ABSTRACT Frontotemporal dementia (FTD) is a progressive neurodegenerative disease associated with focal atrophy of the prefrontal and/or temporal lobes. FTD is the second most common form of dementia among people under the age of 65. Many FTD-causing genes have been identified during the last decade, including CHMP2B, GRN, C9ORF72, and TBK1. Some of these genes are also implicated in the motor neuron disease amyotrophic lateral sclerosis (ALS), paving the way for in-depth mechanistic investigation of pathogenic processes in both disorders. In order to reveal common pathogenic mechanisms in different forms of FTD, it is critically important to investigate both common and rare genetic mutations. To this end, in this application, we will focus on the effects of FTD-causing mutations in CHMP2B and TBK1 on the functions of the endosomal- lysosomal and autophagy pathways, two closely linked cellular pathways for degradation of transmembrane and intracellular cargos. We will take advantage of strengths of different experimental systems including fruitfly Drosophila, mouse models of FTD and cortical neurons differentiated from CRISPR-engineered induced pluripotent stem cells (iPSCs). This multidisciplinary approach will greatly enhance our understanding of pathogenic mechanisms of FTD and reveal novel targets for therapeutic intervention.