Mitochondrial Physiology Network 10.9: 103 (2005) - download pdf

Knockdown of COX5a in zebrafish phenocopies aspects of human COX deficiency.

Katrina Baden, K Guillemin, R Capaldi

University of Oregon Institute of Molecular Biology – kbaden@darkwing.uoregon.edu

    Zebrafish offer significant genetic, physiologic, and economic benefits as a model system in which to study human disease [1].  While mouse has been the traditional animal model of mitochondrial disease, we believe zebrafish will be a powerful new system in which to investigate outstanding questions in the field of mitochondrial pathophysiology [2].

    In humans, defects in mitochondrial energy production, particularly by oxidative phosphorylation (OXPHOS), affect a wide variety of tissues including central and peripheral nervous system, ocular, cardiac, gastrointestinal, and skeletal muscle [2-3].  Deficiency in cytochrome c oxidase (COX), an integral part of the OXPHOS respiratory chain, is a component of many mitochondrial disorders [4].  We are using a morpholino antisense oligonucleotide to the COX5a subunit (COX5a-MO) to knockdown expression of COX5a and recapitulate human COX deficiency syndromes in zebrafish.  Utilizing monoclonal antibodies we are able to follow tissue expression of COX5a in wildtype and MO-injected fish by immunohistochemistry and western blot, while monitoring the levels of COX using a monoclonal antibody against subunit 1 and total mitochondrial content in cells with an antibody to porin.

    Preliminary results of COX5a knockdown in the developing zebrafish indicate that many of the tissues affected in humans with COX deficiency are also affected in zebrafish.  Morpholino knockdown of COX5a results in stunted growth, motility impairment, pericardial edema, brain and eye abnormalities, failure to inflate the swim bladder, and no gastrointestinal tract development.  The zebrafish model of COX deficiency will be useful for investigating the molecular and cellular basis of mitochondrial disease.            

1.  Grunwald D, Eisen J (2002) Headwaters of the zebrafish – emergence of a new model vertebrate. Nat. Rev. Genet. 3: 717-24.

2.  Wallace D. (2001) Mouse models for mitochondrial disease. Am. J. Med. Genet. 106: 71-93.

3.  Zeviani M (2001) The expanding spectrum of nuclear gene mutation in mitochondrial disorders. Cell. Dev. Biol. 12: 407-416.

4.  DiMauro S, Bonilla E, Davidson M, Hirano M, Schon E (1998) Mitochondria in neuromuscular disorders. Biochim. Biophys. Acta 1366: 199-210.