Elevated 4R-tau in Astrocytes From Asymptomatic Carriers of the MAPT 10+16 Mutation

The MAPT 10+16 intronic mutation causes frontotemporal lobar degeneration (FTLD) by increasing expression of four-repeat (4R)-tau isoforms. We investigated the potential role for astrocytes in the pathogenesis of FTLD by studying the expression of 4R-tau. We derived astrocytes and neurons from induced pluripotent stem cells from two asymptomatic 10+16 carriers and, compared to controls, showed persistently increased 4R:3R-tau transcript and protein ratios in both cell types. However, beyond 300 days culture, 10+16 neurons showed less marked increase of this 4R:3R-tau transcript ratio compared to astrocytes. Interestingly, throughout maturation, both 10+16 carriers consistently displayed different 4R:3R-tau ratios at transcript and protein levels. Our study shows elevated levels of 4R-tau in astrocytes implicating glial cells in the pathogenic process and also suggests a cell-type-specific regulation and may inform and help on treatment of preclinical tauopathies.