Gene Expression
Elucidating Regulators of Stem Cell Differentiation and Cardiac Tissue Formation
A review of Sox17 is essential for the specification of cardiac mesoderm in embryonic stem cells.
Note: This is a review of the published article listed below. All information, quotes, figures, methods, and findings mentioned in this review are from that article, and are the property of its authors and/or the publication in which the article originally appeared.
Liu et al (2007) use gene expression analysis to show that the Wnt/β-catenin pathway is essential for cardiac myogenesis to occur in embryonic stem (ES) cells, acting at a gastrulation-like stage to mediate mesoderm formation and patterning (two prerequisites for cardiac myogenesis itself). Among the temporally associated genes identified by the research team was Sox17, which was found to encode an endodermal HMG-box transcription factor. Microarray analysis (using 22K mouse 60-mer arrays from Agilent, in part) of Wnt- and BMP-dependent genes in differentiating ES cells enabled the team to identify multiple early targets and lentiviral vectors for RNA interference in differentiating ES cells in order to characterize an essential role for Sox17 in cardiac muscle cell formation. Data demonstrated that Sox17 short hairpin RNA suppressed cardiac myogenesis selectively, acting subsequent to mesoderm formation yet before induction of Mesp1 and Mesp2, a pair of related basic helix–loop–helix transcription factors that together are indispensable for creating heart mesoderm. Sox17 short-hairpin RNA blocks cardiac myogenesis non-cell autonomously and impairs the induction of Hex, a homeodomain transcription factor that is known to be required for the production of endoderm-derived heart-inducing factors. Beyond its impact on fundamental knowledge of ES cell differentiation, dissecting the Sox17-dependent pathway for cardiac mesoderm specification may have applied significance, if used to help drive ES cells to a cardiac fate.
Figure 1. Microarray analysis of Wnt- and BMP-dependent genes in differentiating ES cells identifies multiple early targets.
(A) Partial cluster analysis of genes fulfilling the criteria of developmental regulation plus modulation by both sFz8 and Noggin at >1 days. Genes shown were chosen from the significantly inhibited GeneOntology and GenMAPP clusters, Entrez Gene entries, PubMed, and Mouse Genome Informatics database. The neurogenesis cluster shown for comparison in c, below, is taken from the developmentally up-regulated genes whose induction was enhanced by sFz8 and Noggin. n = 4 for 0–3 d; n = 2 for 5–9 d. (B) QRT-PCR confirmation of selected day three findings as contingent on canonical Wnts.
Figure 2. Regulation of Sox17 in differentiating ES cells by the canonical Wnt pathway.
(A–C) QRT-PCR. n >3; *, P < 0.05 vs. control cells. (A) sFz8 and Noggin suppress Sox17 in differentiating ES cells. (B) Wnt3a up-regulates Sox17. (C) BIO rescues Sox17 from repression by sFz8. (D) Immunoblotting for epitope-tagged Sox17 and Sox18, showing efficacy and specificity of Sox17 shRNAs.
Title: : Sox17 is essential for the specification of cardiac mesoderm in embryonic stem cells.
Journal: PNAS, March 6, 2007 Vol. 104(10):3859-3864.
Authors: Liu Y, Asakura M, Inoue H, Nakamura T, Sano M, Niu Z, Chen M, Schwartz RJ, and Schneider MD.
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