Fbxo2VHC mouse and embryonic stem cell reporter lines delineate in vitro-generated inner ear sensory epithelia cells and enable otic lineage selection and Cre-recombination

Abstract

While the mouse has been a productive model for inner ear studies, the lack of highly specific genes and tools have presented challenges, specifically for in vitro studies of otic development, where innate cellular heterogeneity and disorganization increase the reliance on lineage-specific markers. To address this challenge in mice and embryonic stem (ES) cells, we targeted the lineage-specific otic gene Fbxo2 with a multicistronic reporter cassette (Venus/Hygro/CreER = VHC). In otic organoids derived from ES cells, Fbxo2VHC specifically delineates otic progenitors and inner ear sensory epithelia. In mice, Venus expression and CreER activity reveal a cochlear developmental gradient, label the prosensory lineage, show enrichment in a subset of type I vestibular hair cells, and expose strong expression in adult cerebellar granule cells. We provide a toolbox of multiple spectrally distinct reporter combinations to the community for studies that require use of fluorescent reporters, hygromycin selection, and conditional Cre-mediated recombination.\n\nSUMMARY STATEMENTA multifunctional Fbxo2-targeted reporter in mice and stem cells was developed and characterized as a resource for inner ear studies, along with a toolbox of plasmids to facilitate the use of this technique for other users.