Deletion of Phf6 in steady-state hematopoiesis. (A) Competitive reconstitution assays using the CreERT system. BM cells from 8-week-old CreERT and CreERT;Phf6^fl/y mice were transplanted into lethally irradiated recipient mice with the same number of competitor BM cells (5 × 10⁶ cells). Four weeks after transplantation, recipient mice were injected with tamoxifen (TM) for 5 consecutive days. Serial transplantations were performed as described in Figure 2E. PB analyses were performed every 4 weeks and a BM analysis was performed 16 weeks after the tamoxifen injection. (B) The chimerism of CD45.2⁺ donor-derived cells in the PB of recipient mice is shown (n = 5 or 6). (C) The chimerism of My, B-, and T-cell lineages in PB and those of HSCs and progenitors at 16 and 32 weeks after 1° transplantation are shown (n = 5 or 6). (D-F) Spleen weight (D), spleen cell number (E), and the number of LSK cells in the spleen (F) 16 and 32 weeks after 1° transplantation are shown (n = 5). (G) Growth of CE and CE;Phf6^Δ/y CD150⁺CD34⁻LSK HSCs in vitro. Freshly sorted HSCs were cultured under HSC culture conditions (SCF+TPO) for 14 days (n = 3). During the culture, cells were treated with 200 nM 4-hydroxytamoxifen (4-OHT) for 16 hours from 24 hours after cell sorting to induce the CreERT-mediated excision of Phf6. Data are shown as the mean plus or minus SEM. *P < .05, **P < .01, ***P < .001 by the Student t test.