MAPT and early-onset autosomal dominant Alzheimer disease: As hyperphosphorylated tau exists in these animals and is a hallmark pathological feature of Alzheimer's disease, understanding the progression from hyperphosphorylated tau to NFT formation and its implications on cognitive decline is critical to determine the full potential of these animals as research models for this disease.48 Chambers et al.64 suggest that cats develop NFT, but aged dogs do not, possibly due to the involvement of Aβ in furthering tau pathology, and vice versa.