Scientists from the Salk Institute for Biological Studies have developed a technique to target and break down mutated mitochondrial DNA in mice.

The researchers investigated so-called mitochondrial diseases, wherein mutations happen in the DNA found in the mitochondria. These mutations are passed directly from mother to baby.

Some kids born with mitochondrial diseases may develop heart disease, muscle weakness and intestinal disorders, which could in turn lead to a shortened life expectancy.

The researchers discovered that this technique of gene editing may be successfully implemented in mouse eggs. After fertilization, these eggs could continue to produce fertile and healthy mice, with only a small part of the targeted mitochondrial DNA in their cells.

The technique also appears to work on a fusion of mouse-human cells injected with human mitochondrial DNA mutations inside the laboratory.

The study may be crucial in creating a separate procedure that prevents passing on mitochondrial mutations to offspring without the need for a donor egg.

The scientists developed a method to minimize the amount of mutation-carrying mitochondrial DNA. The technique was performed by inserting into the cells instructions to create a protein directed to the mitochondria then to cut the mitochondrial DNA in a particular part.

After their experiments in mice using this improved technique, they tried it on cells in the laboratory that contained human mitochondria with mutations that triggered either of the two mitochondrial diseases: neurogenic muscle weakness, ataxia and retinitis pigmentosa (NARP) or Leber's hereditary optic neuropathy and dystonia (LHOND). Both are rare human conditions that cause symptoms affecting vision, muscles and physical movement.

The scientists found they could adjust their technique to detect human mitochondrial mutations. It lowered the amount of mitochondrial DNA containing the NARP or LHOND mutations in hybrid egg cells in the laboratory.

The next step is to run preliminary laboratory tests on discarded human embryos and, if proven safe and effective, it could provide a simpler alternative to the mitochondrial transfer therapy recently approved in the UK.

The study is published in the journal Cell. The researchers were sponsored by the JDM Fund; G. Harold and Leila Y. Mathers Charitable Foundation; National Natural Science Foundation of China; Chinese Academy of Sciences; National Basic Research Program of China; Leona M. and Harry B. Helmsley Charitable Trust; Florida Department of Health; United Mitochondrial Disease Foundation; Muscular Dystrophy Association; and the U.S. National Institutes of Health.

Photo: Steve Jurvetson | Flickr

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