Geneticists discover technique to tackle mutant DNA

Scientists at the University of Rochester believe they have found a way to alter the genes that can cause disease

guardian.co.uk, Ian Sample, science correspondent, Wednesday 15 June 2011

Mutations in DNA lead to an estimated one third of all genetic
disorders. Photograph: Mopic/Alamy

Scientists have hit on a genetic trick that opens up fresh avenues for the treatment of devastating diseases, such as cystic fibrosis, muscular dystrophy and certain forms of cancer.

The technique corrects glitches in genetic machinery that cause the body to make faulty versions of proteins that can lead to the onset of disease.

Although the work is at an early stage, the strategy represents a radical new approach to tackling mutations that give rise to an estimated one third of all genetic disorders.

"This is a really powerful concept that can be used to try to suppress the tendency of individuals to get certain debilitating, and sometimes fatal genetic diseases," said Robert Bambara at the University of Rochester Medical Centre, who was not involved in the study.

Proteins are the workhorses of the body and carry out all of the functions necessary for life, from metabolising food to building cells and directing immune attacks on unwelcome invaders. Taken together, the cells of the body make around 20,000 different proteins.

The instructions to make human proteins are carried by around 25,000 genes that are found in almost every cell. To make a protein, each "letter" of a gene must be copied into a single strand of genetic material called messenger RNA (mRNA). The cell then takes this mRNA and uses it as a blueprint to build the protein in a process called translation.

But the business of making proteins does not always proceed smoothly. Mutations in genes or mRNA can give rise to faulty proteins that in many cases trigger disease.

John Karijolich and Yi-Tao Yu at the University of Rochester Medical Centre focused on a type of mutation that causes strands of mRNA to contain premature "halt" signs called stop codons. These order cells to stop making proteins before the job is finished. As a result, affected cells churn out short and incomplete proteins.

Writing in the journal, Nature, the scientists describe a series of experiments in which they used short strands of RNA to correct faulty mRNA, by switching unwanted stop signs into "go" signs. To their surprise, treated cells began to produce healthy, full-length proteins again.

"This is a very exciting finding," Yu said. "No one ever imagined that you could alter a stop codon the way we have and allow translation to continue uninterrupted like it was never there in the first place."

"Our work is still really early with regard to clinical application," Yu told the Guardian. "However, we believe it will eventually offer a potential therapeutic option for premature stop codon-caused diseases, such as cystic fibrosis and muscular dystrophy."

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