Studies conducted in a transgenic mouse model of tauopathy expressing the familial FTD-related P301L form of mutated tau in oligodendrocytes demonstrated early loss of axonal transport and significant myelin loss in the spinal cord, which was followed by generation of Thio S-positive aggregated tau and axonal degeneration, resulting in muscle atrophy and motor impairments. The gene discussed is MAPT; the disease is frontotemporal dementia.