Determining the Compaction State of Genes Using DNA FISH

DNA fluorescence in situ hybridization (FISH) enables the visualization of chromatin architecture and the interactions between genomic loci at a single-cell level, complementary to genome-wide methods such as Hi-C. DNA FISH uses fluorescent-labeled DNA probes targeted to the loci of interest, allowing for the analysis of their spatial positioning and proximity with microscopy. Here, we describe an optimized experimental procedure for DNA FISH, from probe design and sample preparation through imaging and image quantification. This protocol can be readily applied to querying the spatial positioning of genomic loci of interest.