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. Author manuscript; available in PMC: 2014 Feb 10.
Published in final edited form as: Dev Cell. 2003 Jul;5(1):45–57. doi: 10.1016/s1534-5807(03)00169-2

Figure 3. Sema–Npn-1 Signaling Is Required for Sensory Afferent Innervation of the Inner Ear and Spinal Cord.

Figure 3

(A–C) In E12.5 npn-1Sema− mice, vestibular nerve fibers extend beyond the anterior and horizontal cristae (AC, HC) and reach the skin above the ear ([B], top arrow). In addition, fiber bundles extend from the utricle (U) to the posterior crista (PC) where they may leave the ear through the round window ([B], bottom arrow; data not shown). In some animals, vestibular fibers are observed projecting around the forming cochlea without innervating any target ([C], arrow).

(D–G) E15.5 npn-1Sema−mutants form inner ear afferent fibers to the skin. These fibers extend beyond the anterior cristae (E), pass through the otic capsule, and run together with the auriculotemporal nerve to the skin anterior to the auricle (arrow). Injection of dye into this area of the skin labels nVIII fibers that pass through the lateral otic wall (F) and pass underneath the canal cristae where some fibers branch and provide afferents to those epithelia (arrow). These fibers come from vestibular ganglion neurons (G) which project centrally into vestibular nuclei (data not shown).

(H–K) Abnormal central projections of spinal sensory afferents. TrkA immunohistochemistry of E14 (H and I) and P2 (J and K) lumbar spinal cord in npn-1Sema− (I and K) and wild-type littermates (H and J), examined by confocal microscopy. Dorsal spinal cord is at the top. Scale bars: (A–G), 100 μm; (H–K), scale bar in (G) is equal to 200 μm in (H)–(K).