Direct repression of Nanog and Oct4 by OTX2 modulates the contribution of epiblast-derived cells to germline and somatic lineage

Abstract

In mammals, the pre-gastrula proximal epiblast gives rise to primordial germ cells (PGCs) or somatic precursors in response to BMP4 and WNT signaling. Entry into the germline requires activation of a naïve-like pluripotency gene regulatory network (GRN). Recent work has shown that suppression of OTX2 expression in the epiblast by BMP4 allows cells to develop a PGC fate in a precise temporal window. However, the mechanisms by which OTX2 suppresses PGC fate are unknown. Here, we show that, in mice, OTX2 prevents epiblast cells from activating the pluripotency GRN by direct repression of Oct4 and Nanog. Loss of this control during PGC differentiation in vitro causes widespread activation of the pluripotency GRN and a deregulated response to LIF, BMP4 and WNT signaling. These abnormalities, in specific cell culture conditions, result in massive germline entry at the expense of somatic mesoderm differentiation. Increased generation of PGCs also occurs in mutant embryos. We propose that the OTX2-mediated repressive control of Oct4 and Nanog is the basis of the mechanism that determines epiblast contribution to germline and somatic lineage.

Differential repression of Otx2 underlies the capacity of NANOG and ESRRB to induce germline entry

“…In the absence of cytokines, OTX2 protein levels are sufficient to block activation of the PGCLC programme. Recent findings indicate that this repressive effect of OTX2 on the PCG programme results in large part from a direct repression of the Nanog and Oct4 genes (Figure 4A) (Di Giovannantonio et al, 2021). Induction of transgenic Nanog in EpiLCs shifts the balance between the mutual antagonists NANOG and OTX2 in favour of NANOG (Figure 4B).…”

“…In contrast, Otx2 deletion dramatically increases PGCLC numbers in vitro and raises PGC numbers in vivo (J. . Recently, OTX2 has been shown to act through cis-acting binding sites that repress transcription of Nanog and Oct4 (Di Giovannantonio et al, 2021). However, despite an increasing knowledge of the relationships between Esrrb, Nanog and Otx2, the interplay between these factors in PGC induction is not completely understood.…”

Differential repression of Otx2 underlies the capacity of NANOG and ESRRB to induce germline entry

“…In the absence of cytokines, OTX2 protein levels are sufficient to block activation of the PGCLC program. Recent findings indicate that this effect of OTX2 on the PCG program results largely from direct repression of Nanog and Oct4 ( Figure 4 A) ( Di Giovannantonio et al., 2021 ). Induction of transgenic Nanog in EpiLCs shifts the balance between the mutual antagonists NANOG and OTX2 in favor of NANOG ( Figure 4 B).…”

“…We have shown that entry to the germline is blocked when OTX2 expression is maintained during the first 2 days of EpiLC-PGCLC differentiation (Zhang et al, 2018a;Zhang and Chambers, 2019). In contrast, Otx2 deletion dramatically increases PGCLC numbers in vitro and raises PGC numbers in vivo (Zhang et al, 2018a) (legend continued on next page) Giovannantonio et al, 2021). However, despite increasing knowledge of the relationships among ESRRB, NANOG, and OTX2, the interplay among these factors in PGC induction is not fully understood.…”

“…In contrast, Otx2 deletion dramatically increases PGCLC numbers in vitro and raises PGC numbers in vivo ( Zhang et al., 2018a ). Recently, OTX2 has been shown to act through cis -acting binding sites that repress transcription of Nanog and Pou5f1 ( Oct4 ) ( Di Giovannantonio et al., 2021 ). However, despite increasing knowledge of the relationships among ESRRB, NANOG, and OTX2, the interplay among these factors in PGC induction is not fully understood.…”