RNA localization and local protein synthesis enable highly differentiated, post-mitotic cells, such as neurons, to respond to external perturbations and adjust protein levels in specialized compartments in a timely and efficient manner. Proper RNA localization and local translation are necessary for neuronal functions that underlie learning and memory. Myotonic Dystrophy Type 1 (DM1), which affects 1 in 8000 worldwide, is an example of disease in which RNA mislocalization may contribute to disease progression. While the muscular symptoms of DM1 have been thoroughly studied, DM1 patients also present with multiple debilitating CNS symptoms, such as hypersomnia, anhedonia, and neurocognitive/behavioral disorders. It is critical to elucidate the basic mechanism of RNA localization in healthy neurons to better understand the CNS symptoms associated with a disease involving RNA mislocalization, such as DM1. In this proposed project, we plan to utilize a multi-faceted approach that combines multiple imaging and biochemical techniques. Primary cortical neurons from wild type mouse embryonic brains will serve as our principal model. The Bassell Lab has extensive background in studying RNA biology and has published extensively on the roles of the RNA-Binding Proteins (RBPs) Fragile X Mental Retardation (FMRP) and Survival of Motor Neuron (SMN) proteins which are also affected in related neurological diseases. The goal of this project is to elucidate the role that a specific RBP implicated in DM1 pathogenesis, Muscleblind (MBNL), has as a facilitator of mRNA localization from the cell body to pre-synaptic compartments. We hypothesize that MBNL acts an adaptor between its mRNA cargo and specific kinesin motor proteins (Kifs). Kinesin was chosen over other motor proteins as the focus of this proposal because it is well-established that kinesins facilitate the long distance anterograde movement of the cellular cargo away from the soma. Another goal of this project is to identify the specific Kifs that interact with MBNL to transport target mRNA transcripts to proper destinations within neurons. Depending on the cargo and destination, certain Kifs or combinations of Kifs might necessary for proper transportation. This work will strengthen our understanding of RNA localization and the role that RBPs play in this process. This research will also motivate future studies to identify various components of RNA transport granules, necessary not only for localization, but also granule formation, anchoring, and disassembly. The knowledge gained from this project could be applied to pathological conditions that arise due to RNA mislocalization, such as DM1.
The proposed basic research is focused on better understanding molecular mechanisms of how mRNAs are localized in neurons to affect protein levels important for synapse function during brain development. This research has direct implications for understanding CNS symptoms in Myotonic Dystrophy, but also other neurological diseases with perturbations to these fundamental processes.
