Fig. 7. p27^Kip1 expression is drastically reduced in the Jag1 but not the Delta1 conditional knockout cochlea. Confocal optical sections of whole-mount E14.5 cochleas stained with anti-p27^Kip1 antibody and fluorescent phalloidin. The bright staining (asterisks) in tissue outside the sensory epithelium in the apex of the cochlea is non-specific and occurs in an area damaged during dissection. (A) Wild-type control. p27^Kip1 is expressed in a band of cells (arrow) corresponding to the future organ of Corti. (B) Delta1 conditional knockout littermate. There is little change in the expression of p27^Kip1 in the developing sensory patch, except that it extends further towards the apex in accordance with the premature differentiation of this region. (C) Wild-type littermate control for the Jag1 conditional knockout. (D) Jag1 conditional knockout, showing complete loss of expression of p27^Kip1 in the developing sensory patch (arrows in C,D). (E) Another Jag1 conditional knockout specimen, showing some weak residual expression of p27^Kip1 (arrow).