Distinct functions of BMP4 during different stages of mouse ES cell neural commitment

Abstract

SUMMARYBone morphogenetic protein (BMP) signaling plays a crucial role in maintaining the pluripotency of mouse embryonic stem cells (ESCs) and has negative effects on ESC neural differentiation. However, it remains unclear when and how BMP signaling executes those different functions during neural commitment. Here, we show that a BMP4-sensitive window exists during ESC neural differentiation. Cells at this specific period correspond to the egg cylinder stage epiblast and can be maintained as ESC-derived epiblast stem cells (ESD-EpiSCs), which have the same characteristics as EpiSCs derived from mouse embryos. We propose that ESC neural differentiation occurs in two stages: first from ESCs to ESD-EpiSCs and then from ESD-EpiSCs to neural precursor cells (NPCs). We further show that BMP4 inhibits the conversion of ESCs into ESD-EpiSCs during the first stage, and suppresses ESDEpiSC neural commitment and promotes non-neural lineage differentiation during the second stage. Mechanistic studies show that BMP4 inhibits FGF/ERK activity at the first stage but not at the second stage; and IDs, as important downstream genes of BMP signaling, partially substitute for BMP4 functions at both stages. We conclude that BMP signaling has distinct functions during different stages of ESC neural commitment.

miR-23a, miR-24 and miR-27a protect differentiating ESCs from BMP4-induced apoptosis

“…In particular, BMP4 represents an insurmountable barrier to the transition of ESCs into EpiSCs and then to the differentiation of EpiSCs into neuroectodermal precursors, thus favoring the choice of the mesendodermal fate. 2 Therefore, it is quite expected that, in vivo, a fine tuning of the intracellular signaling downstream of BMP4 and of its crosstalk with other signaling pathways should exist to allow cells of the embryo to proceed through the various developmental stages. The results shown in this article uncover a new regulatory mechanism of the signaling downstream of BMP4 based on a small group of miRNAs encoded by two very similar miR-cluster genes.…”

“…ESC differentiation into neuroectoderm was induced though SFEB formation. 2,20 SFEBs were induced by placing 1x10 6 ESCs in 100-mm Petri dishes in the following differentiation medium: GMEM supplemented with 2 mM glutamine, 1 mM sodium pyruvate, 1 × nonessential amino acids, 0.1 mM β-mercaptoethanol and 10% KSR.…”

“…They can be grown indefinitely in vitro and induced to differentiate, thus mimicking two events taking place in the blastocyst: (i) the differentiation of the cells of the inner cell mass into epiblast cells and (ii) the commitment of epiblast cells to neuroectodermal or mesendodermal precursors. 1,2 These differentiation events are regulated by extrinsic signals. BMP4, a member of the TGF-β superfamily of cytokines, has a crucial role in ESCs.…”

“…First, BMP4 acts by regulating ESC-epiblast transition and then by suppressing neural differentiation and promoting non-neural lineage formation. 2 Moreover, BMP4 promotes the differentiation towards mesendodermal lineages and also regulates, either positively or negatively, the further commitment of mesendodermal precursors into their different fates. [5][6][7][8] Gene expression in ESCs is regulated by a complex network of transcription factors.…”

“…It has been demonstrated that treatment of differentiating ESCs into SFEBs with high doses of BMP4 (10 ng/ml) blocks differentiation thus maintaining pluripotency. 2 In contrast, it was also observed that low doses of BMP4 induce apoptosis during epidermal differentiation of ESCs. 29 We reasoned that suppression of miR-clusters can result in an enhancement of the endogenous signaling that mimics the exposure of the cells to low doses of BMP4.…”