Previous studies have identified Apolipoprotein E (APOE), Cathepsin D (CTSD), and Brain-Derived Neurotrophic Factor (BDNF) as key players of neurodegenerative pathways with their variants associated with different neurodegenerative diseases.
The yeast Saccharomyces cerevisiae PEP4 gene encodes vacuolar endopeptidase proteinase A (Pep4p), which is a homolog of the human CTSD gene that encodes cathepsin D. Mutation of CTSD gene in human resulted in a number of neurodegenerative diseases.
Animal models of cathepsin D (CD) deficiency are characterized by a progressive and relentless neurodegenerative phenotype similar to that observed in Neuronal Ceroid Lipofuscinoses (NCL), a group of pediatric neurodegenerative diseases known collectively as Batten Disease.