Ikaros-induced gene expression changes relating to pre-BCR signaling. (A) Schematic representation of genes in the pre-BCR signaling pathway. Genes are in italics and the corresponding proteins are listed where they are better known than the genes. The cell membrane, nuclear membrane, and the pre-BCR are outlined. Orange, gold, and yellow mark significant mRNA expression changes at the indicated times and an asterisk shows that expression changes have been verified by quantitative reverse transcription-polymerase chain reaction (RT-PCR). Genes with a black outline are bound by Ikaros in ChIP experiments (±2 kb, see below). A gray background marks pathway components that did not change expression. (B) RT-PCR validation of Ikaros-induced gene expression changes related to pre-BCR signaling 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 pre-BCR signaling in B3 cells (mean ± SD; n = 3 independent biological replicates; * P < .05, ** P < .01, *** P < .001; Student t test). (D) RT-PCR validation of Ikaros-induced gene expression changes related to pre-BCR signaling in primary pre-B cells (mean ± SD; n = 3 independent biological replicates; * P < .05, ** P < .01, *** P < .001; Student t test). The quantitative differences between Ikaros effects in B3 cells vs primary pre-B cells are due to the lower level of Ikaros expression achieved in primary pre-B cells (not shown). (E) Ikaros controls the expression of Syk, a key kinase upstream of SLP65 (encoded by Blnk) and thereby directs pre-BCR (or BCR-ABL) signals toward SLP65.