Fig. 1. Graded increase in hair cell formation with a reduction in Notch ligand gene dosage. (A-D) Lectin-stained cochleae with only single null or hypomorphic mutations in the Dll1 or Jag2 genes show relatively normal hair cell numbers and patterning, although occasional extra inner or outer hair cells are observed (arrows). (E-H) Double heterozygous Dll1^+/- Jag2^+/- cochleae (E) demonstrate a similar increase in outer hair cells but not as large an increase in inner hair cells as Jag2^-/- cochleae (F). Dll1^+/- Jag2^-/- (G) or Dll1^hyp/-Jag2^-/- (H) cochleae show a large increase in hair cell formation when compared with Jag2^-/- cochleae (F). The hair cells in these cochleae are extremely disorganized. Scale bar: 50 µm.