APP and Alzheimer disease: More recently, loss of function mutation in the dhtt gene was shown to enhance defects in axon outgrowth in the Mushroom body due to decreased function of the App gene, the Drosophila orthologue of the human amyloid beta-precursor protein (APP) gene, responsible of Alzheimer’s disease, suggesting an interaction between those genes that may control the onset of AD (Marquilly et al., 2021).