FOLH1 and Canavan disease: Despite the white matter diseaseslinked to NAAGlevels like Pelizaeus–Merzbacher disease, Pelizaeus–Merzbacher-likedisease, and Canavan disease,28−30 a detrimental phenotype was notobserved in GCPII-deficient mice;24 therefore,the high concentration of NAAG is likely the side effect and not thecause.