Fig. 2. Paint-filled inner ears of Gbx2 mutants. Lateral views of right inner ears from heterozygous and homozygous Gbx2 embryos at 15.5 (A) and 11.5 dpc (B-E). (A) The control inner ear is shown on the left followed by four representative phenotypes, shown with increasing severity from Type I to IV. Type I: an enlarged membranous labyrinth lacking the endolymphatic duct (ed). Type II: absence of both the endolymphatic duct and common crus (cc, asterisk). The utricle (u) and saccule (s) are not easily discernible, and the cochlear duct is shortened. Type III: the inner ear is missing the anterior and posterior canals, in addition to phenotypes described for Type II. Type IV: a cystic inner ear with only the lateral canal and ampulla. (B) A normal inner ear at 11.5 dpc. (C-E) Gbx2 mutant ears with a normal (C), smaller (D) or non-existent (E) vertical canal pouch. asc, anterior semicircular canal; cc, common crus; cd, cochlear duct; ed, endolymphatic duct; es, endolymphatic sac; hp, horizontal canal pouch; lsc, lateral semicircular canal; psc, posterior semicircular canal; s, saccule; u, utricle; vp, vertical canal pouch. Scale bar in E applies to B-E.