Antisense Oligonucleotides for Targeting Nonsense-mediated mRNA Decay in Frontotemporal Dementia

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Project Summary Progranulin is a lysosomal and secreted protein that contains multiple cysteine-rich granulin domains; its precise molecular function remains unknown. Progranulin (GRN) mutations are causal for frontotemporal dementia (FTD), which is a devastating disease with a mean survival of 3.8 years from diagnosis and no cure currently available. Since progranulin-deficient FTD is a disease of haploinsufficiency, strategies aimed at increasing progranulin levels are feasible therapeutic approaches. We recently generated a knock-in mouse model of FTD harboring the common patient nonsense mutation GRNR493X, and we established that the nonsense-mediated mRNA decay (NMD) pathway contributes to the markedly reduced mutant progranulin mRNA levels in this mouse model, as wel`l as in patient-derived fibroblasts containing the GRNR493X mutation. Moreover, our cell-based studies indicate that the progranulin R493X mutant protein is functional when re- expressed in progranulin-deficient cells. Based on these results, we hypothesize that inhibiting NMD-mediated degradation of the mutant GrnR493X mRNA would increase functional progranulin levels and thereby improve FTD-associated behavioral changes and neuropathology. We will test this hypothesis in the following two specific aims: Aim 1) Test in vivo efficacy of ASOs that block NMD-mediated degradation in the GrnR493X knock-in mouse model of FTD, and Aim 2) Design and test ASOs that target NMD-mediated degradation of the human GRNR493X mRNA. Completion of these studies will generate important preclinical data that provide insights into the utility of ASO-based NMD inhibition as a therapeutic approach for progranulin-deficient FTD.