Abstract
ABSTRACTThe cytokine leukaemia inhibitory factor (LIF) promotes self-renewal of mouse embryonic stem cells (ESCs) through activation of the transcription factor Stat3. However, the contribution of other ancillary pathways stimulated by LIF in ESCs, such as the MAPK and PI3K pathways, is less well understood. We show here that naive-type mouse ESCs express high levels of a novel effector of the MAPK and PI3K pathways. This effector is an isoform of the Gab1 (Grb2-associated binder protein 1) adaptor protein that lacks the N-terminal pleckstrin homology (PH) membrane-binding domain. Although not essential for rapid unrestricted growth of ESCs under optimal conditions, the novel Gab1 variant (Gab1β) is required for LIF-mediated cell survival under conditions of limited nutrient availability. This enhanced survival is absolutely dependent upon a latent palmitoylation site that targets Gab1β directly to ESC membranes. These results show that constitutive association of Gab1 with membranes through a novel mechanism promotes LIF-dependent survival of murine ESCs in nutrient-poor conditions.
Highlights
Embryonic stem cell (ESCs) are pluripotent cell lines derived from the inner cell mass of the blastocyst
LIF receptor (LIFR)-gp130 signalling has essential roles during early embryonic development that provide the physiological rationale for the contribution of this signalling pathway to the growth and selfrenewal of embryonic stem cells (ESCs) in culture (Do et al, 2013; Nichols et al, 2001)
We report the identification of a novel variant form of the adaptor protein Gab1 (Gab1β) that contributes to leukaemia inhibitory factor (LIF)-dependent survival of ESCs under conditions of limited nutrient availability
Summary
Embryonic stem cell (ESCs) are pluripotent cell lines derived from the inner cell mass of the blastocyst They are immortal, differentiate into all foetal cell types in vitro, and most remarkably, when reintroduced into an appropriately staged embryo, reinitiate normal development to form all foetal tissues, including the germ line (Martello and Smith, 2014). The biological capacity and value of ESCs relies upon the fidelity with which their developmental potential can be maintained in culture and as a consequence, considerable efforts have been made to understand the role of self-renewal signals and the transcriptional factors that maintain ESC pluripotency (Ying and Smith, 2017). The requirement for this cytokine in ESCs of other species is unclear, LIF is included as a supplement in culture media that support human stem cell lines thought to be equivalent to mouse ESCs, and non-rodent pluripotent stem cells can respond to LIF, suggesting that this cytokine signalling pathway may have a general role in supporting pluripotent stem cells of mammals (Guo et al, 2016; Takashima et al, 2014; Theunissen et al, 2014; Thomson et al, 2012)
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