Effect of lenalidomide treatment on hematopoiesis in Crbn^I391Vmice. (A) Peripheral blood counts of WT and Crbn^I391V/I391V mice after 21 days of treatment with 50 mg/kg lenalidomide or vehicle. CD11b⁺ Gr1⁺ granulocyte and platelet data are pooled from 2 treated cohorts of mice treated for 21 to 24 days. n ≥ 3 for data shown, which are representative of 4 independent experiments. (B) Hematopoietic stem and progenitor cell compartments in WT and Crbn^I391V/I391V mice after 21 days of treatment with 50 mg/kg lenalidomide or vehicle. LK cells are Lineage⁻ c-Kit⁺; ST-HSC are Lineage⁻ c-Kit⁺ Sca1⁺ CD48⁻ CD150⁻; LT-HSC are Lineage⁻ c-Kit⁺ Sca1⁺ CD48⁻ CD150⁺. n ≥ 3 for data shown, which are representative of 3 independent experiments. Lineage markers are CD3, B220, CD11b, Gr1, and Ter119. (C) Hematopoietic progenitor compartments in WT and Crbn^I391V/I391V mice after 28 or 35 days of treatment with 50 mg/kg lenalidomide or vehicle. MPP are Lineage⁻ c-Kit⁺ Sca1⁺ CD48⁺ CD150⁻; CMP are Lineage⁻ c-Kit⁺ Sca1⁻ CD34⁺ CD16/32^mid; GMP are Lineage⁻ c-Kit⁺ Sca1⁻ CD34⁺ CD16/32^hi; MEP are Lineage⁻ c-Kit⁺ Sca1⁻ CD34⁺ CD16/32^low. Lineage markers are CD3, B220, CD11b, Ter119, and Gr1. n ≥ 5 for data shown, which are combined from 2 independent experiments. (D) Erythroid differentiation subsets as defined by CD71 and TER119 staining in the bone marrow from WT and Crbn^I391V/I391V mice after 28 days of treatment with vehicle or 50 mg/kg lenalidomide. n ≥ 4 for data shown, which are representative of 3 independent experiments. **P < .005. P values calculated using unpaired Student t test. Error bars are standard error of the mean. LSK, Lineage⁻ c-Kit⁺ Sca1⁺; ns, not significant; PLT, platelet; WBC, white blood cell.