Modular structures within the transcriptional regulatory network. Yellow Triangles are the TFs and Red Circles are the target genes. (a) Clusters in the 98-gene and 153-TF network. (b) Cluster 6 contains 16 genes with a large set of common TF binding sites. (c) Cluster 1 showing potential co-regulation of Mef2c, Myf5, Irx5 by a common set of TF.