First Animal Model Of Mitochondrial Disease Produced

Animal models can now be made for practically all monogenic disorders, most of which result from mutation of genes in the nuclear genome. The mitochondrial genome resides within cytoplasmic organelles called mitochondria. These are essential mini-power plants fueling cellular processes through biochemical reactions collectively known as the respiratory chain. Although many of the proteins involved in these reactions are encoded in the nuclear genome, most human disorders attributable to a defective respiratory chain are due to mutations in the mitochondrial genome. Animal models of such disorders were thought to be impossible to develop, due to difficulties in introducing and maintaining DNA in mitochondria.

A study by Jun-Ichi Hayashi and colleagues (of Tsukuba University in Japan), has now produced the first animal model of mitochondrial disease [Nature Genetics - October 2000]. In a technical tour de force, the authors exploited mitochondrial mutations that accumulate in ageing mice. They collected mutant mitochondria in small vesicles produced at neuronal synapses and, to obtain greater numbers, fused the vesicles with a special cell line that lacks its own mitochondria. In turn, they fused the hybrid cells to fertilized eggs, and implanted the products into surrogate mother mice. They thereby obtained living progeny with mutant mitochondria. As Eric Shoubridge (of Montreal Neurological Institute) explains in an accompanying News & Views article, the mouse model has interesting similarities and differences with people suffering from mitochondrial disorders. Mutations in mitochondrial DNA are known to cause diverse encephalomyopathies, which can lead to heart dysfunction or total paralysis and are sometimes associated with diabetes and hearing loss. The new technology should provide insights into the still-mysterious laws of mitochondrial propagation. The study also indicates that there are human disorders in which the role of mitochondria might have been overlooked, such as some forms of renal failure.

CONTACTS:
(Author)
Dr. Jun-Ichi Hayashi
Inst of Biological Science
University of Tsukuba
Tsukuba, Japan
Telephone: +81 (298) 53 6650
Fax: +81 (298) 53 6614
E-mail: jih45@sakura.cc.tsukuba.ac.jp

(News & Views)
Dr. Eric Shoubridge
Montreal Neurological Inst
Montreal, Quebec, Canada
Telephone: +1 (514) 398 1997
Fax: +1 (514) 398 1509
E-mail: eric@ericpc.mni.mcgill.ca

(C) Nature Genetics press release.

Message posted by: Trevor M. D'Souza