SABER enables highly multiplexed and amplified detection of DNA and RNA in cells and tissues

Fluorescent in situ hybridization (FISH) reveals the abundance and positioning of nucleic acid sequences in fixed samples and can be combined with cell segmentation to produce a powerful single cell gene expression assay. However, it remains difficult to label more than a few targets and to visualize nucleic acids in environments such as thick tissue samples using conventional FISH technologies. Recently, methods have been developed for multiplexed amplification of FISH signals, yet it remains challenging to achieve high levels of simultaneous multiplexing combined with high sampling efficiency and simple workflows. Here, we introduce signal amplification by exchange reaction (SABER), which endows oligo-based FISH probes with long, single-stranded DNA concatemers that serve as targets for sensitive fluorescent detection. We establish that SABER effectively amplifies the signal of probes targeting nucleic acids in fixed cells and tissues, can be deployed against at least 17 targets simultaneously, and detects mRNAs with high efficiency. As a demonstration of the utility of SABER in assays involving genetic manipulations, we apply multiplexed FISH of reporters and cell type markers to the identification of enhancers with cell type-specific activity in the mouse retina. SABER represents a simple and versatile molecular toolkit to allow rapid and cost effective multiplexed imaging.