MegP transcriptome was distinct from those of other HSPCs. (A) Gene expression profiling of BM-derived HSPCs analyzed by microarray. Unsupervised hierarchical clustering analysis on differentially expressed genes among analyzed populations is shown in the dendrogram together with a heat map representing gene expression level by color (top). The thick pink line demarcates 5 distinct clusters (C1-C5). C2, C3, and C5 genes were upregulated in lineage-committed HPCs (GMPs, MegPs, and MEPs, respectively). The biological meanings of C1-C5 cluster genes were investigated using the Database for Annotation, Visualization and Integrated Discovery tool, and results are listed in the table (bottom). (B-D) Gene expression patterns of hematopoietic lineage-affiliated gene sets are shown in heat map displays. MegPs predominantly expressed megakaryocyte-specific genes. The following two gene sets were obtained from the Molecular Signatures Database: (i) REACTOME PLATELET ACTIVATION SIGNALING AND AGGREGATION and (ii) REACTOME PLATELET ADHESION TO EXPOSED COLLAGEN. Ery, erythroid.