New York, Oct 22 (IANS): Do you know why moderate tipplers suddenly become binge drinkers -- the answer, my friend, lies in the genes.

According to a study by the University of California, San Francisco (UCSF), a tiny segment of genetic material known as microRNA plays a central role in the transition from moderate drinking to binge drinking and other alcohol use disorders.

MicroRNA lowers levels of protective protein in a brain region important for the development of alcohol addiction.

Previous research in the laboratory of Dorit Ron, a professor in UCSF's department of neurology, had demonstrated that the level of a protein known as brain-derived neurotrophic factor, or BDNF, is increased in the brain when alcohol consumed in moderation.

In the new study, Ron and colleague Emmanuel Darcq, now at the McGill University in Canada, found that when mice consumed excessive amounts of alcohol for a prolonged period, there was a marked decrease in the amount of BDNF in a brain region important for decision making.

MicroRNAs lower the levels of proteins such as BDNF.

"Our results suggest BDNF protects against the transition from moderate to uncontrolled drinking and alcohol use disorders," Ron said.

In searching for potential therapies for alcohol abuse "it is important that we look for future medications that target drinking without affecting the reward system in general", the researchers concluded.

The study appeared in the journal Molecular Psychiatry.