Labeling of inner ear afferents in the transgenic thy1 ‐YFP‐H mouse

We wished to assess the level of inner ear endorgan labeling in a transgenic mouse expressing yellow fluorescent protein (YFP) driven by the thy1 promoter and to examine the possibility of using this thy1 ‐YFP‐H mouse as a model for studying inner ear afferents. End‐organ YFP fluorescence in a postnatal day 8 (P8) thy1 ‐YFP‐H mouse was observed using confocal microscopy after anesthetizing the animal, then transcardially perfusing it with PBS and 4% paraformaldehyde. Images from utricular and cochlear whole mounts and crista sections suggest that in the thy1 ‐YFP‐H P8 mouse, vestibular afferents, including both calyces and boutons and type I and II spiral ganglion afferents are labeled. Afferents in the striolar region were more intensely labeled than extrastriolar afferents, and no supporting cell labeling was observed. Cochlear afferents, including those innervating both inner and outer hair cells, were also labeled. In conclusion, the thy1 ‐YFP‐H mouse could be a useful model in which to study inner ear endorgan structure and function as it lends itself to in‐vivo imaging and enables easy identification and distinction of afferent types and regions. Supported by NIH DC‐02521. Grant Funding Source NIH DC‐02521