N-myc expression in the embryonic cochlea of the mouse

N-myc expression in the mouse embryo was examined during the late cochlear organogenesis. Tissue distribution of N-myc expression was histologically analyzed by in situ hybridization of the transcript in the cochlea between 15 and 18 days of gestation. At 15 days of gestation, N-myc expression was found very conspicuous in nervous structure of the cochlea such as the auditory nerve and the spiral ganglion. Moreover, N-myc was also present in the Köllikers organ and in the epithelium surrounding the cochlear canal. A few days later, N-myc expression was still clearly present in the Köllikers organ but less so in nervous structures. This study shows that cochlear tissues derived from the otic placode present a significant level of N-myc transcript during late embryogenesis. N-myc expression seems to be related to cell differentiation in the inner ear.