Abstract: The role of N6-Methyladenosine (m6A) abundances in formative pluripotency remains undefined. We examined mouse and human in vitro models enabling primordial germcell-like-cell (PGCLC) specification and somatic differentiation. Depletion of m6A by Mettl3 or Mettl14 knock-down or pharmacological METTL3 inhibition impairs germline entry. In mouse epiblast-like cells, m6A depletion increases embryonic Ras (Eras) dependent PI3K-AKT signaling. ERAS up-regulation lowers EZH2 coordinated H3K27me3 histone mark deposition, disrupting Oct4 distal enhancer silencing required for germline competence. In m6A depleted mouse formative stem cells, Eras facilitates the precocious up-regulation of somatic and germline transcription factors (TFs), including the germline repressor Otx2. Depletion of m6A in human formative cells elevates FGF dependent ERK activation. ERK up-regulates OTX2, repressing germline TFs upon PGCLC induction. Both mouse and human germline entry deficiency is accompanied by skewed somatic lineage differentiation. With the aid of genome-wide sequencing approaches, we identify how m6A orchestrates signaling dependent enhancer silencing and TF expression, critical for robust lineage competence.
Funding Source: Helse Sør-Øst Norwegian Research Fund (Project No. 39907) and the Norwegian Research Council 661 (Project No. 247656).
