In vitro capture and characterization of embryonic rosette-stage pluripotency between naive and primed states (I, bulk RNA-Seq data)

Naive pluripotent cells in the implanting mouse blastocyst generate a rosette structure before undergoing lumenogenesis to form the egg cylinder. Simultaneously, they acquire primed pluripotency, the ability to differentiate into the primary germ layers. The existence of discrete intermediate pluripotent states during this transition has not been demonstrated. We identify here a distinct rosette pluripotent state, defined by co-expression of naive factors with transcription factor OTX2. Downregulation of WNT signals in the blastocyst drives transition into rosette pluripotency by inducing OTX2. The rosette then activates MEK signals that induce lumenogenesis and drive progression to primed pluripotency. Consequently, combined WNT and MEK inhibition supports rosette-like stem cells (RSCs), a self-renewing naive-primed intermediate. RSCs gain a unique epigenome that includes erasure of constitutive heterochromatin and bivalent marking of primed pluripotency genes. Notwithstanding this primed chromatin landscape, WNT induces reversion to naive pluripotency. The rosette is therefore a reversible pluripotent intermediate where control over pluripotency progression and morphogenesis pivots from WNT to MEK signals.

着床期小鼠囊胚中的初始多能干细胞（naive pluripotent cells）在经历腔发生以形成卵柱前，会形成玫瑰花结结构。与此同时，这些细胞将获得始发多能性——即分化为初级胚层的能力。目前尚未有研究证实该多能性转变过程中存在独立的中间多能状态。本研究鉴定出一种独特的玫瑰花结多能状态，其核心特征为初始多能因子与转录因子OTX2的共表达。囊胚内WNT信号的下调可通过诱导OTX2的表达，推动细胞向玫瑰花结多能状态转变。随后，玫瑰花结结构会激活MEK信号，该信号可诱导腔发生并推动细胞进展至始发多能状态。因此，联合抑制WNT与MEK信号可维持玫瑰花结样干细胞（rosette-like stem cells, RSCs）的自我更新，这类细胞属于初始-始发中间态多能干细胞。RSCs具备独特的表观基因组，其特征包括组成型异染色质的清除以及始发多能性基因的二价标记。尽管拥有此类始发态染色质特征，WNT信号仍可诱导RSCs逆转为初始多能状态。综上，玫瑰花结结构是一种可逆的多能中间态，其多能性进展与形态发生的调控枢纽会从WNT信号切换至MEK信号。