This was confirmed in cases of mucopolysaccharidosis (MPS), whereby HS GAG accumulation in neurons lead to progressive aggregation of Aβ, tau, α-synuclein, and prion proteins in neurons in brains of young children with HS enzyme deficiencies (i.e., lack of sulfatases to degrade the accumulation of HS GAGs; Ginsberg et al., 1999; Reinhard et al., 2013; Beard et al., 2017; Bigger et al., 2018). Here, MAPT is linked to mucopolysaccharidosis.