DUX: One Transcription Factor Controls 2-Cell-like Fate

Abstract

The double homeobox (Dux) gene, encoding a double homeobox transcription factor, is one of the key drivers of totipotency in mice. Recent studies showed Dux was temporally expressed at the 2-cell stage and acted as a transcriptional activator during zygotic genome activation (ZGA) in embryos. A similar activation occurs in mouse embryonic stem cells, giving rise to 2-cell-like cells (2CLCs). Though the molecular mechanism underlying this expanded 2CLC potency caused by Dux activation has been partially revealed, the regulation mechanisms controlling Dux expression remain elusive. Here, we discuss the latest advancements in the multiple levels of regulation of Dux expression, as well as Dux function in 2CLCs transition, aiming to provide a theoretical framework for understanding the mechanisms that regulate totipotency.

Keywords: 2-cell-like cells; Dux; gene regulation; totipotency.

Figure 1

Transcriptional regulation of Dux expression by transcription factors. DPPA2/4 and NELFA transcriptionally activate Dux. Meanwhile, DUX can activate Zscan4 which will upregulate DPPA2/4. PIAS4 will repress DPPA2/4 expression through the SUMOylating of DPPA2. DPPA2/4, developmental pluripotency associated 2/4; PIAS4, protein inhibitor of activated STAT 4; NELFA, negative elongation factor complex member A; ZSCAN4, SCAN domain containing 4; TOP2A, DNA topoisomerase 2a; DUX, double homeobox.

Figure 2

Regulation of Dux expression by epigenetic modifications. (A): Dux expression regulated by histone modifications transcription. The activation of H3K9me3 regulators caused by YTHDC1 and LIN28 will enhance the H3K9me3 levels and silence Dux expression finally. (B): Dux expression regulated by DNA modifications. DNA methylations caused by DNMT1/UHRF1 and TET repress Dux expression. LINE1, long interspersed nuclear element-1; SETDB1, SET domain bifurcated histone lysine methyltransferase 1; KAP1, KRAP-associated transcriptional repressor; TRIM28, tripartite motif-containing protein 28; PRC1.6, polycomb-repressive complexes 1.6; NCL, nucleolin; ZSCAN4C, SCAN domain containing 4C; DNMT1, DNA methyltransferase 1; UHRF1, ubiquitin like with PHD and ring finger domains 1; GADD45, growth arrest and DNA damage 45; TET, ten-eleven translocation; SMCHD1, structural maintenance of chromosomes flexible hinge domain containing 1.

Figure 3

Signaling pathways involved in the regulation of Dux expression. DNA damage lead to P53 activation and then upregulates Dux expression. CX-5461 can decrease rRNA biogenesis and activate Dux expression. Retinoic acid participates in the NELFA-mediated Dux activation, and 2-DG inhibited glycolytic flux and activated Dux expression. DPPA2/4, developmental pluripotency associated 2/4; NELFA, negative elongation factor complex member a; TOP2A, DNA topoisomerase 2a; P53, tumor protein 53.

Figure 4

The 3D genome conformation determines the expression of Dux. The disruption of chromatin organization by the depletion of CTCF or addition with CX-5461 will lead to the lower TAD strength and TAD insulation and, finally, upregulate Dux expression. ESCs, embryonic stem cells; 2CLCs, 2-cell-like cells; CTCF, CCCTC-binding factor; TAD, topologically associating domains.