An AA to GC change resulting in a lysine to alanine substitution at amino acid 80 (p.K80A) was introduced in exon 3. In addition, a loxP site was inserted upstream of exon 3 and an FRT-flanked neomycin resistance cassette and second loxP site were inserted downstream of exon 3. The neomycin resistance cassette was removed via flp-mediated recombination. The p.K80A missense changes abolishes its GPTase activity. qPCR indicates that mRNA levels are similar to wild-type levels, however mutant protein levels in the brain and spinal cord are moderately lower.