Figure 4. Genes with constrained expression.

(a) The distribution of the dynamic range (DNR, log₁₀ of the ratio of the largest and the lowest non-zero observation) of gene expression level in orthologous genes across human and mouse samples. (b) Venn diagram of the relationship between orthologous and constrained genes. (c) Proportion of nucleotides in expressed genes, as assessed by PolyA+ RNA-seq, that originates from constrained genes in human cell lines and mouse tissues. The labelled outliers correspond to mouse embryonic samples. (d,e) The distribution of DNR in human/mouse constrained and unconstrained genes in Merkin et al.10 (d) and Barbosa-Morais et al.9 (e). (f) The joint distribution of log₁₀ average gene reads per kilobase per million mapped reads (RPKM) in pairs of orthologous protein-coding genes; constrained genes are shown in red. (g) The distribution of promoter, transcript and protein pairwise sequence identity between human and mouse in constrained and unconstrained genes.