The expression of Hes6 is abolished in the absence of Math1. Adjacent cochlear sections from wild-type control (A–C) and Math1 null embryos (D–F) at E14.5 were probed for antisense probes against Math1 (A, D), Hes6 (B, E), or Islet1 (C, F). Arrows (A–B) indicate the columns of cells expressing Math1 (A) or Hes6 (B). Brackets (C, F) indicate the primordial organ of Corti. SG: spiral ganglion. Scale bar: 50 μm.