We previously developed a panel of single chain antibody variable domain (scFv) based reagents that very selectively bind toxic disease-related variants of tau, Aβ, TDP-43, and α-syn that are present in post-mortem validated human neurodegenerative disease brain tissue, but not in cognitively normal, age-matched human samples [28–33]. This evidence concerns the gene MAPT and neurodegenerative disease.