Project description:We showed that the Ikaros transcription factor is essential for the pre-B cell differentiation. We analyzed the transcriptome of a Ikaros deficient pre-B cell line which was reconstituted with an inducible Ikaros-ER fusion protein. To determine the direct Ikaros targets, we did ChIP-sequencing on chromatin from this pre-B cell line, as cell numbers in mice were too limiting for these studies.
Project description:Ikaros is important in the development and maintenance of the lymphoid system, functioning in part by associating with chromatin-remodeling complexes. We have studied the functions of Ikaros in the transition from pre-T cell to the CD4(+) CD8(+) thymocyte using an Ikaros null CD4(-) CD8(-) mouse thymoma cell line (JE131). We demonstrate that this cell line carries a single functional TCR ? gene rearrangement and expresses a surface pre-TCR. JE131 cells also carry nonfunctional rearrangements on both alleles of their TCR ? loci. Retroviral reintroduction of Ikaros dramatically increased the rate of transcription in the ? locus and TCR V?/J? recombination resulting in the appearance of many new ??TCR(+) cells. The process is RAG dependent, requires switch/sucrose nonfermentable chromatin-remodeling complexes and is coincident with the binding of Ikaros to the TCR ? enhancer. Furthermore, knockdown of Mi2/nucleosome remodeling and deacetylase complexes increased the frequency of TCR ? rearrangement. Our data suggest that Ikaros controls V?/J? recombination in T cells by controlling access of the transcription and recombination machinery to the TCR ? loci. The JE131 cell line should prove to be a very useful tool for studying the molecular details of this and other processes involved in the pre-T cell to ??TCR(+) CD4(+) CD8(+) thymocyte transition.