MK maturation and platelet count are suppressed in SRGN^–/– mice. (A) Platelet count was determined by complete blood count from mice (WT, n = 8; SRGN^–/–, n = 9). (B) Mean platelet volume (WT, n = 8; SRGN^–/–, n = 9). (C) The number of CD41⁺/CD42b⁺ bone marrow–derived cells; n = 10. (D) The percentage of CD41⁺/CD42b⁺ cells that reside within the indicated ploidy peak after propidium iodide staining; n = 3. (E) CD45⁺Lin^–CD41⁺CD42d⁺ and (F) CD45⁺Lin^–Sca-1^–c-Kit⁺CD150⁺CD41⁺ bone marrow cell counts as determined by flow cytometry (n = 5). (G) MK⁺ colonies produced from pooled bone marrow and assessed by acetylcholinesterase detection (n = 8). All experiments were performed with samples from 52-week-old mice. Significance: ns is indicated by P > .05; ∗P ≤ .05; ∗∗P ≤ .01; ∗∗∗P ≤ .001; ∗∗∗∗P ≤ .0001. All error bars represent the SEM. CFUs, colony-forming units. K/μL, thousands per microliter.