Defining modifiers and mechanisms of RAN translation

Project Summary/Abstract Defects in protein translation are central to multiple neurodegenerative diseases, including Alzheimer’s disease and related dementias (e.g., frontotemporal lobar dementia). An unconventional form of translation has been shown to play a role in several neurodegenerative diseases associated with nucleotide repeat diseases. In these diseases, expanded nucleotide repeats get translated in an AUG-independent manner to produce aberrant peptides that may contribute to neurodegeneration. The mechanism of this unusual form of translation, called RAN translation, has remained poorly understood. The Gitler and Puglisi laboratories have joined forces to combine biophysics and genetics approaches to elucidate the mechanism of RAN translation. We developed new single-molecule methodologies to study translation dynamics in humans and combined these with biochemical and in vivo approaches to reveal a global mechanism for RAN translation and identified potent modifiers of RAN translation, at least one of which could mitigate degeneration in several frontotemporal dementia and amyotrophic lateral sclerosis (ALS) disease models. We propose new studies to gain even deeper understanding of RAN translation. We will also expand and extend our efforts to investigate a new facet of frontotemporal dementia (FTD) pathology that we recently discovered – altered processing of the 3’ end of certain mRNAs, which are targets of the FTD and ALS disease protein TDP-43. These altered 3’ ends of the mRNAs has profound effects on the translation of the mRNAs and we have evidence that at least one of them is directly linked to FTD. Our results will build on the foundation of the prior funding period and establish a coherent dynamic mechanism of RAN translation and its regulation from initiation through protein production. We will also illuminate a new facet of TDP-43 pathology in FTD and ALS and how this impacts protein translation. More broadly, our results will provide a mechanistic foundation for understanding the interplay of translation dynamics and fidelity and protein quality control in aging and neurodegenerative diseases, including dementia.