Revealing the effects of lactate on bovine SCNT embryo development through transcriptome sequencing analyses

As a major energy source in the metabolism of early embryos, lactate also participates in regulating zygotic gene expression and subsequently contributes to preimplantation embryonic development. Nevertheless, the influence of lactate on embryonic development in bovine cloned embryos remains elusive. For this reason, this research explored the differences in metabolic pathways between in vitro fertilization (IVF) embryos and somatic cell nuclear transfer (SCNT) embryos during zygotic genome activation (ZGA) using Smart-seq and observed changes in SCNT embryo development in response to lactate supplementation. Weighted gene coexpression network analysis (WGCNA) revealed that LDHA functions as a hub gene that significantly influences the gene expression profile of 8-cell SCNT embryos. Compared with those of IVF embryos, SCNT embryos showed lower LDHA levels and lactate contents. Lactate supplementation was found to increase the developmental potential and blastocyst quality of SCNT embryos. Furthermore, the addition of lactate significantly increased the immunofluorescence intensity of both Pan Kla and H3K18la as well as the expression levels of the zygotic genes ZSCAN5B and SUPT4H1 in SCNT embryos. These results indicate that lactate deficiency leading to the downregulation of histone lactylation may be an important factor affecting the in vitro development of SCNT embryos.