Ikaros-induced gene expression changes relating to V(D)J recombination. (A) Symbols as in Figure 3. (B) RT-PCR validation of Ikaros-induced gene expression changes related to V(D)J recombination in B3 cells (mean ± SD; n = 3 independent biological replicates; * P < .05, ** P < .01, *** P < .001; Student t test). (C) RT-PCR validation of Aiolos-induced gene expression changes related to V(D)J recombination in B3 cells (mean ± SD; n = 3 independent biological replicates; ** P < .01, *** P < .001; Student t test). (D) RT-PCR validation of Ikaros-induced gene expression changes related to V(D)J recombination in primary pre-B cells (mean ± SD; n = 3 independent biological replicates; * P < .05, ** P < .01; Student t test). (E) Model for the regulation of Rag1 and -2 through an Ikaros-based feed-forward loop involving Foxo1. Note that the design of feed-forward loops introduces a time delay so that not all targets of an upstream transcription factor will respond immediately to its expression. The model includes the Ikaros-regulated gene Gfi1b, which negatively regulates Rag expression both directly and indirectly through repression of Foxo1.