Genetic modifiers of degeneration in the cathepsin D deficient Drosophila model for neuronal ceroid lipofuscinosis.

Neuronal ceroid lipofuscinoses (NCLs) are pediatric, neurodegenerative, lysosomal storage disorders. Mutations in cathepsin D result in the most severe, congenital form of NCLs. We have previously generated a cathepsin D deficient Drosophila model, which exhibits the key features of NCLs: progressive intracellular accumulation of autofluorescent storage material and modest neurodegeneration in the brain areas related to visual functions. Here we extend the phenotypic characterization of cathepsin D deficient Drosophila and report that modest degenerative changes are also present in their retinae. Furthermore, by utilizing this phenotype, we examined the possible effect of 17 candidate modifiers, selected based on the results from other cathepsin D deficiency models. We found enhancers of this phenotype that support the involvement of endocytosis-, lipid metabolism- and oxidation-related factors in the cathepsin D deficiency induced degeneration. Our results warrant further investigation of these mechanisms in the pathogenesis of cathepsin D deficiency.