Figure 6.

Direct gene transfer demonstrates N-box–mediated utrophin-A promoter repression by ERF in vivo. Utrophin promoter-A constructs (wild type; with N-box) were coinjected with CAT (to monitor transduction efficiency) into TA muscles of 4-wk-old control mice with control (pSG5 vector) or ERF (pSG5-ERF) expression plasmid. A different cohort was injected using the mutant utrophin promoter constructs (ΔN-box; without N-box). Five days later, muscles were harvested, and then RNA extracted and qPCR analysis was performed. Values obtained for LacZ or luciferase are standardized relative to the amount of CAT present in the same sample, with the ERF-injected samples compared with their respective control (normalized to 100%). Student's t tests were used to analyze the data. The asterisk denotes the statistically significant (p < 0.02) decrease in promoter-A activation (∼30%) observed with the ERF plasmid (black bar) versus the control injected plasmid (white bar). No significant differences were observed using the ΔN-box construct. Error bars represent SEM; sample size for wild type, n = 5; ΔN-box, n = 10 for both ERF and control experiments.