Worm life span set by chromosome tips.

Telomeres, which are caplike DNA structures at the tips of chromosomes, have long been suspected of playing a pivotal role in aging. A new study of worms adds to the case. Worms with longer telomeres live longer than do counterparts with shorter telomeres, Korean researchers report in the June Nature Medicine.

With every division, a cell's chromosomes get shorter by shedding portions of their telomeres (SN: 11/25/95, p. 362). Researchers have theorized that when telomeres get too short, cells enter a nondividing state called senescence. The effects of aging, in part, may result from the buildup of senescent cells (SN: 1/17/98, p. 37).

By adding a gene that promotes the lengthening of telomeres to some worms of the species Caenorhabditis elegans, Junho Lee of Yonsei University in Seoul and his coworkers created groups of worms that varied only in their telomere length. The ones with longer telomeres lived on average 24 days, or about 20 percent longer than unmodified worms. For reasons that aren't clear, the worms with longer telomeres were also more resistant to the detrimental effects of hear exposure.