Combined 3D DNA FISH, Single-Molecule RNA FISH, and Immunofluorescence.

Nuclear architecture is a potential regulator of gene expression in eukaryotic cells. Studies connecting nuclear architecture to gene expression are often population-averaged and do not report on the cell-level heterogeneity in genome organization and associated gene expression. In this report we present a simple way to combine fluorescence in situ hybridization (FISH)-based detection of DNA, with single-molecule RNA FISH (smFISH) and immunofluorescence (IF), while also preserving the three-dimensional (3D) nuclear architecture of a cell. Recently developed smFISH techniques enable the detection of individual RNA molecules; while using 3D DNA FISH, copy numbers and positions of genes inside the nucleus can be interrogated without interfering with 3D nuclear architecture. Our method to combine 3D DNA FISH with smFISH and IF enables a unique quantitative handle on the central dogma of molecular biology.