GPC4 and early-onset autosomal dominant Alzheimer disease: To investigate whether microglia express GPC4 in neurodegeneration, we performed immunohistochemistry on human brain sections containing Aβ plaques and neurofibrillary tangles (Alzheimer’s disease), neurofibrillary tangles only (corticobasal degeneration), Aβ plaques only, or neither (healthy age-matched control tissue) (Supplementary Material 14).