DNA methylation regulates RNA m⁶A modification through transcription factor SP1 during the development of porcine somatic cell nuclear transfer embryos

Epigenetic modifications play critical roles during somatic cell nuclear transfer (SCNT) embryo development. Whether RNA N6-methyladenosine (m(6) A) affects the developmental competency of SCNT embryos remains unclear. Here, we showed that porcine bone marrow mesenchymal stem cells (pBMSCs) presented higher RNA m(6) A levels than those of porcine embryonic fibroblasts (pEFs). SCNT embryos derived from pBMSCs had higher RNA m(6) A levels, cleavage, and blastocyst rates than those from pEFs. Compared with pEFs, the promoter region of METTL14 presented a hypomethylation status in pBMSCs. Mechanistically, DNA methylation regulated METTL14 expression by affecting the accessibility of transcription factor SP1 binding, highlighting the role of the DNA methylation/SP1/METTL14 pathway in donor cells. Inhibiting the DNA methylation level in donor cells increased the RNA m(6) A level and improved the development efficiency of SCNT embryos. Overexpression of METTL14 significantly increased the RNA m(6) A level in donor cells and the development efficiency of SCNT embryos, whereas knockdown of METTL14 suggested the opposite result. Moreover, we revealed that RNA m(6) A-regulated TOP2B mRNA stability, translation level, and DNA damage during SCNT embryo development. Collectively, our results highlight the crosstalk between RNA m(6) A and DNA methylation, and the crucial role of RNA m(6) A during nuclear reprogramming in SCNT embryo development.