SDC1 and Alzheimer disease: Other HSPGs later found to be present in amyloid and neuritic plaques and elevated in AD brain (Liu et al., 2016) besides perlecan included the HSPGs agrin, glypican-1, glypican-3, and syndecans 1–4 (Verbeek et al., 1999; Watanabe et al., 2004; Liu et al., 2016; Lorenta-Gea et al., 2020).