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Global analysis of the transcriptional network controlling Xenopus endoderm formation

ABSTRACT: A conserved molecular pathway has emerged controlling endoderm formation in Xenopus zebrafish and mice. Key genes in this pathway include Nodal ligands and transcription factors of the Mix-like paired homeodomain class, Gata4-6 zinc finger factors and Sox17 HMG domain proteins. While a linear epistatic pathway has been proposed, the precise hierarchical relationships between these factors and their downstream targets are largely unresolved. Here we used a combination of microarray analysis and loss-of-function experiments to examine the global regulatory network controlling Xenopus endoderm formation. We identified over 300 transcripts enriched in the gastrula endoderm, including most of the known endoderm regulators as well as over a hundred uncharacterized genes. Surprisingly only 10% of the endoderm transcriptome is regulated as predicted by the current linear model. We find that Nodals, Mixer and Sox17 have both shared and distinct sets of downstream targets and that a number of unexpected autoregulatory loops exist between Sox17 and Gata4-6, Sox17 and Bix1, 2, 4 and between Sox17 and Xnr4. We find that Mixer does not function primarily via Sox17 as previously proposed. This data provides a new insight into the complexity of endoderm formation and will serve as valuable resource for establishing a complete endoderm gene regulatory network. Keywords: Embryonic, Development. Endoderm, Xenopus, nodal, Sox17, Mixer, microarray, gene regulatory network

ORGANISM(S): Xenopus laevis

PROVIDER: GSE4448 | GEO | 2006/03/11

SECONDARY ACCESSION(S): PRJNA94719

REPOSITORIES: GEO

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Project description:We show that high quality microarray gene expression profiles can be obtained following FACS sorting of cells using combinations of transcription factors. We use this transcription factor FACS (tfFACS) methodology to perform a genomic analysis of hESC-derived endodermal lineages marked by combinations of SOX17, GATA4, and CXCR4, and find that triple positive cells have a much stronger definitive endoderm signature than other combinations of these markers. Additionally, SOX17+GATA4+ cells can be obtained at a much earlier stage of differentiation, prior to expression of CXCR4+ cells, providing an important new tool to isolate this earlier definitive endoderm subtype. Overall, tfFACS represents an advancement in FACS technology which broadly crosses multiple disciplines, most notably in regenerative medicine to redefine cellular populations. 21 Total samples were analyzed. Samples collected after 5 days of hESC differentiation included SOX17+GATA4+ CXCR4+ cells, unfixed CXCR4+ cells, and unsorted fixed cells. Samples collected after 3 days of differentiation included SOX17+GATA4+ cells, SOX17-GATA- cells, and unsorted fixed cells. As controls, we analyzed both unfixed hESCs and fixed hESCs. All samples contained biological duplicates, triplicates or quadriplicates. We performed hierarchical clustering to demonstrate whether cellular fixation alone could change gene expression. We based this analysis on 1647 transcript clusters with coefficient of variation > 0.5 across the samples and expression values >= 500 in at least 2 out of the 21 samples. We found that fixation and staining steps did not cause distortions in gene expression measurements. This is supported by the fact that fixed and unfixed cells cluster together based upon differentiation stage, not based upon degree of fixation. Furthermore, using GSEA analysis, we found that the SOX17+GATA4+CXCR4+ day 5 cells and day 3 SOX17+GATA4+ were more enriched for compiled gold-standard endodermal genes than the CXCR4+ day 5 population.

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Global analysis of the transcriptional network controlling Xenopus endoderm formation

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