Transient Dux expression facilitates nuclear transfer and induced pluripotent stem cell reprogramming

Abstract

Cloned animals generated by somatic cell nuclear transfer (SCNT) have been reported for many years; however, SCNT is extremely inefficient, and zygotic genome activation (ZGA) is required for SCNT‐mediated somatic cell reprogramming. To identify candidate factors that facilitate ZGA in SCNT‐mediated reprogramming, we performed siRNA‐repressor and mRNA‐inducer screenings, which reveal Dux, Dppa2, and Dppa4 as key factors enhancing ZGA in SCNT. We show that direct injection of ZGA inducers has no significant effect on SCNT blastocyst formation; however, following the establishment of an inducible Dux transgenic mouse model, we demonstrate that transient overexpression of Dux not only improves SCNT efficiency but also increases that of chemically induced pluripotent stem cell reprogramming. Moreover, transcriptome profiling reveals that Dux‐treated SCNT embryos are similar to fertilized embryos. Furthermore, transient overexpression of Dux combined with inactivation of DNA methyltransferases (Dnmts) further promotes the full embryonic development of SCNT‐derived animals. These findings enhance our understanding of ZGA‐regulator function in somatic reprogramming.

Functions and Regulation of Endogenous Retrovirus Elements during Zygotic Genome Activation: Implications for Improving Somatic Cell Nuclear Transfer Efficiency

“…Resent research has also demonstrated that the ectopic expression of DUX alone in mouse embryonic stem cells can activate MERVL, accompanied by a "two-cell-like" transcriptional program, which often corresponds with ZGA [27,29]. Indeed, transient overexpression of DUX can significantly increase the expression of MERVL, indicating that DUX acts as a core factor for ZGA by enhancing the expression of ZGA-specific genes such as Zscan4, Zfp352, and MERVL [72,73]. Given the versatility of ERVs, it seems likely that ancestral DUX proteins strengthened their control over the ZGA process by regulating ERVs [28].…”

“…Because the timely expression of ZGA is indispensable for the development of cloned embryos, and DUX, acting as a pioneer transcription factor, can trigger the activation of ERVs and ZGA-specific genes [27][28][29], it is reasonable to suspect that exogenous DUXtreated cloned embryos will acquire higher developmental competence. Yang et al demonstrated that a direct injection of DUX has no significant effect on SCNT blastocyst formation, whereas the transient expression of DUX indeed improves SCNT efficiency, producing a transcriptome profile similar to that of fertilized embryos [73]. The ZGA process is under the control of a "zygotic clock", and the improvement to the efficiency of cloned embryo development induced by DUX is time-dependent.…”

“…Conversely, the transient expression of DUX via dox-inducible system during the 11-25 h post-activation period did increase the blastocyst formation rate. Moreover, the transient expression of DUX significantly increased the expression of ZGA-related genes, such as ZSCAN4 and MERVL [73]. The dox-inducible system is a powerful tool for initiating the transient expression of exogenous genes.…”

“…This elevated SCNT efficiency benefits from the advantages of the dox-inducible system, which allows the regulation of DUX expression in a spatiotemporal-specific manner via switching between dox-containing and dox-free culture medium, therefore ensuring a timely entry into the ZGA state along with a timely exit from it (Figure 1). cantly increased the expression of ZGA-related genes, such as ZSCAN4 and MERVL [73]. The dox-inducible system is a powerful tool for initiating the transient expression of exogenous genes.…”

Manipulating the Epigenome in Nuclear Transfer Cloning: Where, When and How

“…Moreover, transcriptome profiling revealed that DUX expressing cloned embryos are similar to fertilized embryos. Furthermore, overexpression of DUX combined with knockdown of DNMTs promoted the full-term of cloned embryos [ 118 ].…”