The IFN-g and TH2 loci are colocalized in the nucleus detected by fluorescence in situ hybridization (FISH).
Hybridization of naïve T cells, TH1 cells and TH2 cells, with rhodamine-dUTP labeled BAC clone for the TH2 locus and spectrum green-dUTP labeled BAC clone for the IFN-g locus. The first column of photomicrographs (100X) represents DAPI staining of the nuclei for the presence of DNA. For each cell type two situations are represented where the two spots representing the two alleles of a locus are completely separate, or one allele of each locus is colocalized with one allele of the other locus and the second is not. The experiments were done to determine the relative localization of the Ifng and the TH2 cytokine gene loci. Signals with a relative distance of ≤5 pixels were scored as colocalized for all cell types. All cells for each category were scored blindly and slides were prepared from two different preparations of cells.
Our study shows that there is a direct interchromosomal interaction between two loci that are expressed as mutually exclusive alternatives in two different cell types. TH1 cells express IFN-g and TH2 cells express IL-4, IL-5 and IL-13, the latter three residing as linked genes in the TH2 cytokine locus and are coordinately regulated by the action of the TH2 LCR and other cis elements. The colocalization of the Ifng with the TH2 locus was established with the 3C technique and confirmed with FISH experiments.
Figure and legend courtesy of Richard Flavell.
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