COL4A2 and Leukoencephalopathy: Several genome-wide association studies (GWAS) have identified single-nucleotide polymorphisms (SNPs) in the following genes: TRIO, PRKG1, ANK1, COL4A2, NTN1, and ASTN2 that were associated with increased risk of MTX-induced neurotoxicity and leukoencephalopathy on imaging in patients with ALL.