Figure 3. Immunoreactivity for Kir4.1 and MelEM as a function of age. A, B, With the exception of a low level of immunoreactivity in the abluminal side of the 3-week-old stria, Kir4.1 is not expressed in the tyr-DT-A (TG/TT) mice. C, D, MelEM, a protein specific to immature neural crest-derived melanoblasts, is present in high levels in the tyr-DT-A mouse at 3 weeks of age compared with the age-matched controls. E, F, Reactivity for Kir4.1 is noted at all ages in the C57 StV, with the most intense expression present at 7 weeks of age. G, H, MelEM continues to be present in high levels in the tyr-DT-A mouse at 7 weeks of age. I, J, No Kir4.1 reactivity is noted at 16 weeks of age. K, L, MelEM expression decreases in the C57 as a function of age. The expression is highest at 2 weeks of age (data not shown) and decreases to a low level by 7 weeks of age, with no expression of the protein at 16 weeks of age. Scale bar, 20 μm.