(A) Promoter motif enrichment in genes upregulated in miR-1 double-knockout hearts. Motif sequences and transcriptional regulators are indicated (left) with the log10 of the hypergeometric p value graphed. Multiple CArG box sequences, the motif bound by SRF, were identified (red). (B) Western blot (top), and qPCR (bottom) for Srf expression in post-natal miR-1 null or wild-type hearts. (C) Myocardin dependent and independent SRF target gene expression in postnatal miR-1 null or wild-type hearts by qPCR (left). Western blots of selected Myocardin-dependent SRF target genes (right). Tagln, Transgelin/Sm22; Csrp1,2, Cysteine And Glycine-Rich Protein 1,2; Cnn1,2, Calponin1,2; Acta2, smooth muscle alpha actin; miR-145, microRNA-145; Fos, FBJ Murine Osteosarcoma Viral Oncogene Homolog; Egr1, Early growth response 1. *p<0.05; **p<0.01; ***p<0.001;****p<0.0001; ns, not significant.