Mouse adult hematopoietic stem cells actively synthesize ribosomal RNA

Flow-FISH allows quantification of pre-rRNA levels during erythroid differentiation. BM cells were stained using Flow-FISH with probes directed against its1 or its2 or a scramble control probe (scr). (A) FACS profile of FISH levels in the whole BM population of samples stained with either no probe (gray) or the scr (blue) and its2 (red) probes. (B) Quantification of its1 and its2 levels in cells of the erythroid lineage, relative to its1 and its2 levels in the BM population: pro-erythroblasts (proE, CD71⁺ Ter119^low), basophilic erythroblasts (basoE, CD71⁺ Ter119⁺), late basophilic and polychromatophilic erythroblasts (polyE, CD71^low Ter119⁺), and orthochromatophilic erythroblasts (orthoE, CD71⁻ Ter119⁺). For comparisons of pre-rRNA levels between BM and erythroid populations of samples stained with the same probe, statistical significance was calculated using one-way ANOVA with Dunnett's correction for multiple comparisons: (†) P < 0.05, (††) P < 0.01, (†††) P < 0.001. n = 3 mice; representative results of four independent experiments.