Deletion of all three piwi genes causes increased HSC frequency, but does not affect progenitor or committed cell type numbers.

<p>Piwi-triple-knockout mature blood cell numbers are unchanged compared to control mice (WT, HET), as determined by (A) Complete Blood Cell Count (CBC) for white blood cells (WBC), neutrophils (NE), lymphocytes (LY), red blood cells (RBC) and (B) FACS analysis of committed bone marrow cell types (A: WT, n = 3; HET, n = 4; triple KO, n = 4; B: WT, n = 2; HET, n = 3, triple KO, n = 3). (C) Colony Forming Unit (CFU) assays show similar total myeloid/erythroid progenitor-derived colony numbers in control and triple <i>Piwi</i> mutant bone marrow. Colony assays used total bone marrow from 3 individual mice for each genotype. Bone marrow samples were plated in triplicate and total colonies were counted at days 7–10. Data shown as the average total colony count for each genotype. (D) In the triple <i>Piwi</i> mutant, the percentage of bone marrow progenitors (CMP, MEP and GMP) are only moderately increased compared to control mice progenitors. (E) HSC percentages are significantly increased in <i>Piwi</i> triple knockout bone marrow. (F) Total bone marrow cellularity of the triple knockout mice is almost two-fold reduced compared to control mice. (C-F: Control, n = 4; triple KO, n = 4). <i>P</i> values calculated using two-tailed, unequal variance Student's <i>t</i> test.