Could gene editing end the obesity crisis? Tweaking DNA in people who want to lose weight can help to curb their appetite
- Scientists located the genes using CRISPR, a tool for finding and editing DNA
- They used a new technique called CRISPR-A to slightly tweak some genes
- The system differs from the former because it doesn’t cut genes to replace them
- Instead it amplifies the activities of certain selected genes to achieve its results
- Team found that mice were slimmer after amplifying copy of the SIM1 gene
Scientists are working on a method that will modify the genes of people who are trying to lose weight in a bid to tackle the obesity crisis.
Researchers say that by tweaking CRISPR, a tool for making edits to DNA, the cells could be changed to prevent people from being tempted by calorific treats.
This will be done by using CRISPR-A, a new technique, with the ‘A’ standing for activation – used to heighten genes that suppress appetite .
The system differs from CRISPR in that it doesn’t make cuts to the genome, but amplifies the activities of certain genes.
Scientists are working on a method that will modify the gene expression of people who are trying to lose weight in a bid to tackle the obesity crisis. The researchers say that by tweaking CRISPR, a tool for finding DNA sequences (stock image)
HOW DOES CRISPR DIFFER FROM CRISPR-A?
CRISPR, or CRISPR-CAS9? allows researchers to easily alter DNA sequences and modify gene function.
Its many potential applications include correcting genetic defects.
It also treats and prevents the spread of diseases and improving crops.
The use of this technique raises ethical concerns and potential consequences of tampering with genomes.
CRISPR-A differs from conventional CRISPR in that it doesn’t make cuts to the genome.
It retains CRISPR’s guidance system, which can be programmed to find a particular DNA sequence, but replaces the molecular scissors with a ‘volume control knob’.
When CRISPRa finds its target, it amplifies the activity of that gene. No edits are made.
Source: Live Science and The University of California
CRISPR is usually used to remove or ‘knock out’ a particular gene, but the new technique replaces the ‘molecular scissors with a volume control knob’.
The method has the same guidance system as CRISPR, which is used to find a particular DNA sequence but when the a version targets the genome, it ramps it up.
Navneet Matharu, who led the study, said that the CRISPR-a could potentially provide a cure for obesity and other diseases.
In the case of weight loss, the study said that the researchers were able to achieve long lasting weight control without making a single edit to the genome.
The authors of the study, by scientists from the University of California, tested on mice with genetic mutations which make them more likely to gain weight.
They used CRISPR to locate the genetic mutation in the mice that makes them predisposed to gaining weight.
By tweaking the activities of those genes, the result was that these mice were slim.
CRISPR relies on the fact that mammals have two copies of every gene, one from each parent.
There are at least 660 genes where a mutation in one copy appears to be linked to disease.
CRISPR-A differs from CRISPR in that it doesn’t make cuts to the genome, but amplifies the activities of certain genes that suppress hunger. It doesn’t cut and replace genes, it modifies and amplifies them with a ‘volume control knob’ (stock image)
SIM1 is the gene that plays the role in regulating hunger, mutations of which have been observed in severely overweight patients.
When both copies are working, people and mice are able to limit their food intake whereas in other cases the set of genes could have a mutation rendering one copy useless and the other not being able to provide a sufficient feeling of fullness.
‘Mice that were missing one copy of the SIM1 gene received the CRISPR-A injections at four weeks of age and maintained a healthy body weight.
Mice that didn’t receive CRISPR-A injections couldn’t stop eating. They started gaining weight at six weeks of age, and by the time they were ten weeks old, they were severely obese.’
Clinical trials on people are probably years away but Dr Matharu believes that CRISPR-A could provide ‘a potential cure for certain forms of obesity as well as hundreds of other diseases’.
The study was published in the journal Science.
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.
The CRISPR/Cas9 technique 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
By editing this tag, scientists are able to target the enzyme to specific regions of DNA and make precise cuts, wherever they like.
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.