Nodal/Activin Signaling in ES Cell Fate Decisions Figure 3. Increased and Decreased Nodal/Activin Signaling Leads to Transcriptional Regulation of Specific Subsets of Target Genes. (A) Heatmap showing microarray analysis of ES cells after 18 hours treatment with Activin (ACT), SB or DMSO vehicle control in KSR media. Transcript levels are expressed as log2 fold change over the average of DMSO controls with red showing upregulation and green showing downregulation in n = 4 biological replicates from passage numbers 20 to 24 (P20-P24). Highlighted gene names indicate known roles or domains of expression in endoderm (red), mesoderm (blue), trophectoderm (green) or cancer (magenta). Color bar shows fold change in gene expression on a log2 scale. (B) RT-PCR validation of target genes identified in the microarrays that are specifically regulated in ACT and/or SB treatments compared to the DMSO control. Ywhaz was used as a housekeeping control. doi:10.1371/journal.pgen.1002130.g003 PLoS Genetics | www.plosgenetics.org 7 June 2011 | Volume 7 | Issue 6 | e1002130