YAP1 and neoplasm: Although wts null mutants show some loss of neuronal differentiation and impairment of polarity (Menut et al. 2007) tumor formation solely due to elevated Yki activity has not been observed previously in Drosophila. It is worth noting that overexpression of YAP has been shown to lead to neoplasia in mouse liver and intestinal epithelial models (Dong et al. 2007; Cai et al. 2010).