Figure 4. Phosphorylated SRF activates a gene program that in concert with AP-1 at Group 1 enhancers promotes the preferential growth in width of adult rat ventricular myocytes.

A, Volcano plot showing genes significantly upregulated (green, n = 1,101) or downregulated (red, n = 962) with a false discovery rate < 0.05 in PRO-seq for myocytes treated for 1 hour +/− 20 μmol/L phenylephrine (PE). B, Volcano plot showing myocyte genes significantly upregulated (green, n = 287) or downregulated (red, n = 289) with a false discovery rate < 0.05 in PRO-seq by expression of Flag-tagged SRF S103D in comparison to control Flag-SRF WT protein. C, Heatmap showing fold-change (Log₂) expression due to PE treatment or Flag-SRF S103D or S103A expression as assayed by PRO-seq for the PE-regulated genes in A. D, Network of genes upregulated by both PE and S103D expression analyzed by Cytoscape.⁴⁰ Each term is represented by a circle node, where its size is proportional to the number of input genes falling into that term, and its color represents its cluster identity. Terms with a similarity score > 0.3 are linked by an edge, and the thickness of the edge represents the similarity score. E, HOMER motif analysis of the enhancers in Groups 1-3 showing the most enriched motifs for the different Groups as present in each Group. F, Myocytes transfected with control (Cont) siRNA or siRNA for individual AP-1 family members were cultured for 24 hours +/− 20 μmol/L PE before morphometric assay (Cf. Figure X in Data Supplement). Representative polarized light microscopy images are shown. Bar - 25 μm. Bars and colored symbols indicate average mean and means of independent experiments using different myocyte preparations, respectively. Data analyzed by matched two-way ANOVA and Tukey post-hoc testing. ^† vs. no drug for same siRNA; * vs. control siRNA under the same treatment condition; n = 4. *,^† p < 0.05; ^††† p < 0.001.