FGF dependent regulation of Zfhx1b gene expression promotes the formation of definitive neural stem cells in the mouse anterior neurectoderm.
BACKGROUND
Mouse definitive neural stem cells (NSCs) are derived from a population of LIF-responsive primitive neural stem cells (pNSCs) within the neurectoderm, yet details on the early signaling and transcriptional mechanisms that control this lineage transition are lacking. Here we tested whether FGF and Wnt signaling pathways can regulate Zfhx1b expression to control early neural stem cell development.


RESULTS
By microinjecting FGF8b into the pro-amniotic cavity ex vivo at 7.0 days post-coitum (dpc) and culturing whole embryos, we demonstrate that neurectoderm-specific gene expression (for example, Sox2, Nestin, Zfhx1b) is increased, whereas Wnt3a represses neurectoderm gene expression. To determine whether FGF signaling also mediates the lineage transition from a pNSC to a NSC, 7.0-dpc embryos were microinjected with either FGF8b or inhibitors of the FGF receptor-MAP kinase signaling pathway ex vivo, cultured as whole embryos to approximately 8.5 dpc and assayed for clonal NSC colony formation. We show that pre-activation of FGF signaling in the anterior neurectoderm causes an increase in the number of colony forming NSCs derived later from the anterior neural plate, whereas inhibition of FGF signaling significantly reduces the number of NSC colonies. Interestingly, inhibition of FGF signaling causes the persistence of LIF-responsive pNSCs within the anterior neural plate and over-expression of Zfhx1b in these cells is sufficient to rescue the transition from a LIF-responsive pNSC to an FGF-responsive NSC.


CONCLUSIONS
Our data suggest that definitive NSC fate specification in the mouse neurectoderm is facilitated by FGF activation of Zfhx1b.
Dang
Lan T H
LT
Department of Cell and Systems Biology, University of Toronto, Toronto, ON, Canada.
Tropepe
Vincent
V
D000818:Animals; D002454:Cell Differentiation / Q000235:genetics; D019070:Cell Lineage / Q000187:drug effects / Q000235:genetics; D049109:Cell Proliferation / Q000187:drug effects; D002478:Cells, Cultured; D003114:Colony-Forming Units Assay; D004475:Ectoderm / Q000196:embryology*; D051524:Fibroblast Growth Factor 8 / Q000235:genetics / Q000494:pharmacology; D005346:Fibroblast Growth Factors / Q000235:genetics* / Q000494:pharmacology; D018507:Gene Expression Regulation, Developmental / Q000187:drug effects / Q000235:genetics; D018398:Homeodomain Proteins / Q000235:genetics*; D020935:MAP Kinase Signaling System / Q000187:drug effects / Q000502:physiology; D051379:Mice; D009420:Nervous System / Q000196:embryology*; D054259:Neural Tube / Q000196:embryology; D055495:Neurogenesis / Q000187:drug effects / Q000235:genetics*; D009474:Neurons / Q000166:cytology / Q000378:metabolism; D017468:Receptors, Fibroblast Growth Factor / Q000819:agonists / Q000378:metabolism; D012097:Repressor Proteins / Q000235:genetics*; D015398:Signal Transduction / Q000187:drug effects / Q000235:genetics; D013234:Stem Cells / Q000166:cytology / Q000187:drug effects / Q000378:metabolism*; D051153:Wnt Proteins / Q000235:genetics / Q000494:pharmacology; D060508:Wnt3 Protein; D060509:Wnt3A Protein; D000074165:Zinc Finger E-box Binding Homeobox 2
C496457:Fgf8 protein, mouse; D018398:Homeodomain Proteins; D017468:Receptors, Fibroblast Growth Factor; D012097:Repressor Proteins; D051153:Wnt Proteins; D060508:Wnt3 Protein; D060509:Wnt3A Protein; C555511:Wnt3a protein, mouse; C120602:ZEB2 protein, mouse; D000074165:Zinc Finger E-box Binding Homeobox 2; D051524:Fibroblast Growth Factor 8; D005346:Fibroblast Growth Factors
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