title: Distinct Wnt-driven primitive streak-like populations reflect in vivo lineage precursors.
abstract: During gastrulation, epiblast cells are pluripotent and their fate is thought to be constrained principally by their position. Cell fate is progressively restricted by localised signalling cues from areas including the primitive streak. However, it is unknown whether this restriction accompanies, at the individual cell level, a reduction in potency. Investigation of these early transition events in vitro is possible via the use of epiblast stem cells (EpiSCs), self-renewing pluripotent cell lines equivalent to the postimplantation epiblast. Strikingly, mouse EpiSCs express gastrulation stage regional markers in self-renewing conditions. Here, we examined the differentiation potential of cells expressing such lineage markers. We show that undifferentiated EpiSC cultures contain a major subfraction of cells with reversible early primitive streak characteristics, which is mutually exclusive to a neural-like fraction. Using in vitro differentiation assays and embryo grafting we demonstrate that primitive streak-like EpiSCs are biased towards mesoderm and endoderm fates while retaining pluripotency. The acquisition of primitive streak characteristics by self-renewing EpiSCs is mediated by endogenous Wnt signalling. Elevation of Wnt activity promotes restriction towards primitive streak-associated lineages with mesendodermal and neuromesodermal characteristics. Collectively, our data suggest that EpiSC pluripotency encompasses a range of reversible lineage-biased states reflecting the birth of pioneer lineage precursors from a pool of uncommitted EpiSCs similar to the earliest cell fate restriction events taking place in the gastrula stage epiblast.
authors.affiliation: MRC Centre for Regenerative Medicine, Institute for Stem Cell Research, School of Biological Sciences, University of Edinburgh, 5 Little France Drive, Edinburgh EH16 4UU, UK.
authors.forename: Anestis
authors.initials: A
authors.lastname: Tsakiridis
authors.forename: Yali
authors.initials: Y
authors.lastname: Huang
authors.forename: Guillaume
authors.initials: G
authors.lastname: Blin
authors.forename: Stavroula
authors.initials: S
authors.lastname: Skylaki
authors.forename: Filip
authors.initials: F
authors.lastname: Wymeersch
authors.forename: Rodrigo
authors.initials: R
authors.lastname: Osorno
authors.forename: Costas
authors.initials: C
authors.lastname: Economou
authors.forename: Eleni
authors.initials: E
authors.lastname: Karagianni
authors.forename: Suling
authors.initials: S
authors.lastname: Zhao
authors.forename: Sally
authors.initials: S
authors.lastname: Lowell
authors.forename: Valerie
authors.initials: V
authors.lastname: Wilson
mesh_terms: D000818:Animals; D002454:Cell Differentiation; D019070:Cell Lineage; D002478:Cells, Cultured; D005775:Gastrula / Q000166:cytology / Q000196:embryology / Q000378:metabolism; D054262:Gastrulation / Q000502:physiology; D005855:Germ Layers / Q000166:cytology* / Q000196:embryology / Q000378:metabolism; D051379:Mice; D008822:Mice, Transgenic; D054258:Neural Plate / Q000166:cytology / Q000196:embryology / Q000378:metabolism; D039904:Pluripotent Stem Cells / Q000145:classification / Q000166:cytology / Q000378:metabolism; D054240:Primitive Streak / Q000166:cytology* / Q000196:embryology; D060449:Wnt Signaling Pathway
keywords: Epiblast stem cells; Gastrulation; Heterogeneity; Mouse; Neuromesodermal progenitors; Primitive Streak; Wnt signalling