MAPT and tauopathy: Tau-mediated degeneration of photoreceptor neurons in the Drosophila visual system is a commonly used in vivo model to study the cell biology of the tauopathies (Wittmann et al., 2001; Jackson et al., 2002; Muqit and Feany, 2002; Nishimura et al., 2004; Karsten et al., 2006; Steinhilb et al., 2007a; Khurana, 2008; Chatterjee et al., 2009).