"D. melanogaster" is often used for life extension studies, such as to identify genes purported to increase lifespan when mutated. "D. melanogaster" is also used in studies of aging. Werner syndrome is a condition in humans characterized by accelerated aging. It is caused by mutations in the gene WRN that encodes a protein with essential roles in repair of DNA damage. Mutations in the "D. melanogaster" homolog of "WRN" also cause increased physiologic signs of aging, such as shorter lifespan, higher tumor incidence, muscle degeneration, reduced climbing ability, altered behavior and reduced locomotor activity.