TDP43 mRNA complex transport in physiologic and pathologic states



 DESCRIPTION (provided by applicant): This proposal describes a 5 year career development plan for Dr. Pallavi Gopal to serve as a transition to successful independent physician-scientist. Dr. Gopal completed her clinical training in Anatomic Pathology and Neuropathology at the University of Pennsylvania (Penn), and is now developing an independent research and training program that will allow her to gain expertise in spatial and temporal dynamics of mRNA transport under physiological conditions and in disease. This proposal brings together diverse resources in RNA metabolism, molecular neuroscience and neuropathology and will provide superb training for Dr. Gopal to develop into an independent physician-scientist. Research will be performed under the mentorship of Dr. Erika Holzbaur, an internationally recognized expert in microtubule-based motors and real-time axon transport dynamics. This grant will provide protected time for Dr. Gopal to gain expertise in neuronal cytoskeletal, organelle, and RNA-protein dynamics through formal coursework, scientific seminars and meetings. The collaborative environment at Penn will foster utilization of novel techniques to conduct the proposed project and will provide Dr. Gopal with the training required to proceed towards a successful academic career. Amyotrophic lateral sclerosis (ALS) and front temporal lobar degeneration (FTLD) exist on two ends of a clinic pathologic spectrum but share clinical, genetic, and pathologic features. Ubiquitinated cytoplasmic inclusions composed of Tran's active response DNA-binding protein of 43 kDa (TDP-43) are a shared feature of sporadic ALS and the most common form of FTLD; there is concomitant loss of normal nuclear TDP-43 expression. Moreover, the discovery of disease-linked mutations in TDP-43 and other RNA processing proteins highlights altered RNA metabolism as a common pathogenic mechanism of neurodegeneration. However, our knowledge of how TDP-43 mislocalization disrupts its nuclear and cytoplasmic RNA processing functions and/or mediates toxicity in the cytoplasm is still incomplete. The research plan will utilize innovative approaches with real-time imaging techniques in primary neurons to test two main hypotheses: that loss of nuclear TDP-43 results in reduced dynamic flux of TDP-43 target mRNA and proteins in axons and that cytoplasmic redistribution of TDP-43 under pathological conditions results in mislocalization of TDP-43- associated mRNA. The specific aims are to: 1) Determine whether loss of nuclear TDP-43 function reduces axonal trafficking of synaptic proteins and organelle turn over and 2) Determine how (A) loss of cytoplasmic TDP-43 RNA binding function and (B) stress-induced cytoplasmic TDP-43 aggregation affect localization and trafficking of mRNA in axons and dendrites. These studies will provide temporal and spatial resolution of individual RNA transcripts in neurons in order to gain a clearer understanding of altered RNA metabolism in ALS/FTLD pathogenesis.