Characterizing mitochondrial neurodegenerative diseases in the zebrafish model
University of California, Los Angeles
Department of Chemistry and Biochemistry
Defects in mitochondrial biogenesis result in inherited mitochondrial diseases that are typically referred to as mitochondrial myopathies and neuropathies. However, suitable animal models to facilitate understanding the molecular basis for these diseases are limited. To investigate the physiologic impact of neurodegenerative, mitochondrial diseases, zebrafish is an excellent vertebrate model. Zebrafish lines have been generated in which mitochondria are tagged with a fluorescent protein in heart, brain, and neurons. These tissues are typically affected by mitochondrial disease due to their high energetic requirement. Subsequently, these lines are used for phenotypic characterization of mitochondrial dysfunction when mitochondrial assembly pathways are disrupted by gene-editing methods or treatment with specific molecules that attenuate mitochondrial protein import. Mitochondrial morphology and mitochondrial trafficking in the axons, as well as axonal development, are monitored by confocal microscopy and selective plane illumination microscopy (SPIM). The small molecule inhibitor MitoBloCK6 impairs neural development. Specifically, the neurons are less branched and mitochondrial movement is impaired. However, this phenotype can be rescued by the addition of the reductant, N-acetylcysteine. This mitochondrial import pathway is important in amyotrophic lateral sclerosis (ALS), and these studies suggest that treatment with antioxidants may reduce the progression of this disease. To investigate the molecular basis of these mitochondrial diseases, I am using the TALEN and CRISPR/Cas9 systems to target specific mitochondrial genes that are linked to neurodegeneration. My goal is to connect mitochondrial dysfunction to the subsequent neurodegenerative effects. Using zebrafish to recapitulate the resulting disease phenotypes from targeted protein mutations will generate a model organism that has more clinical relevance for studying mitochondrial protein translocation and the degenerative consequences that arise when the import system is compromised. Long-term, these studies will provide a better molecular understanding of the role of mitochondria in neurodegenerative diseases including Parkinson’s disease and Alzheimer’s disease.