Analysis of autophagy and mitochondrial homeostasis in a human iPS model of NCL

Massachusetts General Hospital, Boston MA

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Abstract

DESCRIPTION (provided by applicant): As a physician-scientist with training in clinical and molecular pathology, I plan to pursue my long-standing interest in inherited forms of neurodegeneration and develop an independent, R01-funded academic career at the Massachusetts General Hospital (MGH). My graduate background on the relationship between protein processing defects and neurodegeneration provides a solid foundation for my proposed work on the role of autophagy in the neuronal ceroid lipofuscinoses (NCLs; also known as Batten Disease). The MGH-CHGR (Center for Human Genetic Research) Joint Program in NCL Disorders will serve as the focal point of my career development and training activities. The Joint Program includes (1) the basic research labs of my primary mentor Dr. Susan Cotman and my co-mentor Dr. Marcy MacDonald, (2) a clinical component (MGH Batten Disease Center of Excellence) directed by my co-mentor Dr. Katherine Sims, (3) a reference lab for NCLs and other rare neurologic disorders, and (4) a tissue culture core facility that includes an IRB-approved bio repository of fibroblast and lymphoblastic cell lines from NCL probands and family members. The NCLs comprise a group of at least 12 distinct, currently untreatable lysosomal storage diseases with clinical features that include progressive motor and cognitive decline, retinal degeneration and visual loss in most cases, seizures, movement disorder, and eventual premature death. I propose to build on insights gained from a genetically precise knock-in murine model of NCL that replicates the most common mutation among the NCL disorders. Cerebellar cell lines derived from this model have demonstrated that end-stage pathology is preceded by impairments in autophagy as well as by altered mitochondrial morphology, decreased basal ATP levels, increased sensitivity to oxidative stress, and altered transcriptional regulation of mitochondrial oxidative phosphorylation under basal conditions. In this application, I propose to use novel, human iPS-derived neuronal culture models of NCL to address the hypothesis that impaired autophagic turnover of mitochondria (mitophagy), and thus impaired mitochondrial quality control, is a critical early component of pathophysiology in NCL patients. Specifically, I will investigate autophagy and mitochondrial biology in this neuronal system by electron microscopy, dynamic imaging of mitophagy, and measurement of bioenergetics parameters, including basal and maximal respiratory capacity. In addition, I will use an extensive database that I developed to identify atypical and molecularly undefined NCL patients with early clinic pathologic evidence of mitochondrial disease. I will use next- generation sequencing technology to identify potential causal variants in a core subset of these patients, an approach that will likely generate new hypotheses about the genetic interaction between NCL and mitochondrial biology and suggest novel targets for therapeutic intervention.