Here, we report the electron cryo‐microscopy structures of tau filaments from  undifferentiated seeded SH‐SY5Y cells that transiently expressed N‐terminally HA‐tagged 1N3R or 1N4R human tau, using brain extracts from individuals with Alzheimer's disease or corticobasal degeneration. This evidence concerns the gene MAPT and early-onset autosomal dominant Alzheimer disease.