Illustration of GER region used for measurement of area and cell number in non-Tg (A) and R75W + (B) mice at P12. Apical turn in the cochlear were observed using microscopy. The dotted line indicates the area of the GER, and the red line indicates the 50-μm-long region in which cells were counted. IPC, inner pillar cell; OPC, outer pillar cell; IHC, inner hair cell; OHC, outer hair cell; TC, tunnel of Corti. Scale bars = 50 μm.