Effect of gene therapy on auditory brainstem responses and retina integrity. (A-B) ABRs were measured on gene therapy–treated (n = 9) and control mice (n = 9 for WT and 5 for MPS I) 6 months after treatment. (A) Representative response after auditory stimulation in WT, MPS I, and GT mice was measured as the following: for each mouse, 3 series of waves (obtained by an average of 500 electrical signals each) were recorded (shown in the top panel). In the bottom panel, the resultant wave obtained by the average of the 3 traces is shown. The latency of waves I and IV was measured as shown by the pink and green lines, respectively. (B) ABR scores of wave I (left chart) and wave IV (right chart) latencies are shown. (C-D) Retinal thickness (D) of MPS1, GT, and WT mice (n = 3) measured on ×20 magnification pictures upon DAPI (4,6 diamidino-2-phenylindole) staining, as shown in the representative images in (C). n = 3 mice analyzed per group (≥ 6 representative images per mouse). PE indicates photoreceptor layer; ONL, outer nuclear layer; INL, inner nuclear layer; and GCL, ganglion cell layer. The white bar in the picture on the left shows the measured thickness. Mean and SD are shown (*P < .05; **P < .01; ***P < .001 with 1-way ANOVA).