BAF53a is essential for BM HSC and progenitor cell proliferation and survival. (A) In vivo BrdU incorporation assays of total BM cells (top panel) and myeloid progenitors (Mac1⁺Gr1⁺; bottom panel) in pIpC-treated BAF53a^fl/flCre⁺ animals (15-hour pulse). Representative images are shown. (B) Proportion of BrdU⁺ LT-HSCs, HSC-enriched Sca1⁺Lin⁻ cells, myeloid progenitors (Mac1⁺Gr1⁺), and total BM cells in pIpC-treated BAF53a^fl/flCre⁺ mice (days 5-7). (C) Cell-cycle distribution of total BM cells (top panel) and myeloid progenitors (Mac1⁺Gr1⁺; bottom panel) in pIpC-treated mice. Hoechst 333342 staining (DNA content) was performed on day 7 after pIpC treatment. Representative profiles are shown. (D) Quantitative analysis of apoptosis in the HSC-enriched Sca1⁺Lin⁻ population (left panel), myeloid progenitors (Mac1⁺Gr1⁺; right panel), and total BM cells (bottom panel). TUNEL was performed on days 4-8 after pIpC treatment as indicated. Data are mean ± SD; n = 4 per genotype. **P ≤ .01 (Student t test).