BMP4 supports self-renewal of embryonic stem cells by inhibiting mitogen-activated protein kinase pathways

Abstract

The fate of pluripotent stem cells is tightly controlled during early embryonic development. Both the derivation and the maintenance of embryonic stem cells (ES cells) in vitro depend on feeder cell-derived growth factors that are largely unidentified. To dissect the mechanisms governing pluripotency, we conducted a screen to identify factors that are produced by mouse embryonic fibroblast STO cells and are required to maintain the pluripotency of ES cells. One of the factors is bone morphogenetic protein 4 (BMP4). Unexpectedly, the major effect of BMP4 on the self-renewal of ES cells is accomplished by means of the inhibition of both extracellular receptor kinase (ERK) and p38 mitogen-activated protein kinase (MAPK) pathways, and inhibitors of ERK and p38 MAPKs mimic the effect of BMP4 on ES cells. Importantly, inhibition of the p38 MAPK pathway by SB203580 overcomes the block in deriving ES cells from blastocysts lacking a functional Alk3, the BMP type IA receptor. These results uncover a paradigm for BMP signaling in the biology of pluripotent stem cells.E mbryonic stem cells (ES cells) are able to form all cell types of the body by following normal embryogenesis (1-3). The pluripotency of ES cells has attracted great attention for their potential use in tissue and cell therapy. However, the molecular and developmental mechanisms controlling pluripotency and differentiation of ES cells are largely unknown, and only a very limited number of genes has so far been shown to affect the fate decisions of inner cell mass (ICM) or ES cells. These genes include Oct4, Fgf4, H2az, Foxd3, Nanog,.Growth factors required for ES cell self-renewal are usually provided by feeder cells, or exogenously (13). Leukemiainhibiting factor (LIF) and its close relatives are the known propluripotency factors for mouse ES cells. It is unclear how many other growth factors or signaling pathways are required for the self-renewal of ES cells. To address these questions, we set out to identify such factors that affect the self-renewal of ES cells. To accomplish this, we isolated and screened sublines of the mouse embryonic fibroblast STO cells for their ability to support the self-renewal of ES cells by using Oct4-GFP as a convenient marker of pluripotency (14-16). By this approach in combination with gene expression profiling, we have identified bone morphogenetic protein 4 (BMP4) as part of the extracellular propluripotency cues. Also, our studies show that BMP4 and LIF have synergistic effect in teratoma formation. Moreover, a number of genes differentially expressed in ES cells cultured with or without exogenous BMP4 have been identified.One of these differentially expressed genes, X-linked inhibitor of apoptosis (Xiap), is expressed at higher levels in ES cells cultured in the presence of exogenous BMP4 than in its absence. XIAP has been implicated in connecting the type I receptors of BMPs and TGF-␤s with the mitogen-activated protein kinase (MAPK) p38 pathway (17)(18)(19)(20). Contrary to previous findings in which BMP signaling up-r...

The Drosophila ovary: an active stem cell community

“…In the Drosophila testis, the BMP signal produced by niche cells also functions as a short-range signal to control GSC self-renewal by repressing bam expression [44,45]. Intriguingly, BMP promotes self-renewal of mouse ES cells, but induces differentiation of skin and intestinal stem cells in mice [46][47][48][49][50]. Further studies on GSCs in the Drosophila may help provide insight into how BMP signaling has different functions in different stem cell systems.…”

Shh/BMP‐4 signaling pathway is essential for intestinal epithelial development during Xenopus larval‐to‐adult remodeling

“…The only result we obtained concerning epithelial proliferation is that excessive Chordin, that is, BMP-4 deficiency, results in the reduction of proliferation and the total number of adult progenitor cells. This finding suggests a possibility that a certain amount of BMP-4 may be essential for the maintenance and/or self-renewal of the intestinal stem cells, as proposed in other organs such as the ovary (Xie and Spradling, 1998;Fujiwara et al, 2001) and embryonic stem cells (Ying et al, 2003;Qi et al, 2004). To address its functions in the epithelial cell proliferation more precisely, further studies are necessary to distinguish effects of BMP-4 on stem cells from those on their descendant proliferating cells.…”

Roles of TGF-β family signaling in stem cell renewal and differentiation

“…Mouse embryos deficient in Smad4 display defective epiblast proliferation and delayed outgrowth of the inner cell mass [13], and mice lacking ALK-3 bone morphogenetic protein (BMP) type IA receptor) exhibit reduced cell proliferation in the epiblast [14], demonstrating that BMP signaling plays important roles in the maintenance of mouse ES cell identity. Qi et al [15] reported that BMP-4 provided by feeder cells is necessary for the maintenance of ES cell self-renewal, and that effect of BMP-4 is accomplished by means of inhibition of both extracellular receptor kinase (ERK) and p38 mitogen-activated protein kinase (MAPK) pathways. Inhibition of the p38 MAPK pathway by SB203580 was shown to overcome the block in deriving ES cells from blastocysts lacking ALK-3.…”