VPS33A and mucopolysaccharidosis-plus syndrome: ,14,15,16 To investigate the effect of the VPS33A mutation on cellular function in the same genetic background, we established VPS33A knock-out (KO), VPS33Ap.R498W heterozygous, and homozygous knock-in (KI) HeLa cells by the CRISPR/Cas9 method as a cellular model of MPSPS (Figure S1A).