Figure 4.

Prosaposin expression in the null mutant (knock-out) mouse. Prosaposin antibody labeling demonstrates the absence of prosaposin in the KO mouse organ of Corti. A, B, Compared with WT mice (A), homozygote prosaposin KO mice lack prosaposin expression within the organ of Corti (B). TC, Tunnel of Corti. C, In the homozygous (KO) mice, Western blot analysis demonstrates a lack of prosaposin expression within the brain, a known location of prosaposin, in contrast to heterozygote and WT mice (black arrow). In all three brain lanes, there is nonspecific banding (red arrows); because the band also appears in the KO sample, it is not prosaposin labeling. The nonspecific band does not appear in the cochlear samples, and, thus, the labeling seen in the cochlea likely represents true prosaposin labeling. The brain serves as a positive control whereas the liver serves as a negative control in each experiment.