Figure 3. Ubiquitous Cre-mediated excision of the human AR121 transgene rescues systemic and neuromuscular phenotypes in BAC fxAR121 mice.

(A) We measured hAR transgene expression in 6 week-old male BAC fxAR121 – CMV-Cre bigenic mice in comparison to singly transgenic male BAC fxAR121 mice (n = 3 / group) by qRT-PCR analysis. We observed marked reductions in hAR transgene expression in the brain and quadriceps muscle of BAC fxAR121 – CMV-Cre bigenic mice. Results are normalized to hAR transgene expression in BAC fxAR121 brain, which was set to 1. ***P < .001, *P < .05, t-test.

(B) Western blot analysis of cortex and spinal cord for 6 week-old male BAC fxAR121 – CMV-Cre bigenic mice and littermate male BAC fxAR121 mice indicates that hAR protein expression is no longer detectable in BAC fxAR121 – CMV-Cre bigenic mice, when immunoblotted with human-specific anti-AR antibody. The first lane contains protein isolated from HEK293 cells transfected with a hAR125Q expression construct, and YAC AR100 protein lysates are included as an additional positive control. β-actin immunoblotting serves as a loading control.

(C) Ubiquitous Cre expression in BAC fxAR121 mice rescues weight loss in 16 week-old male BAC fxAR121 – CMV-Cre bigenic mice (n = 4 – 10 / group). **P < .01, ANOVA with post-hoc Tukey test.

(D) Ubiquitous Cre expression in BAC fxAR121 mice rescues grip strength in 13 week-old BAC fxAR121 – CMV-Cre bigenic mice (n = 4 / group). Grip strength is given in arbitrary units, with BAC fxAR121 performance set to 1. *P < .05, ANOVA with post-hoc Tukey test.

(E) Kaplan-Meier plot of male BAC fxAR121 mice and male BAC fxAR121 – CMV-Cre bigenic mice (n = 9 / group) reveals significantly extended lifespan in BAC fxAR121 – CMV-Cre mice. P < .0001, Log-rank test. BAC fxAR121 – CMV-Cre bigenic mice are still alive and well beyond 24 months of age. Error bars = s.e.m.