Genetic screen identifies cell type– and mouse strain–dependent microRNAs. (A) MicroRNA expression was evaluated in 4 developmentally related cell types isolated from the BM of C57BL/6 and DBA/2 mouse strains. (B) Hierarchical clustering was performed using the 147 quality-filtered probes (Euclidean distance, complete linkage). Samples are in columns, microRNAs in rows. For each probe, data were median-centered, with the lowest and highest intensity values in blue and red, respectively. Of each of the 8 microRNA signatures the average expression across cell types and mouse strains is shown (y-axis represents log2 expression ranging from −4 to 8). The number in the graphs indicates the number of microRNAs per signature. (C) Venn diagram showing the number of differentially expressed microRNAs between cell types and mouse strains. (D) An evolutionary conserved microRNA cluster, consisting of miR-99b, let-7e, and miR-125a, located on mouse chromosome 17. (E) Expression of miR-cluster 99b/let-7e/125a members across cell types and mouse strains (axes: as in panel B). Shown is the mean ± SD. (F) Paralogous microRNA clusters on chromosomes 9 and 16. (G) Expression of miR-100, miR-99a, and miR-125b across cell types and mouse strains (axes: as in panel B). For miR-125b only the cumulative expression of the chromosome 9 and 16 cluster could be assessed. Expression of let-7a and let-7c is not shown, as only the cumulative expression from multiple different genomic locations (including other chromosomes than 9, 16, and 17) could be assessed. Shown is the mean ± SD. LT indicates long-term; ST, short-term; CMP, common myeloid progenitor; MEP, megakaryocyte-erythrocyte progenitor; and GMP, granulocyte-macrophage progenitor.