Scanning electron microscopy (SEM)
The morphology of the stereocilia of cochlear hair cells was examined using SEM, as described previously(Guo et al., 2015). Briefly, cochlea samples from wild-type and heterozygous pigs at postnatal day 7 were fixed with 2.5% glutaraldehyde, decalcified in 10% EDTA, post-fixed in 1% OsO4, dehydrated in graded ethanol (50–100%), and dried in a critical point dryer (HCP-2, Hitachi) using liquid CO2. Then, fixed sections were coated using a sputter coater and examined under a Hitachi S-3700N scanning electron microscope (SEM, Japan) from the basal, middle, and apical areas of each cochlea.