Mutanlallemand (mtl) and Belly Spot and Deafness (bsd) Are Two New Mutations of Lmx1a Causing Severe Cochlear and Vestibular Defects
Figure 5
Morphology of inner ears and analysis of sensory patches in mutants.
A–F, Paint-filled inner ears from mtl and bsd mutants at E16.5. Inner ears (front and back views) from wildtype (A, B), mtl/mtl (C, D) and bsd/bsd (E, F) mice are shown. Both homozygotes show under-developed cochlear ducts (red arrowheads) compared to their wildtype littermates. Vestibular system in homozygotes appears like a cyst without semicircular canals (white arrowheads). G, H, Confocal imaging and 3D reconstruction of P0 inner ears of one mtl mutant (G) and one wildtype (H). We used Myo7a (green) for sensory hair cells, rhodamine-phalloidin (red) for actin and DAPI (blue) for cell nuclei. The expression of Myo7a shows the main sensory patches in the inner ear (anterior, posterior and lateral cristae, utricle and saccule in vestibular system and organ of Corti in the cochlea) (H). In mtl mutants cristae can be identified by their relative position in the otocyst and utricle and saccule domains look abnormal compared to those in wildtypes (G, H). In mtl mutants there are two continuous Myo7a-positive hair cell populations descending to the truncated cochlea (insets). One of these populations show a quite uniform organization of the hair cells within the organ of Corti but without a tectorial membrane (I, area boxed in G), whereas the other population extending to a more distal location within the cochlea (K, L, area boxed in G) displays properties of a developing organ of Corti containing hair cells and a tectorial membrane (L). (K and L are reconstructions from the same confocal image stack. K, Organ of Corti surface, image sub-stack underneath tectorial membrane; L is a rotated and tilted 3D reconstruction of the same image stack). Asc, anterior semicircular canal; cd, cochlear duct; ed, endolymphatic duct; lsc, lateral semicircular canal; psc, posterior semicircular canal; sac, saccule, OHC, outer hair cells; IHC, inner hair cells; TM, tectorial membrane. Scale bars: A–F, 200 µm; G–H, 500 µm.