Abstract
The sand rat Psammomys obesus is a gerbil native to deserts of North Africa and the Middle East1. Sand rats survive with low caloric intake and when given high carbohydrate diets can become obese and develop type II diabetes2 which, in extreme cases, leads to pancreatic failure and death3,4. Previous studies have reported inability to detect the Pdx1 gene or protein in gerbils5–7, suggesting that absence of this key insulin-regulating homeobox gene might underlie diabetes susceptibility. Here we report sequencing of the sand rat genome and discovery of an extensive, mutationally-biased GC-rich genomic domain encompassing many essential genes, including the elusive Pdx1. The sequence of Pdx1 has been grossly affected by GC-biased mutation leading to the highest divergence observed in the animal kingdom. In addition to molecular insights into restricted caloric intake in a desert species, the discovery that specific chromosomal regions can be subject to elevated mutation rate has widespread significance to evolution.
