Some individuals react coolly to stressful events, whereas others slip into depression. Work in mice suggests that chemical modifications to the DNA may explain the difference.

Shusaku Uchida and Yoshifumi Watanabe at Yamaguchi University in Japan and their colleagues subjected two genetically distinct strains of mice to chronic stress and then measured various proteins involved in neuronal growth and maintenance. The strain known to succumb to stress had lower than normal levels of a protein called GDNF in the brain's striatum. The resilient strain had higher amounts.

The team found that histones — proteins that package up DNA and regulate gene transcription — on a section of the Gdnf gene were modified differently between the two strains. This led to Gdnf repression in the susceptible mice and increased expression in the more resilient strain.

Neuron 69, 359–372 (2011)