In vivo function of Lrf in HSCs. (A) Lrf knockout mice were challenged with 5-FU 9 days after the first pIpC injection and LT-HSC recovery was examined at indicated times. Graph shows absolute numbers of LT-HSCs after 5-FU treatment over time. Horizontal black bars: average value; error bars: standard deviation. (B) In Zbtb7a^Flox/FloxMx1-Cre⁺ mice, 5-FU–resistant dormant HSCs differentiate toward the T-cell lineage rather than self-renewing in response to the myeloablative stress. (C) Schematic representation of bone marrow transplantation (BMT). Fifty double-sorted LT-HSCs were transplanted into lethally irradiated CD45.1 recipient mice. (D) Shown are time-course follow-up of recipients' PB counts [myeloid (Gr1⁺CD11b⁺), B (B220⁺), and T cells (CD4⁺ or CD8⁺)]. Error bars: standard deviation. (E) BM hematopoiesis was followed up to 18 months after the last pIpC injection. Representative FACS profiles of hematopoietic development in BM and spleen analyzed 1 year after the last pIpC injection in control (Zbtb7a^Flox/FloxMx1-Cre⁻) and Lrf knockout (Zbtb7a^Flox/FloxMx1-Cre⁺) mice. BM DP T-cell development, B-cell differentiation block, normal myeloid development, and an anemia phenotype in spleen²¹  were evident in Lrf knockout mice.