Fig. 1. Embryonic development of the cochlear epithelium. Isolated epithelial wholemounts from E12.5 to E17.5 embryos, which carry an EGFP transgene (green) under the control of a Math1 enhancer. EGFP expression (green) marks the sites of the developing sensory regions in the inner ear. (A) The entire E12.5 otic epithelium is shown. Math1/EGFP is expressed in the vestibular sensory primordia, utriclus (ut), sacculus (sa) and three cristae (cr), but not in the nascent cochlear duct (co). en, endolymphatic sac. (B-D) Math1/EGFP expression begins in the mid-basal region of the cochlear duct sometime between E13.5 (B) and E14.5 (C). From this region, expression of Math1/EGFP progresses in a gradient that spreads longitudinally towards both the hook region at the extreme base of the cochlea and the apical tip of the cochlear duct, as well as from medial to lateral across the developing organ of Corti. The process of patterning the cochlea is complete between E17.5 (D) and E18.5. Scale bar: 200 µm.
