'Early bird' sleep disorder gene discovered

US researchers have identified an altered gene that causes people to go to bed early and wake up before dawn. People with the condition, called familial advanced sleep phase syndrome (FASPS), do not usually sleep any more or less than others - just at different times. The new study, published in Nature, could lead to new ways of tackling disrupted sleep patterns caused by jet lag or shift working. The gene could also play a role in depression, say the team.

The group discovered the gene by studying an extended family in which five members were affected by FASPS. They then bred mice with the altered version of the gene, and found that the animals showed the same disrupted sleeping patterns as humans with the disorder. Unexpectedly, however, the researchers obtained the opposite result when they bred fruit flies with gene mutation. The findings show that although insects and mammals share similar proteins that make up the body's internal clock, they work in different ways.

The identification of the gene, called CK1 delta, provides a window on the body's internal biological clock or 'circadian rhythms'. According to lead study author Ying-hui Fu of the University of California, these rhythms 'may have a fundamental role in numerous behaviours'. The gene makes a protein called casein kinase 1 delta, which is responsible for affecting the activity of many other proteins. Fu said the group may investigate its involvement in novelty-seeking behaviour, learning and memory, as well as depression.

The researchers think that around 3 in every thousand people have the altered gene, with many changing their lifestyle to fit the condition. Team member Louis Ptacek, of the Howard Hughes Medical Institute in Maryland, said that some would never visit a doctor about their sleeping patterns because they aren't troubled by it. 'Often they have adjusted and accommodated their jobs to match their ability' he said, adding 'but others are bothered by being out of phase with the rest of the world'. The researchers say that the affected mice could now be used to test new drug treatments aimed at correcting sleep disturbance.