Fig. 5.

Cochlear and auditory projection development depends on the expression of specific genes. The development of spiral ganglion neurons (SGN; A’) depends on the expression of Neurog1. Their projection extends from the cochlea (A”, B) and ends in a topologically organized projection in the auditory nuclei (AVCN, PVCN, DCN) whose development depends on the expression of Atoh1 (A, B). Also shown are the vestibular ganglion neurons (VGN, A’), which project from the 5 vestibular sensory endorgans (anterior, posterior and horizontal semicircular canals, AC, PC, HC, and utricle and saccule, U, S; A”) to the central vestibular nuclei and cerebellum (CB; A). SGNs proliferate in a spatiotemporal gradient from the base to the apex of the cochlea during the embryonic period E10.5-E12.5 (B). Their central projections develop topologically from dorsal to ventral positions within the central auditory nuclei over approximately the same period (E10.5.E13.5; B). Later, hair cells proliferate in a gradient from the apex to the base of the cochlea during the period E12.5-E14.5 (B), and contact the peripheral terminals of the SGNs. AC, anterior crista; AVCN, anteroventral cochlear neurons; CB, cerebellum; aLL, pLL, anterior/posterior lateral line neurons; DCN, dorsal cochlear neurons; HC, horizontal crista; PC, posterior crista; r2/4/6, rhombomeres; S, saccule; SC, spinal cord; U, utricle. Modified from (Filova et al., 2022, Fritzsch et al., 2019, Macova et al., 2019, Nichols et al., 2008).