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Gene 'editing' technique shows promise

8 April 2005
By BioNews
Appeared in BioNews 303

A gene therapy technique that repairs faulty genes by 'editing' their DNA could lead to new treatments for inherited blood disorders and HIV (human immunodeficiency virus), say US researchers. The approach could help address safety concerns over current gene therapy methods, many of which rely on specially adapted viruses to deliver working genes to cells. The team, lead by researchers at Sangamo Biosciences in Richmond, California, published their results in the early online edition of Nature.

The scientists tested the technique on human immune cells growing in the laboratory, which had the genetic defect that causes severe combined immune deficiency (SCID). Children affected by SCID have a faulty gene that means their immune systems do not work properly, so their bodies cannot effectively fight infections. To repair the gene, the team put together a protein that could 'home in' on the section of DNA code that contained the fault. They then fused this protein to an enzyme that would snip the DNA at that specific point, and simultaneously inserted a new piece of correct DNA code into the cell - effectively carrying out a biological 'find and replace' process. The replacement DNA is incorporated into the gene via a naturally-occurring repair mechanism, called recombination.

The gene editing technique successfully corrected the faulty SCID gene in 18 per cent of the immune cells. The scientists now hope to use the approach on blood stem cells taken from SCID patients, to develop a new type of gene therapy for this disorder. As well as SCID, the technique could also be used to treat other hereditary blood diseases, such as sickle cell anaemia and thalassaemia. Edward Lanphier, president of Sangamo said: 'We can target any gene we want, go into human cells and correct mistakes'. The team also hopes to tackle HIV, by altering genes that make the proteins through which HIV gets into immune cells.

Previous SCID gene therapy treatment using viruses to deliver working genes has proved effective, but three children in a French trial for X-linked SCID developed leukaemia - one of whom has died. The cancer is thought to have been triggered by the insertion of the virus's genetic material into that of the immune cell, thereby switching on a cancer-causing gene. The new technique should avoid this problem, but there other potential concerns, cautions US geneticist John Wilson. It could be difficult to make the technology specific enough, and, as he points out, 'we don't want to be cutting up the genome willy-nilly'.

Sue Mayer, of the pressure group GeneWatch UK, called for the new gene editing approach to be regulated so that it would not be used for 'trivial' reasons. 'We sometimes overstate how many people would want to use it for that, but unless there are safeguards in place then the temptation will always be there', she told the Guardian newspaper. Lanphier said that the technique could potentially target genes not involved in disease, but added that he thought the reality is that 'people who apply it will do so for medical reasons'.

'Editing' technique can rewrite genes
The Guardian |  4 April 2005
'Gene-editing' technique cuts out diseased DNA
New Scientist |  4 April 2005
Genetic patch treats 'bubble-boy' disease
HealthDay News |  3 April 2005
Technique to Fix DNA Flaws Is Tested
The Washington Post |  4 April 2005
2 December 2013 - by Dr Rachel Montgomery 
A biotech start-up that will develop genome-editing therapies has received US $43 million investment from three venture capital firms...
11 November 2013 - by Dr Anna Cauldwell 
A molecular technique that enables any part of the human genome to be altered with extreme precision has been hailed by scientists as a breakthrough in genetics...
11 July 2011 - by Dr Caroline Hirst 
Scientists have, for the first time, successfully treated a blood disorder by repairing errors in the DNA of a living animal. Researchers from The Children’s Hospital of Philadelphia, together with California-based Sangamo BioSciences, have applied an innovative genome editing technique to treat haemophilia B, which affects around one in 30,000 boys and men...
31 August 2010 - by Alison Cranage 
Scientists have identified genetic changes responsible for the rare skin condition, ichthyosis with confetti (IWC). They also discovered that skin cells from patients with IWC can eliminate the genetic mutation that causes the disease...
13 March 2005 - by BioNews 
Doctors at Great Ormond Street Hospital (GOSH) for Children and the Institute of Child Health have successfully treated a second disease using pioneering gene therapy treatment. The four-year old boy who received the therapy was affected by ada-SCID, a life-threatening immune deficiency condition. He is now attending pre-school and living...
7 March 2005 - by BioNews 
The US Food and Drug Administration (FDA) has recommended that gene therapy treatments for an inherited immune disorder are limited to those who have no alternative. The move follows news that a third child in a similar French trial has developed leukaemia. The trial for X-linked severe combined immunodeficiency disorder...
31 January 2005 - by BioNews 
A gene therapy trial for an inherited immune deficiency disorder has been suspended again, following the appearance of complications in a third child. Eleven patients affected by X-linked severe combined immunodeficiency disorder (X-SCID) have so far been treated by the team, based at the Necker Hospital in Paris. While most...
14 June 2004 - by BioNews 
A French gene therapy trial halted after two participants developed leukaemia looks set to restart after a 22-month suspension, reports Nature. Scientists at the Necker hospital in Paris successfully treated nine children with an inherited immune system disorder called X-linked severe combined immune deficiency (X-SCID). But the trial, along...
21 July 2003 - by BioNews 
A second patient in a gene therapy trial taking place at Great Ormond Street Hospital in London has been successfully treated, his parents and doctors announced last week. Christopher Reid, now two years old, received gene therapy for the immune system disorder X-linked severe combined immune deficiency (X-SCID) in December...
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