Mutation hotspot in the desert

Researchers at the University of Oxford have discovered a giant mutation hotspot within the genome of a diabetes-prone rodent.

The sand rat Psammomys obesus, native to deserts of North Africa and the Middle East, eats low carbohydrate plants but is prone to obesity and type II diabetes if given normal food. It was long thought that this was because sand rats are missing a key switch gene, called Pdx1, which in humans controls the levels of insulin. 

Professor Peter Holland and Dr Adam Hargreaves, of the Department of Zoology, have proved the gene loss idea is wrong, but in doing so they uncovered a more interesting phenomenon. In a decade-long collaborative study with scientists from Bangor, London, Denmark, USA and China, they discovered that the sand rat Pdx1 DNA has been affected by many small mutations, compromising the gene but not totally removing it. 

But strikingly, the researchers also discovered that a whole slew of genes on the same chromosome as Pdx1 have been hit by hundreds of small mutations, almost all of which convert A and T nucleotides to G and C.  

Professor Holland said: “The discovery of a super-hotspot of mutation on one chromosome shatters the idea that mutation rates are roughly equal between genes and that natural selection is the only driver of the direction of evolution.” 

“Our speculation is that hotspots of high mutation rate might be an under-appreciated force in biasing the direction of evolution.”

Read the full paper here: