A human MAPT cDNA encoding the longest tau isoform of 441 amino acids containing four repeats, with 2 N-terminal inserts, and also carrying an engineered mutation to alter codon 301 from one encoding proline to encoding leucine, was inserted into a murine Thy1 expression vector. Expression of the mutant human tau (MAPT*P301L) protein was detected in layers II, V and VI of the neocortex, in layer III of the entorhinal cortex, in thd basolateral amygdala, hippocampus, zona incerta of the thalamus, brain stem nuclei and spinal cord.