Hdac8 deletion leads to loss of long-term serial repopulating activity in vivo. (A) Schematic of experimental design. Mx1-Cre/Hdac8^f/f(y)/mTmG⁺ (Hdac8^Δ/Δ) or Mx1-Cre/mTmG⁺ (control [Ctrl]) mouse (CD45.2⁺; 2-3 months old) BM cells (2 × 10⁵) were transplanted into lethally irradiated (11 Gy) CD45.1⁺ congenic recipients, along with CD45.1⁺ supporter BM cells (2 × 10⁵). Cre-mediated deletion of Hdac8 was induced in recipients by 7 doses of poly (I:C). Phenotypic HSPCs and GFP chimerism in the BM were analyzed 16 weeks after transplantation by flow cytometry. (B) Percentage of GFP⁺ donor chimerism in various lineage population at 16 weeks (n = 5-7). (C) Frequency of GFP⁺ donor-derived lineage populations 16 weeks after the first transplantation (n = 5-7). (D-E) The frequency of GFP⁺ donor-derived phenotypic HSPCs in the BM analyzed at 16 weeks (n = 5). (F) Frequency of GFP⁺ donor-cell repopulation over time (8-16 weeks). (G) The frequency of GFP⁺ donor-derived lineage populations in PB of secondary recipients (n = 3). (H) Frequency of GFP⁺ donor-derived cells in tertiary transplant recipients (Ctrl, n = 8; Hdac8^Δ/Δ, n = 4). Dashed line indicates 1%, above which is considered positive engraftment. (I) Phenotypic CD45.2⁺ LT-HSCs (200 cells) sorted from secondary recipient mice were transplanted along with CD45.1⁺ supporter BM cells (2 × 10⁵) into lethally irradiated (11 Gy) CD45.1⁺ congenic recipients. Frequency of Ctrl or Hdac8^Δ/Δ CD45.2⁺ donor-derived populations in the transplant recipients (Ctrl, n = 8; Hdac8^Δ/Δ, n = 5-6) over time. Mean ± SEM is shown. *P < .05, **P < .01, ***P < .001. IR, irradiation.