Mutations in SCN4A and Scn4a and functional characterization. (A) Family history of the c.1762A>G; I588V mutation. Proband indicated by arrow, affected family members are shaded. Females represented by circles and males by quadrangles. (B) Sequence trace showing the Scn4a c.1744A>G; p.I582V mutation in draggen mice. (C) Voltage dependence of activation (circles), fast inactivation (squares) and slow inactivation (triangles) for human (h) wild-type (black) and I588V (red) hNa_v1.4 channels. The y-axis shows normalized conductance (activation) or current (fast and slow inactivation). The lines through the data are the best fit of the Boltzmann equation to the data. Data and statistical analysis are represented in Table 1.