Transgenic animals initially exhibit hindlimb weakness that spreads with rapid progression to forelimbs and results in muscle atrophy and complete paralysis within 2 weeks. Founders 148-G85R and 74-G85R are the highest and lowest expressing transgenic lines, respectively, and differ in onset of clinical symptoms, presumably due to gene dosage. Founder 148-G85R exhibits muscle weakness at 8-10 months of age whereas founder 74-G85R exhibits the phenotype 12-14 months of age. Despite the difference in disease onset both founders show the same rate of disease progression after appearance of initial symptoms.