Investigating the role of NMD in Nonsense Mutation Biology and Therapeutic Strategies

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There is a great need for treatments for diseases caused by nonsense mutations. In the context of Cystic Fibrosis (CF), caused by mutations in the CFTR gene, patients with two nonsense alleles lack CFTR-specific treatments. CF provides a useful context in which to study nonsense mutation biology as CF is a well characterized genetic disease, has numerous model systems, and has dozens of nonsense mutations within CFTR. Nonsense-mediated decay (NMD) is the cellular process that degrades transcripts containing premature termination codons caused by nonsense mutations. NMD acts as a treatment barrier in nonsense mutation conditions by preventing protein from being translated as few nonsense transcripts remain in the cell. NMD, however, does not affect all nonsense transcripts equally. NMD efficiency has been suggested to vary by tissue, cell type, and even by patient. Furthermore, nonsense mutations in specific locations within the transcript escape NMD. This proposal aims to study the heterogeneity of NMD in CF nonsense mutations and the pharmacological correction of CF nonsense mutations. Novel mouse models containing CF nonsense mutations predicted to escape NMD will be developed. Using these NMD resistant models, NMD efficiency will be measured and compared to existing CF models containing NMD susceptible nonsense mutations. Using existing and new CF nonsense mouse models, pharmacological correction of nonsense mutations will be studied. NMD inhibitors will be investigated, as well as readthrough agents (capable of triggering the readthrough of premature stop codons), and CFTR modulators (which promote CFTR protein folding and function) will be tested independently and in combination in mouse and human intestinal organoids and ultimately in vivo in nonsense mutation mouse models. The best pharmacological combination may differ for each genotype or by NMD phenotype. Studying the role of NMD in CF heterogeneity and CF nonsense mutation correction may elucidate better therapeutic strategies and provide evidence for pursuing a precision medicine approach in CF. The training plan outlined in this proposal will strongly support a successful transition to a career in translational research for the trainee. The training plan includes activities relating to science communication, clinical and translational research, preclinical in vivo animal techniques, and bioinformatics.