Ikaros targets in pre-B cells and genes differentially expressed during lymphoid lineage specification and differentiation in vivo share biological pathways. Circles represent up- and down-regulated genes during the in vivo differentiation of MLPs to CLPs, B-cell lineage specification (CLP to Fr.A pro-B cells), T-cell lineage differentiation (CLP to DP thymocytes), and the transition from proliferating to resting pre-B cells (Fr. C' to Fr. D; www.immgen.org). The proportion of these in vivo gene sets that are regulated (intermediate shading) or bound and regulated by Ikaros in B3 cells (dark shading) is shown for the indicated time points. Enriched biological pathways (P < .05) were derived from genes that are differentially expressed in vivo and that are bound and regulated by Ikaros in B3 cells (P < .05). The network of Ikaros-interacting transcription factors depicted at the center of the scheme is based on the literature^17,18,33,45  and data described here.