Figure 1. Sin1 regulates B cell development.

a) Bone marrow from Sin1^+/+ or Sin1^-/- chimeric mice was analyzed by flow cytometry and the percentage of CD19⁺ IgM^- and CD19⁺ IgM⁺ B cells is indicated. The data are representative of Sin1^+/+ (n=3) and Sin1^-/- (n=4) fetal liver chimeric mice.

b) Bone marrow from a chimeric mouse containing a 1:1 ratio of wild type host and Sin1^-/- donor cells was analyzed by flow cytometry. The plots shown are pre-gated on CD45.1⁺ host cells or CD45.1^- Sin1^-/- donor cells and the percentage of CD19⁺IgM^- and CD19⁺IgM⁺ B cells is indicated.

c) Bar graph illustrating the total number of Sin1^+/+ host or Sin1^-/- donor bone marrow cells from the chimeric mouse shown in (b).

d) The proportion of B220⁺CD43^hiIgM^- bone marrow pro-B cells from wild type or Sin1^-/- fetal liver chimeric mice. The plots shown are pre-gated on CD45.2⁺ donor cells and are representative of Sin1^+/+ (n=3) and Sin1^-/- (n=4) fetal liver chimeric mice.

e) Sin1^+/+ or Sin1^-/- pro-B cells were cultured in vitro on OP9 cells with or without IL-7 for 7 days and surface IgM and IgD expression was analyzed. The plots are representative of 4 independent experiments.

f) Sin1^+/+ or Sin1^-/- pro-B cells were cultured on OP9 cells without IL-7 for 7 days, fixed, permeablized and stained for Igμ chain expression (shaded area). The proportion of Igμ^- pro-B cells is indicated. Rag1^-/- pro-B cells are a negative control for Igμ staining (dotted line). Representative plots are shown from 3 independent experiments.