Conserved effect of dominant negative SCA13 mutation inserted into zebrafish Kv3.3. A) R335H RNA did not generate functional channels when injected alone into oocytes. The membrane was pulsed from a holding potential of -90 mV to voltages ranging from -80 to +60 mV in 10 mV increments. B) RNA for wild type zebrafish Kv3.3 (0.1 ng) and the R335H mutant were mixed in the indicated ratios and injected into oocytes. Representative current traces obtained from each mixture at +40 mV have been superimposed. C) The fraction of wild type current amplitude remaining has been plotted versus the injected ratio of wild type:R335H RNA. Amplitudes were measured at +40 mV. Means differed significantly by one way ANOVA (p < 0.0001) followed by Student's t-test, (1:0, n = 13; 1:0.5, n = 18; 1:1, n = 13; 1:2, n = 15; 0:1, n = 7). Pairwise comparisons: ***, significantly different from wild type alone (1:0), p < 0.001; **, significantly different from 1:1 ratio, p < 0.005.