The strength of AV-1451 binding with respect to tau isoforms that preferential accumulate in various neurodegenerative disorders was as follows: 3R + 4R tau (e.g., AD) > 3R tau (e.g., Pick disease) or 4R tau and also matches the pattern seen by Sander et al. Our findings suggest that disorders with tau pathology have sufficient differences with respect to binding to PET ligands that they may need to be tailored to particular tau species. The gene discussed is MAPT; the disease is Alzheimer disease.