Tuesday, June 19, 2007

Cells Need to Talk to Each Other

It seems clear that both aging and cancer are at least in part due to the accumulation of mutations in individual cells. Seen in the abstract, in terms of information, this is surprising. Our genetic information, after all, is massively redundant; mutations aside and ignoring a few special cases, every cell contains a copy of the same genotype. All a cell has to do in order to identify a particular sequence as a mutation is to check with two or three of its neighbors and see if they have it.

This suggests a possible strategy for life extension. Once our technology is good enough—not, unfortunately, any time soon—create some mechanism to exploit the redundancy, some way of identifying mutations by majority vote and eliminating them.


At 2:07 PM, June 19, 2007, Anonymous Anonymous said...

Maybe lack of communication is explained by the evolutionary necessity of cell differenciation.

Not a biologist, just a random guess :)

At 4:54 PM, June 19, 2007, Blogger jimbino said...

Since nature loves cancer just as much as the alternative, if you get zapped by a cosmic ray that causes a mutation, your scheme might just result in the adjacent cells' becoming cancerous as well.

This is the well known Game of Death.

At 5:16 PM, June 19, 2007, Anonymous Anonymous said...

I think the assumption is that the sane cells would be identical while the cells zapped by the mutation would not... like raid.

At 6:07 PM, June 19, 2007, Blogger David said...

Doesn't the human body already do this? Cells are checked by themselves, their neighbors, and the immune system to confirm that they're good. If they fail the check, they're scheduled for termination. Organ transplant rejection is an example of this mechanism in action. Tumors result when a cell mutates in such a way that it ignores the termination requests.

At 4:46 AM, June 20, 2007, Anonymous Anonymous said...

Not quite ;-) There's the blueprints (DNA) and the infrastructure (proteins and RNA). One of the jobs of the infrastructure is to maintain the blueprints. Too much damage to the infrastructure, and the blueprint is useless (there's no one left who knows how to properly read it). Damage to the blueprint occurs not just by mutations (changing the words on the blueprint) but by strand damage (tearing a couple pages out of the blueprint).

How much of cancer is the result of any of these factors is a matter of constant debate (or rather hypothesis formation and falsification ;-)

I highly recommend the works of Matt Ridley on this.

At 7:06 AM, June 20, 2007, Blogger Jim Lippard said...

One problem with suppressing all mutation is that mutations and diversity of genome are a good thing in the long run. What is detrimental in one environment can be beneficial in another.

At 11:59 AM, June 20, 2007, Blogger William said...

I'm glad that non-scientists are thinking about these things, and you seem fairly well-informed, but there's a layer of subtlety you're missing.

Mutation happens all the time, so it's not just a question of "is it different?" It's when the mutation happens in such a way that the cell stops listening to signals, loses internal controls, and something else happens that you get a malignant cell.

At 6:20 PM, June 21, 2007, Anonymous Anonymous said...

Majority vote? Hah! Don't extend the tyranny of democracy to the cellular level - let each cell decide for itself if it wants to mutate or not. After all, each cell is the private property of its individual nucleus!

At 11:03 AM, June 22, 2007, Anonymous RKN said...

Even imagining such a future technology, I wouldn't probe the genome. For the reasons william mentioned, but also because in eukaryotes DNA would be structurally unavailable to any exogenous "mechanism" - it's wrapped up tight around histones and tucked away in the nucleus. And for biologically good reasons, too. I'd instead probe the proteome - misfolded protein(s), markers of disregulation, etc. - before I'd ever suggest trying to compare genomes. And indeed there are a number of causes of important human cancers that don't involve a somatic mutation.

At 9:01 AM, June 25, 2007, Blogger Karl said...

There was a story in Analog (I believe) in which some people had received genetic modifications that greatly extended their lives. It involved a new set of cellular machines that implemented a check sum on the cell's DNA.

If, during cell replication, the checksum didn't match the value stored in the DNA, the cell was destroyed. Upside: no cancer, and greatly reduced senescence. Downside: it couldn't handle meiosis, so reproduction couldn't occur.

Nanotech that does error correction by comparing DNA sequences among three or more cells is an obvious fix. It works on computer memory, and it ought to work on cells as well.


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