: a new CRE driver to regulate gene expression in the otic placode lineage and other FGFR2b-dependent epithelia.

Pan-otic CRE drivers enable gene regulation throughout the otic placode lineage, comprising the inner ear epithelium and neurons. However, intersection of extra-otic gene-of-interest expression with the CRE lineage can compromise viability and impede auditory analyses. Furthermore, extant pan-otic CREs recombine in auditory and vestibular brain nuclei, making it difficult to ascribe resulting phenotypes solely to the inner ear. We have previously identified as an otic placode-specific target of the FGFR2b ligands FGF3 and FGF10. We show here that is otic specific through E10.5, but is not required for hearing. We targeted to the stop codon, generating mice, and observed CRE activity throughout the otic epithelium and neurons, with little activity evident in the brain. Notably, recombination was detected in many FGFR2b ligand-dependent epithelia. We generated and conditional mutants, and activated an FGFR2b ligand trap from E17.5 to P3. In contrast to analogous mice generated with other pan-otic CREs, these were viable. Auditory thresholds were elevated in mutants, and correlated with cochlear epithelial cell losses. Thus, provides a useful complement to existing pan-otic CRE drivers, particularly for postnatal analyses.