Misfolded, hyperphosphorylated tau is the major constituent of neurofibrillary tangles in Alzheimer disease, as well as the inclusions in Pick disease and progressive supranuclear palsy. Twenty different mutations in the tau gene cause neurodegeneration in fronto-temporal dementia Parkinsonism-17, some influencing splice ratios and others changing tau's sequence. We postulate that alterations in tau conformation are a common underlyiing theme in these disorders. We propose to develop new technologies to tackle the question of tau conformation and tau expression at the cellular level, using neuropathological material from the ADRC brain bank and from colleagues across the country. In the first aim, we will develop novel fluorescence resonance energy transfer (FRET) techniques using fluorescence lifetime imaging to monitor the proximity of different domains of the tau protein in neurofibrillary tangles. Already we have found a unique folded structure in which the N terminus is folded back upon the microtubule binding domain region, while the C terminus is in close proximity to the proline rich domain.
The second aim utilzes laser capture microdissection methods to identify and select individual neurons with (or without) neurofibrillary tangles for protein and mRNA analyses. The latter will be carried out using quantitaitve PCR approaches as well as a new method (called polony exon typing) that determines all 6 tau isoforms from microscale amounts of mRNA.
In aim 3, the results obtained from the study of neurofibrillary tangles in Alzheimer disease will be compared to parallel studies of non-Alzheimer tauopathies: sporadic Pick disease, progressive supranuclear palsy, and cases of FTDP-17 with known tau mutations. Development of these novel methods will allow for examination of protein structure, expression, and mRNA patterns with a cellular level of resolution. These novel technologies will not only address important questons about tau's role in neurodegenration, but also provide a platform for further investigations of protein and mRNA in Alzheiemr and related dementias. Furthermore, the proposed program integrates closely with the core resuorces of the ADRC and with the other scientific projects within the ADRC, as well as other ADRCs and scientific centers of excellence across the country and in Europe.
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