SDC4 and Alzheimer disease: In addition, increased SDC3 and SDC4 expression has been found in post-mortem human AD brains (Grothe et al. 2018; Hudák et al. 2021) and SDC2 and GPC1 to act as Aβ receptors (Jarosz-Griffiths et al. 2016; Letoha et al. 2019; Reinhard et al. 2013).