Comparisons of human and mouse expression data. A. Clustering of nine RNA-seq datasets using orthologous genes between human and mouse. Center panel: expression level heat map overview of 12168 orthologous genes. Expression level is measured in RPKM . The calculated number is increased by 1 to ensure valid logarithm transformation, and then log2 transformed. The sample tree on top is derived from Pearson's Correlation (PC) distance matrix, while the one at the bottom is derived from Euclidean Distance (ED) matrix. Both trees support the same topology, which grouped all neural stages with stem cell stage, while left muscle and liver in a separate group. Scale of color representation of the expression level is at the bottom of the figure. B. Scatter plot of orthologous gene expression level between selected stages. Genes without detectable expression were not included.