Hdac8 contributes to HSC homeostasis and long-term CFC activity. (A) Relative expression levels of Hdac8 messenger RNA (mRNA) in sorted phenotypic HSPC and lineage populations (n = 2-7) assessed by SYBR Green–based quantitative reverse transcription polymerase chain reaction assays. Shown is the relative expression level (mean ± standard error of the mean [SEM]) for Hdac8 mRNA normalized to the Hprt mRNA expression level. (B) Schematic of experimental design (left). Mx1-Cre/Hdac8^f/f(y) or controls (WT, Hdac8^f/f(y), or Mx1-Cre) were injected with 7 doses (14 mg/kg) of poly (I:C) to induce the expression of Cre. Phenotypic analysis of HSPCs and CFC assays were performed 6 weeks after induction. Hdac8 protein levels in induced Mx1-Cre/Hdac8^f/f(y) (Hdac8^Δ/Δ) or control (Ctrl) BM cells shown by western blotting using Hdac8 specific antibody (right). (C) Frequency of various lineage populations in 2- to 3-month-old Hdac8^Δ/Δ (n = 7) or Ctrl (n = 15) BM assessed by fluorescence-activated cell sorting. (D) Frequency of LT-HSC, short-term HSC (ST-HSC), and MPP subsets in Hdac8^Δ/Δ (n = 10) or Ctrl (n = 13-19) BM. (E) Frequency of LSK, myeloid/erythroid progenitor populations in Hdac8^Δ/Δ (n = 10) or Ctrl (n = 13-19) BM. (F) Number of CFU-Cs derived from Hdac8^Δ/Δ or Ctrl BM cells (1 × 10⁴ cells) in serial replating assays every 7 days. Shown is mean ± SEM with triplicates from 2 independent experiments. (G) The percentage of CFU-GEMM, CFU-GM, and BFUE colony types determined based on morphology. Shown is mean ± SEM with triplicates from 2 independent experiments. (H) Number of pre-B CFU-Cs derived from Hdac8^Δ/Δ or Ctrl BM cells (1 × 10⁴ cells). Shown is mean ± SEM. *P < .05, **P < .01, ***P < .001.