BM progenitor phenotype and cell cycle status in jam-b deficient mice. (A) The cellularity, number, and frequency of Lin^Neg progenitor cells in the bone marrow of jam-b deficient (black bar) or control mice (white bar) are shown. Results are expressed as mean ± SD. (B) Numbers and frequencies of LSK, CMP, and GMP cells in jam-b deficient (black bar) compared with control mice (white bar) are shown. (C) Colony-forming assays with jam-b deficient (black bar) compared with control mice (white bar). Results are expressed as number of CFU-C per 1000 cells. (D) Left panels: Representative flow cytometry profiles showing the gating strategy used to define LT-HSC. Right panels: Percentage of LT-HSC within the Lin^Neg population and absolute numbers of LT-HSC are shown. The decreased frequency of LT-HSC observed in jam-b^−/− mice does not translate in changes in absolute numbers. (E) Representative dot-plots showing ki-67/DAPI staining gated on LSK cells (top panels) or on HSC-MPP (bottom panels) are shown. The graphs show the frequencies of LSK or HSC-MPP1 cells in Phase G₀ (Ki-67^Neg DAPI^Neg), G₁ (Ki-67^Pos DAPI^Neg), and S/G₂/M (Ki-67^Pos DAPI^Pos) in jam-b−/− mice (black bar) compared with control mice (white bar). Decreased frequencies of progenitor cells in G₀ Phase are observed in jam-b^−/− mice. (F) The levels of bone marrow SDF-1α contents in jam-b^−/− (black bar) or control mice (white bar) assessed by ELISA are shown. Results are expressed as SDF-1α concentration and correspond to the SDF-1α quantity found in 1 leg. (G) Representative histogram profiles showing CXCR4 expression on the indicated hematopoietic subset in control (gray line) and jam-b deficient mice (filled profile). Graphs in the left panels show the percentages and the MFI of CXCR4 expression on the indicated subset in control (white bar) and jam-b deficient mice (black bar). Results are representative of at least 5 mice per group (*P < .05; **P < .01; ***P < .001).