In this study, we use selective and ultrasensitive diagnostic biomarker assays, known as real-time quaking-induced conversion (RT-QuIC) assays to directly and selectively measure AD (i.e. 3R/4R) tau seeds [31, 43] in AD and Lewy body disease (LBD) cases, as well as those representing different stages of AD pathology. This evidence concerns the gene MAPT and Alzheimer disease.