The researchers say their finding that rare mutations might collectively play a large part in the development of common, yet complex, diseases such as hypertension also has implications for the diagnosis and treatment of such diseases as diabetes and schizophrenia.

"Collectively, common variants have explained a small fraction of the risk of most diseases in the population, as we would expect from the effects of natural selection,'' said Yale Professor Richard Lifton, who led the study with Daniel Levy, director of the National Heart, Lung and Blood Institutes's Framingham Heart Study. "The question this leaves open is whether many rare variations in genes will collectively account for a large influence on common disease.''

Lifton said the new study underscores the importance of sequencing the genome of many individuals in order to discover disease-causing mutations.

The research is reported in the journal Nature Genetics.