Neurofibrillary tangles composed of hyperphosphorylated fibrillized tau are 
found in numerous tauopathies including Alzheimer's disease. Increasing evidence 
suggests that tau pathology can be transmitted from cell-to-cell; however the 
mechanisms involved in the initiation of tau fibrillization and spreading of 
disease linked to progression of tau pathology are poorly understood. We show 
here that intracerebral injections of preformed synthetic tau fibrils into the 
hippocampus or frontal cortex of young tau transgenic mice expressing mutant 
human P301L tau induces tau hyperphosphorylation and aggregation around the site 
of injection, as well as a time-dependent propagation of tau pathology to 
interconnected brain areas distant from the injection site. Furthermore, we show 
that the tau pathology as a consequence of injection of tau preformed fibrils 
into the hippocampus induces selective loss of CA1 neurons. Together, our data 
confirm previous studies on the seeded induction and the spreading of tau 
pathology in a different tau transgenic mouse model and reveals neuronal loss 
associated with seeded tau pathology in tau transgenic mouse brain. These 
results further validate the utility of the tau seeding model in studying 
disease transmission, and provide a more complete in vivo tauopathy model with 
associated neurodegeneration which can be used to investigate the mechanisms 
involved in tau aggregation and spreading, as well as aid in the search for 
disease modifying treatments for Alzheimer's disease and related tauopathies.