p53 convergently activates Dux/DUX4 in embryonic stem cells and in facioscapulohumeral muscular dystrophy cell models

Abstract

ertilization and early embryogenesis involve the transition from specialized unipotent gametes to totipotent embryos. After fertilization, mammalian embryos rely on maternally deposited RNA but subsequently initiate ZGA during which embryonic transcription begins 1 . Diverse mechanisms control the timing of ZGA, such as controlling RNA polymerase activity, the nuclear/ cytoplasmic ratio, or translation of critical ZGA transcription factors (TFs) in Caenorhabditis elegans, Drosophila melanogaster or Danio rerio, respectively 1 . Currently, we have an incomplete understanding of how the transcriptional machinery (RNA polymerases) and/or sequence-specific TFs dictate the timing of ZGA in mammals and contribute to developmental potential.Recent work identified the TF DUX (DUX4 in humans) as a key regulator of ZGA gene expression 2-5 . When ectopically expressed in cells, DUX and DUX4 activate many ZGA genes, including the earliest wave of ZGA genes in humans and mice 2,3 . However, the extent to which DUX is required for appropriate ZGA is unclear, as the reported effect of genetic loss of Dux ranges from minor molecular to major transcriptional defects and decreased development in mouse or human embryos 4-6 .To study ZGA using a cellular model, we and others have used 2C-embryo-like cells (2CLCs), which are an endogenously fluctuating subpopulation of mouse embryonic stem cells (mESCs) that recapitulate several key features of ZGA 7 . The 2CLCs activate transcripts characteristic of the 2C mouse embryo (including Dux,

Developmental Acquisition of p53 Functions

“…Studies on the role of p53 in ground-state 2iESCs produced contradictory results that mirror those reported for naïve ESCs. Two studies in mouse 2iESCs revealed that DNA damage induced either by aphidicolin inhibition of DNA polymerase-alpha or doxorubicin inhibition of topoisomerase II activates genes characteristic of zygotic gene expression in mouse 2-cell to 4-cell embryos [161,162]. Both studies concluded that the mechanism driving this expression is mediated by an ATR and CHK1 response to double-strand DNA breaks.…”

“…Both studies concluded that the mechanism driving this expression is mediated by an ATR and CHK1 response to double-strand DNA breaks. However, one study concluded that activation required p53 expression [162], whereas the other study concluded that it did not [161]. Critical experiments in which p53+/+ and p53-/-2iESCs were compared were carried in both studies, but with opposite results.…”

“…Three studies have reported the effects of doxorubicin on mouse p53+/+ and p53-/-2iESCs. One study cultured 2iESCs with 1µM doxorubicin for 6 hours and concluded that the DNA damage response was p53-dependent [162]. Another study carried out the same experiment using 1µg/mL (1.84µM) doxorubicin for 48 hours and concluded that the DNA damage response was p53-independent [161].…”

Developmental Acquisition of p53 Functions

“…Studies on the role of p53 in ground-state 2iESCs produced contradictory results that mirror those reported for naïve ESCs. Two studies in mouse 2iESCs revealed that DNA damage induced either by aphidicolin inhibition of DNA polymerase-α or doxorubicin inhibition of topoisomerase II activates genes characteristic of zygotic gene expression in mouse 2-cell to 4-cell embryos [161,162]. Both studies concluded that the mechanism driving this expression is mediated by an ATR and CHK1 response to double-strand DNA breaks.…”

“…Both studies concluded that the mechanism driving this expression is mediated by an ATR and CHK1 response to double-strand DNA breaks. However, one study concluded that activation required p53 expression [162],…”