Cebpa enhancer deletion causes neutropenia and reduction in LT-HSCs of +37kb^HOM BMs. (A-B) Representative flow cytometry plots showing Mac1+Gr1+ myeloid cell populations in PB (A) and BM (B) of +37kb^WT (blue), +37kb^HET (green), and +37kb^HOM (red) mice. (C) Absolute numbers of Mac1+Gr1+ cells calculated from total PB counts of 37kb^WT (blue), +37kb^HET (green), and +37kb^HOM (red) mice. (D) Relative numbers of total Mac1+Gr1+ cells calculated from total BM cell count from 1 femur, corrected for body weight in grams of each mouse. (E) Hematoxylin and eosin (H&E) staining of representative cross sections showing BM architecture (left), identifying megakaryocytes (right [arrows]) in +37kb^WT and +37kb^HOM mice. (F) S100A8 immunohistochemical staining of representative BM cross sections from 37kb^WTand +37kb^HOM mice. (G) Representative flow cytometry plots of LK, LSK, LT-HSC, ST-HSC, MPP3, MPP2 cell populations in BM of 37kb^WT, +37kb^HET, and +37kb^HOM mice. (H) Absolute numbers of CD150+CD48- LT-HSCs calculated from total BM cell counts from 1 femur. All data are represented as mean +/− SD. Statistical significance was calculated using a Student t-test. *P value < .05; **P value < .005; ***P value < .0005; N.S., not significant; SD, standard deviation; LK, Lineage- cKit+; LSK, Lineage- Sca1+ cKit+; LT-HSC, long-term hematopoietic stem cell; ST-HSC, short-term hematopoietic stem cell; MPP, multipotent progenitor; +37kb^WT, wild type +37kb enhancer; +37kb^HET, heterozygous +37kb enhancer deletion; +37kb^HOM, homozygous +37kb enhancer deletion.