SOD1 and amyotrophic lateral sclerosis: In addition, the reduction in the levels of VEGF in the SOD1 mutant mice by crossbreeding the SOD1 mouse model of ALS with VEGFδ/δ mice worsened the disease, resulting in a decrease in survival due to more severe motoneuron degeneration and earlier onset of muscle weakness (Lambrechts et al., 2003).