8/01/2008 PERMALINK
Eroded telomeres causes early aging syndrome Each time a cell divides, the protective caps at the ends of chromosomes shorten — and when these caps are gone, you die. Telomeres are partially rebuilt with an enzyme called telomerase. When researchers genetically engineered mice that didn’t produce telomerase, the mice had very short telomeres but didn’t show any signs of early aging disease, particularly its hallmark: bone marrow failure. Next they made mice that lack POT1b, a protein that protects telomeres from getting degraded. Without POT1b, mice do not show the signs and symptoms of dyskeratosis congenita, but the telomeres shorten so fast that telomerase is incapable of keeping up with the loss and the mouse die of the disease. When the mice that lacked POT1b were bred with mice that lacked telomerase, the offspring died. Together, these results suggest that in patients suffering from dyskeratosis congenita, the enzyme telomerase can’t elongate telomeres as fast as the nucleases chew them away ... more