Mouse adult hematopoietic stem cells actively synthesize ribosomal RNA

RNA Pol I inhibitors lead to significant decrease of pre-rRNA levels detected by Flow-FISH. BM cells were incubated or not in the presence of 10 µM CX-5461 or 2.5 µM BMH-21 for 3 h, and were then stained using Flow-FISH with probes directed against its1 or its2 or a nontargeting probe (scr). Quantification of its1 (A) and its2 (B) levels in the indicated populations, relative to levels in the BM population (HSC: Lin^– Sca1⁺ cKit⁺ CD34^–; MPP: Lin^– Sca1⁺ cKit⁺ CD34⁺; CMP: Lin^– Sca1⁺ cKit⁺ CD34^hi; GMP: Lin^– Sca1⁺ cKit⁺ CD34^lo; MEP: Lin^– Sca1⁺ cKit⁺ CD34^lo). Statistical significance of the differences between treated and untreated cells was calculated using unpaired two-tailed Student's t-tests: (*) P < 0.05, (**) P < 0.01, (***) P < 0.001, (****) P < 0.0001. n = 3 mice for each sample group.