Functional study of distinct domains of Dux in improving mouse SCNT embryonic development†

Two-cell-like (2C-like) embryonic stem cells (ESCs) are a small group of ESCs that spontaneously express zygotic genome activation (ZGA) genes and repeats, such as Zscan4 and murine endogenous retrovirus with leucine (MERVL), and are specifically expressed in 2-cell-stage mouse embryos. Although numerous types of treatment and agents elevate the transition of ESCs to 2C-like ESCs, Dux serves as a critical factor in this transition by increasing the expression of Zscan4 and MERVL directly. However, the loss of Dux did not impair the birth of mice, suggesting that Dux may not be the primary transitioning factor in fertilized embryos. It has been reported that for 2-cell embryos derived from somatic cell nuclear transfer (SCNT) and whose expression of ZGA genes and repeats was aberrant, Dux improved the reprogramming efficiency by correcting aberrant H3K9ac modification via its C-terminal domain. We confirmed that the overexpression of full-length Dux mRNA in SCNT embryos improved the efficiency of preimplantation development (62.16% vs. 41.26% with respect to controls) and also increased the expression of Zscan4 and MERVL. Furthermore, we found that the N-terminal double homeodomains of Dux were indispensable for Dux localization and function. The intermediate region was essential for MERVL and Zscan4 activation, and the C-terminal domain was important for elevating level of H3K27ac. Mutant Dux mRNA containing N-terminal double homeodomains with the intermediate region or the C-terminal domain also improved the preimplantation development of SCNT embryos. This is the first report focusing on distinguishing functional domains of Dux in embryos derived from SCNT.