P1-095: CNS stem cell lines from tau transgenic mice as models for frontotemporal dementia

Human stem cell lines that capture the genetics of disease susceptibility provide new research tools. To assess the utility of stem cells to study neurodegenerative disease we are using mouse central nervous system stem cell-containing neurosphere cultures. We previously have used this system to study aspects of prion disease in vitro and are now investigating the utility of neurospheres to model tauopathies, which, like prion diseases, arise from protein misprocessing events. Tauopathies are characterized by hyperphosphorylation, aggregation, and neurofibrillary tangle formation of the microtubule associated protein tau. Transgenic mice expressing a mutant human tauP301L transgene under the control of a tetracycline responsive element are crossed to transgenic mice that express the tetracycline transactivator under control of the calcium calmodulin kinase promoter. The resulting rTg(tauP301L)4510 (rTg4510) mice display cellular, histological, biochemical and behavioral phenotypes similar to frontotemporal dementia in humans. Neurosphere cultures derived from rTg4510 mice will be compared to cultures derived from similar mice that express the human wild type tau transgene, rTg(tauwt)21221 (rTg21221). We have generated neurosphere lines from embryonic day 14 rTg4510, rTg21221, and non-expressing mice. Human tau expression is detected by Western blot and immunofluorescence in tauP301L and tauwt cell cultures but not in controls. Human tau expression is maintained over several passages in both undifferentiated neurospheres and differentiated cells derived from them. Human tau expression does not alter cell growth rates regardless of human tau genotype. However, tauP301L transgene expression may affect cell types in the culture following differentiation stimuli. Using immunofluorescence, both glial and neuronal markers are observed post-differentiation in all genotypes. The proportion of cells co-expressing neuron-specific antigens and human tau is higher in tauwt expressing cultures than in tauP301L expressing cultures. The number of cells co-expressing glial antigens and human tau transgene, however, are similar among culture genotypes. We are now investigating tau pathology in cultured neurospheres using tau hyperphosphorylation and aggregation as surrogates for disease progression in vitro. Our results suggest that tauP301L expression affects neurosphere cultures differently from tauwt expression and that stem cell cultures may be useful models for neurodegenerative diseases.