Tip60 is essential for adult HSC maintenance in a cell-intrinsic manner. (A) Male 6- to 10-week-old Tip60^f/f, Tip60^f/+; Mx1-Cre, and Tip60^f/f; Mx1-Cre mice were injected with pIpC for 3 consecutive days. BM cells were analyzed for the frequency of HSPCs by flow cytometry 5 days after the last injection: LSK (Lin⁻c-Kit⁺Sca-1⁺), LK (Lin⁻c-Kit⁺Sca-1⁻), HSC (CD34, CD34⁻Flk2⁻; SLAM, CD150⁺CD48⁻LSK), ST-HSC (CD34, CD34⁺Flk2⁻; SLAM, CD150⁻CD48⁻LSK), MPP (CD34, CD34⁺Flk2⁺; SLAM, CD150⁻CD48⁺LSK), GMP (CD34⁺CD16/32⁺LK), CMP (CD34⁺CD16/32⁻LK), MEP (CD34⁻CD16/32⁻LK), and CLP (Lin⁻IL7R⁺c-Kit⁺Sca1⁺Flk2⁺). Representative dot plots and frequencies of the HSPC subpopulation from Tip60^f/f, Tip60^+/Δ, and Tip60^Δ/Δ mice are shown. (B) The absolute number of HSPCs and WBM cells from Tip60^f/f, Tip60^+/Δ, and Tip60^Δ/Δ mice is shown. (C) WBM cells (1 × 10⁶) from control Tip60^f/f and Tip60^Δ/Δ mice (CD45.2⁺) were transplanted into lethally irradiated recipient mice (CD45.1⁺), along with 2 × 10⁵ congenic WBM cells (CD45.1⁺CD45.2⁺). Donor chimerism of recipient PB is shown. (D) Donor chimerism of recipient BM HSCs (CD150⁺CD48⁻LSK) at 16 weeks after transplantation. (E) CFSE-labeled HSCs were injected into lethally irradiated congenic mice, and homing efficiency was analyzed 16 hours after the injection (n = 3). (F) WBM cells (1 × 10⁶) from Tip60^f/f or Tip60^f/f; Mx1-Cre mice (CD45.2⁺) (left) were transplanted into lethally irradiated recipient mice (CD45.1⁺) along with 2 × 10⁵ congenic WBM cells (CD45.1⁺CD45.2⁺). WBM cells (5 × 10⁵) from Tip60^f/f or Tip60^f/f;Mx1-Cre mice (CD45.2⁺) (right) were transplanted into lethally irradiated recipient mice (CD45.1⁺), along with 5 × 10⁵ congenic WBM cells (CD45.1⁺CD45.2⁺). pIpC was injected into the recipients 6 weeks after transplantation. Donor chimerism in all nucleated cells of recipient PB are shown. Values are presented as means ± standard error of the mean. Statistical analyses were performed vs Tip60^f/f. *P < .05; **P < .01; ***P < .001; ns; not significant