Hyperphosphorylated tau aggregates in the cortex and hippocampus of transgenic mice with mutant human FTDP-17 Tau and lacking the PARK2 gene.

Mutations in the PARK2 gene encoding parkin cause autosomal recessive juvenile parkinsonism, but have also been found in patients diagnosed with certain tauopathies. Conversely, mutations in the MAPT gene encoding tau are present in some types of parkinsonism. In order to investigate the possible relationship between these two proteins, we generated a double mutant mouse that is deficient in PARK2 and that over-expresses the hTauVLW transgene, a mutant form of the tau protein present in FTDP-17. Independent deletion of PARK2 or over-expression of the hTauVLW transgene produces mild phenotypic alterations, while a substantial increase in parkin expression is observed in hTauVLW transgenic mice. However, double mutant mice present memory and exploratory deficits, and accumulation of PHF-1 and AT8 hyperphosphorylated tau epitopes in neurons. These phenomena are coupled with reactive astrocytosis, DNA fragmentation, and variable cerebral atrophy. Here, we show that cortical and hippocampal neurons of double mutant mice develop argyrophilic Gallyas-Braak aggregates of phosphorylated tau from 3 months of age. Their number decreases in old animals. Moreover, numerous phosphorylated tau aggregates were identified with the conformation-dependent Alz-50 antibody and the S-Thioflavin staining. Ventral motor nuclei of the spinal cord also present Alz-50, AT8, and PHF1 hyperphosphorylated tau aggregates when parkin is deleted in mice over-expressing the hTauVLW transgene, begining at early ages. Thus, the combination of PARK2 gene deletion with hTauVLW over-expression in mice produces abnormal hyperphosphorylated tau aggregates, similar to those observed in the brain of patients diagnosed with certain tauopathies. In the light of these changes, these mice may help to understand the molecular processes responsible for these diseases, and they may aid the development of new therapeutic strategies to treat neurodegenerative diseases related to tau and parkin proteins.