KappaBle fluorescent reporter mice enable low-background single-cell detection of NF-κB transcriptional activity in vivo

Nuclear factor-kappa B (NF-kappa B) is a transcription factor with a key role in a great variety of cellular processes from embryonic development to immunity, the outcome of which depends on the fine-tuning of NF-kappa B activity. The development of sensitive and faithful reporter systems to accurately monitor the activation status of this transcription factor is therefore desirable. To address this need, over the years a number of different approaches have been used to generate NF-kappa B reporter mice, which can be broadly subdivided into bioluminescence- and fluorescence-based systems. While the former enables whole-body visualization of the activation status of NF-kappa B, the latter have the potential to allow the analysis of NF-kappa B activity at single-cell level. However, fluorescence-based reporters frequently show poor sensitivity and excessive background or are incompatible with high-throughput flow cytometric analysis. In this work we describe the generation and analysis of ROSA26 knock-in NF-kappa B reporter (KappaBle) mice containing a destabilized EGFP, which showed sensitive, dynamic, and faithful monitoring of NF-kappa B transcriptional activity at the single-cell level of various cell types during inflammatory and infectious diseases.