from both groups (3 PA; 3 CON). Average PAG concentrations between PA and CON on day 31 were 0.81±0.44 ng/mL and 5.23±0.44 ng/mL (P = 0.01), respectively. When comparing PA to CON, there were 969 DEG in the EM (599 genes upregulated; 269 genes downregulated; 101 nonannotated genes) and 250 DEG in the TE (163 genes upregulated; 47 downregulated; 40 nonannotated genes). Comparative gene ontology profiles between DEGs showed an upregulation in immune system-associated activities and extracellular matrix interactions and a downregulation in redox reactions and proteolytic activities involving PAGs for PA as compared to CON. Similarly, the TE comparisons showed an upregulation in prolactin (PRL) inhibiting pathways and a downregulation in structural molecule activity and signaling for PA as compared to CON. The DEGs observed in PAs show significant decreases in conceptus-derived products and gene ontology profiles associated with pregnancy. Overall, these findings demonstrate that uniparental embryos can be a useful model to better understand pregnancy development and loss in cattle.