Genetic therapy to nip inherited diseases in bud

August 27th, 2009 - 5:31 pm ICT by IANS  

Washington, Aug 27 (IANS) Researchers believe they have developed one of the first forms of genetic therapy to nip inherited diseases in the bud.
Specifically, the therapy would counteract diseases inherited by kids from mothers, through mutated DNA in cell mitochondria. They are tiny energy-producing structures in the cell, sometimes known as its power plants or batteries and also carry their own genetic material.

“We believe this discovery in non-human primates can rapidly be translated into human therapies aimed at preventing inherited disorders passed from mothers to their children through the mitochondrial DNA,” said Shoukhrat Mitalipov, study co-author.

Mitalipov, associate scientist at the Oregon Health & Science University’s (OHSU) Oregon National Primate Research Centre (ONPRC), said these inherited disorders are certain forms of cancer, diabetes, infertility, myopathies and neurodegenerative diseases.”

“Currently there are 150 known diseases caused by mutations of the mitochondrial DNA, and approximately one out of every 200 children is born with mitochondrial mutations,” he said.

When an egg cell is fertilised by a sperm cell during reproduction, the embryo almost exclusively inherits the maternal mitochondria present in the egg.

This means that any disease-causing genetic mutations that a mother carries in her mitochondrial DNA can be passed on to her offspring.

The method developed by OHSU researchers transfers the mother’s chromosomes to a donated egg that has had its chromosomes removed, but which has healthy mitochondria, thereby preventing the disease from being passed on to one’s offspring.

Here is how the OHSU researchers’ method works: Scientists collected groups of unfertilised eggs from two female rhesus macaque monkeys (monkeys A and B).

They then removed the chromosomes, which contain the genes found in the cell nucleus, from the eggs of monkey B, and then transplanted the nuclear genes from the eggs of monkey A into the eggs of monkey B.

Then the eggs from monkey B, which now contained their own mitochondria but monkey A’s nuclear genes, were fertilised. The fertilised eggs developed into embryos that were implanted in surrogate monkeys.

The initial implantation of two embryos resulted in the birth of healthy twin monkeys, nicknamed “Mito” and “Tracker” (in reference to the procedure used for imaging of mitochondria). These monkeys are the world’s first animals derived by spindle transfer.

Follow-up testing showed that there was little to no trace of cross-animal mitochondrial transfer using this procedure. This demonstrates that the researchers were successful in isolating nuclear genetic material from mitochondrial genetic material during the transfer process.

“In theory, this research has demonstrated that it is possible to use this therapy in mothers carrying mitochondrial DNA diseases so that we can prevent those diseases from being passed on to their offspring,” added Mitalipov.

“We believe that with the proper governmental approvals, our work can rapidly be translated into clinical trials for humans, and, eventually, approved therapies,” he said, according to an OHSU release.

The research was published in the Wednesday advance online edition of Nature and is also scheduled for publication later.

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