Age dependence of peak chloride conductance (G_ClC-1) and Clcn1 exon 7a inclusion. (A) G_ClC-1 of individual muscle fibers as a function of time. Linear regression lines are shown as solid black lines for WT and broken red lines for R6/2 fibers. There was a significant difference between WT and R6/2 slopes (P = 0.019), a significant increase in WT G_ClC-1 over time (P = 0.045), and no significant change in R6/2 G_ClC-1 over time (P = 0.174). (B) Mean G_ClC-1 per mouse with 95% confidence intervals for WT (black) and R6/2 (red) data points. The slope of the R6/2 regression line was −0.006 ± 0.004 G_ClC-1/day, and the slope of the WT regression line was 0.009 ± 0.004 G_ClC-1/day. (C) Age dependence of aberrantly spliced Clcn1 mRNA (with exon 7a) per mouse with 95% confidence intervals for WT (black) and R6/2 (red) data points. There was no significant change in R6/2 exon 7a+ overtime (P = 0.553), a significant decrease in WT exon 7a+ over time (P = 0.026), and a significant difference between R6/2 and WT slopes (P = 0.041). Note, two R6/2 Exon 7a+ data points overlap (32 d, 13.3%). The slope of the R6/2 regression line was 0.010 ± 0.017% exon 7a+/day and the slope of the WT regression line was −0.045 ± 0.019% exon 7a+/day.