Expression of miRNAs Associated With Embryo Development and DNA Damage Response in Porcine Embryos

Embryo genome activation (EGA) is a crucial event implicated in proper embryonic development. Similarly, the DNA Damage Response (DDR) is essential for correcting or preventing occasional errors during embryonic cell division that could result in embryo development arrest or the propagation of genetic abnormalities. Although both EGA and DDR are regulated by epigenetic mechanisms, the role of microRNAs (miRNAs) in these processes has not been explored in pig embryos. Herein, we assessed the abundance of miRNAs linked to embryo development and DDR across four developmental stages: Day 2 (D2), Day 3 (D3), and Day 4 (D4), and at the blastocyst stage, as well as after DNA damage induction. mRNA levels of EGA-related genes confirmed our timepoints as representing EGA timeframe, while immunofluorescence for γH2AX validated DNA damage induction. Significant decrease in blastocyst rate and total cell number per blastocyst was detected in UV-exposed embryos. Analysis of miRNA abundance revealed increased levels of miR-200a-5p on D3, which were partially maintained on D4. Both miR-15a and miR-24-3p increased on D4, but their levels were downregulated in UV-exposed embryos at the same stage of development. In blastocysts, UV exposure upregulated miR-29a-3p and miR-344b-3p. Together, these findings provide the first characterization of miRNAs expression in porcine embryos during EGA and following DNA damage induction.