Statistical analyses
For qRT-PCR data, values are expressed as ratios (to uninjected eye) of mean relative expression (±S.E.M.). Since ratios have an inherently skewed (non-Gaussian) distribution, data were log-transformed before undergoing one-way ANOVA. For ERG data, nanoparticle-injected groups were compared with naked DNA-injected groups. All groups passed the Kolmogorov-Smirnov test for normality and P-values are from two-tailed, unpaired Student's t-tests. In cases where unequal variance was found (per an F-test), Welch's correction was applied (http://web.uccs.edu/lbecker/SPSS/ttest.htm). Means and standard errors are reported in Table 1 as indicated. To determine whether there was any significant change in ERG amplitude over time, two-way ANOVA with Bonferroni's post-hoc test was used to compare treatment groups at different ages. To determine whether naked DNA caused any effect on function, one-way ANOVA with Bonferroni's post-hoc test was used to compare CBA-NMP naked DNA, IRBP-NMP naked DNA, and saline injected groups.