The increased accumulation of aggregated TDP-43 on serial passage may suggest more efficient propagation on passage and raises the possibility of the existence of strains of pathological TDP-43; a phenomena first demonstrated in the prion diseases, but more recently also demonstrated with alpha synuclein (Bousset et al., 2013, Guo et al., 2013, Peelaerts et al., 2015) and Tau (Sanders et al., 2014). Here, MAPT is linked to prion disease.