Researchers reveal plan to create infertile GM rats

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IT is a far more sophisticated solution than setting a trap or laying out poison-laced cheese.

Scientists say pest problem may soon be solved by releasing genetically engineered rats.

The University of Edinburgh says within two years rats could be made infertile by tweaking their genes, or made to have only male offspring.

The University of Edinburgh says within two years rats could be made infertile by tweaking their genes, or made to have only male offspring.

HOW IT WORKS 

Scientists say the creatures could be stopped from breeding using CRISPR/Cas 9 – a technique which works like ‘molecular scissors’ to snip away DNA.

This technique works to disrupt a fertility gene in rats, to make females infertile. It can also skew the sex ratio which makes some baby rats male with an XY pair of chromosomes and some female with an XX pair.

By ‘shredding’ the X chromosome, scientists have made almost 95 per cent of mosquito offspring male – cutting birth rates massively because there are not enough females to breed.

 

These laboratory rodents, released into the wild to pass on their mutant genes, could cut rat populations in cities like London, where the urban myth goes that residents are never more than six feet away from a rat.

GM mosquitoes are already being created in Australia to protect people from the malaria carried by the deadly insects. 

However the British scientists will be the first to try the technique out on mammals.

Gus McFarlane, co-author of a study on the solution, said: ‘There are obvious benefits of this gene drive strategy compared to current control measures that are really quite brutal – shooting, poisoning, trapping, kind of ‘bash over the head’ techniques.

‘It is more humane to cause a population decline with minimal animal suffering. 

It is species-specific, as you are only targeting the target species you plan to, and also potentially more cost-effective.’

There are believed to be tens of thousands of rats in Britain, which have caused devastation in certain areas. 

The remote island of Canna, off the coast of Scotland, was forced to spend around £500,000 and set 4,200 traps before finally becoming rat-free in 2008.

WHAT IS CRISPR-CAS9?

CRISPR-Cas9 is a tool for making precise edits in DNA, discovered in bacteria.

The acronym stands for ‘Clustered Regularly Inter-Spaced Palindromic Repeats’.

The technique involves a DNA cutting enzyme and a small tag which tells the enzyme where to cut.

By editing this tag, scientists are able to target the enzyme to specific regions of DNA and make precise cuts, wherever they like.

The CRISPR/Cas9 technqiue uses tags which identify the location of the mutation, and an enzyme, which acts as tiny scissors, to cut DNA in a precise place, allowing small portions of a gene to be removed

The CRISPR/Cas9 technqiue uses tags which identify the location of the mutation, and an enzyme, which acts as tiny scissors, to cut DNA in a precise place, allowing small portions of a gene to be removed

It has been used to ‘silence’ genes – effectively switching them off.

When cellular machinery repairs the DNA break, it removes a small snip of DNA.

In this way, researchers can precisely turn off specific genes in the genome.

The approach has been used previously to edit the HBB gene responsible for a condition called β-thalassaemia. 

Scientists say the creatures could be stopped from breeding using CRISPR/Cas 9 – a technique which works like ‘molecular scissors’ to snip away DNA.

This technique works to disrupt a fertility gene in rats, to make females infertile. It can also skew the sex ratio which makes some baby rats male with an XY pair of chromosomes and some female with an XX pair.

By ‘shredding’ the X chromosome, scientists have made almost 95 per cent of mosquito offspring male – cutting birth rates massively because there are not enough females to breed.

Edinburgh University’s Roslin Institute hopes to start trialling both techniques in a ‘contained and controlled’ rodent lab within two years.

Professor Bruce Whitelaw, principal investigator at Roslin Institute, where Dolly the sheep was famously cloned, said: ‘We have the makings of a technology that could reduce or eliminate a pest population in a humane and species-specific manner.

HOW IT COULD BE USED ELSEWHERE

If their approach is successful, the gene drives could potentially be applied to help control a range of other non-insect pest species, such as rabbits, mink and cane toads.

Currently, an older approach called ‘sterile insect technology’ is being used in some areas to fight mosquitoes. Intrexon’s Oxitec unit has already deployed its sterile male mosquitoes, whose offspring die when young, in Brazil.

But because Oxitec’s mosquitoes last only one generation, a vast number must be released to swamp their wild counterparts.

Existing approaches to fighting pests, particularly mosquitoes, have so far shown mixed success, with insecticide resistance increasing in many parts of the world and drugmakers struggling to develop good vaccines against complex diseases such as dengue.

 

‘We need more research to better understand the risks, and whether these can be mitigated, but we believe the potential benefits merit further investigation.’

The genetically modified rats would pass on their infertility or likelihood to have male offspring to the next generation, scientists believe. It means a mutant gene could spread throughout an entire population within as few as 10 generations.

Pest control costs the UK economy an estimated £1.2 billion each year, with the British Pest Control Association reporting more than 186,000 call-outs relating to rats in a single year.

The researchers stress that additional research to investigate the potential risks associated with gene drive technology would have to be carried out before the approach could ever be applied in the real world.

But if their approach is found to be successful, they say it could potentially be applied to help control other pest species, such as rabbits and cane toads.

 





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