Researchers use this 1 millimeter-long soil roundworm that feeds on bacteria mainly because it is simple, easy to grow in bulk populations, and is quite convenient for genetic analysis.
When these scientists began their work almost nothing was known about worm telomeres. "We had to start at the very beginning. But now we know that C. elegans is the perfect model organism to study telomere biology since their regulation is similar to human telomeres," says first author Marcela Raices, a post-doctoral researcher in Karlseder's lab.
Many cells in our body keep dividing throughout life (e.g., those that line our digestive tract, blood, and immune cells) because they must be replaced over time. When these cells' telomeres reach a critically short length, however, they can no longer replicate. The cell's structure and function begin to fail as it enters this state of growth arrest, called replicative senescence.
"But even in very old people, blood cells, which divide continuously, don't have critically short telomeres. In humans and, as we know now, in worms, telomere length is certainly not a limiting factor for lifespan," says Karlseder.
The Salk team, which also included graduate student Hugo Maruyama, found that despite the close correlation of telomere length and cellular senescence in mammalian cells, worms with long telomeres were neither long lived, nor did worm populations with short telomeres exhibit a shorter life span. On the other hand, long-lived and short-lived mutant worms could have them either way without any effect on their lifespan. When Raices monitored telomere length over the full lifespan of worms and under stress, a situation reported recently at another laboratory to shorten telomeres in humans, she found absolutely no change.
"For successful a