To begin to examine which cell types in the CNS may participate in the propagation of SOD1 ALS conformers, we developed a line of G85R-SOD1:YFP mice in which the transgene construct had been modified to encode loxp recombination sites that would delete coding sequences when exposed to Cre recombinase (Figure 4A). The gene discussed is SOD1; the disease is amyotrophic lateral sclerosis.