Absence of SOCS3 reduces self-renewal and promotes differentiation in murine embryonic stem cells

¹ The Walter and Eliza Hall Institute of Medical Research, Parkville, Victoria, Australia
² AMRAD Corporation Ltd., Richmond, Victoria, Australia

^* To whom correspondence should be addressed. E-mail: robb{at}wehi.edu.au.

	Abstract

Leukaemia inhibitory factor (LIF) is required to maintain pluripotency and permit self-renewal of murine embryonic stem (ES) cells. LIF binds to a receptor complex of LIFR and gp130 and signals via the JAK/STAT pathway, with signalling attenuated by SOCS proteins. Recent in vivo studies have highlighted the role of SOCS3 in negative regulation of signalling via gp130. To determine the role of SOCS3 in ES cell biology, SOCS3 null ES cell lines were generated. When cultured in LIF levels that sustain self-renewal of wild type cells, SOCS3 null ES cell lines exhibited reduced self-renewal and increased differentiation into primitive endoderm. Absence of SOCS3 enhanced JAK/STAT and ERK1/2 MAPK signal transduction via gp130, with levels of phosphorylated STAT1, STAT3 SHP2 and ERK1/2 being increased in the steady state and in response to LIF stimulation. Attenuation of ERK signalling by addition of MEK inhibitors to SOCS3 null ES cell cultures rescued the differentiation phenotype, but did not restore proliferation to wild type levels. In summary, SOCS3 plays a crucial role in regulation of the LIF signalling pathway in murine ES cells. Its absence perturbs the balance between activation of the JAK/STAT and SHP2-ERK1/2 MAPK pathways resulting in diminished self-renewal and increased potential for differentiation into the primitive endoderm lineage.