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Flatworms Defy Aging Through Cell Division Tricks
An anonymous reader writes "Researchers from The University of Nottingham have demonstrated how a species of flatworm overcomes the aging process to be potentially immortal. The discovery, published (abstract; full text PDF) in the Proceedings of the National Academy of Sciences, is part of a project funded by the Biotechnology and Biological Sciences Research Council and Medical Research Council and may shed light on the possibilities of alleviating aging and age-related characteristics in human cells."
After finding the gene for telomerase synthesis in the worms, the researchers were able to observe that the worms "...dramatically increase the activity of this gene when they regenerate, allowing stem cells to maintain their telomeres as they divide to replace missing tissues."
That would be all of it.
"Unlike other bilaterians, they have no body cavity, and no specialized circulatory and respiratory organs, which restricts them to flattened shapes that allow oxygen and nutrients to pass through their bodies by diffusion."
Here is a video from the researchers themselves.
http://www.test-tube.org.uk/videos/pages_aziz_immortal_worms.htm
In humans, telomeres limit cells to ~50 divisions, which is probably related to how DNA replication is only 99.9998% accurate. After that many divisions, the genome is 0.001% different from when it started, which is one error per 10,000 base pairs, or an error in 1/3 of all genes. This is in addition to the slow rate of spontaneous mutations you accumulate over your lifetime.
In general, fatal mutations don't matter, the stem cell will just divide again (or be dead), and cells are specialized so only a small number of genes are relevant. Furthermore, cells work together, so if two nearby cells have different lineages then they have different errors, and can likely compensate for each other. Still, you don't want too many errors in your cell replication control genes (i.e. protooncogenes ==> cancer), nor can cells function well with a tremendous number of errors (i.e. "aging"). Telomeres also help divvy-up the workload among stem cells so the most eager doesn't monopolize the work.
For flatworms, all this likely entails a fast mutation rate. So what if 90% of its offspring die? The one that takes hold in a new host can produce thousands of offspring, and quickly changing their immunologic profile increases the odds of that.
The Immortal Life Cycle of Turritopsis, with diagrams http://9e.devbio.com/preview_article.php?ch=2&id=6 __ Inmmortal human cells. http://www.smithsonianmag.com/science-nature/Henrietta-Lacks-Immortal-Cells.html
telomerase - it's just restricted to the germ line
In humans, telomeres limit cells to ~50 divisions, which is probably related to how DNA replication is only 99.9998% accurate. After that many divisions, the genome is 0.001% different from when it started, which is one error per 10,000 base pairs, or an error in 1/3 of all genes. This is in addition to the slow rate of spontaneous mutations you accumulate over your lifetime.
Where did you get your numbers? Human DNA replication (in normal cells with no damage) is 99.99999999% accurate (i.e. about 1 mutation per 10^-10 base pairs). Please do not mod parent informative for this misinformative post!