1 Gene Lost = 1 Limb Regained? Scientists Demo. Mammalian Regeneration Thru Single Gene Deletion

[Demeter]

http://www.sciencedaily.com/releases/2010/03/100315161913.htm

A quest that began over a decade ago with a chance observation has reached a milestone: the identification of a gene that may regulate regeneration in mammals. The absence of this single gene, called p21, confers a healing potential in mice long thought to have been lost through evolution and reserved for creatures like flatworms, sponges, and some species of salamander.

In a report published in the Proceedings of the National Academy of Sciences, researchers from The Wistar Institute demonstrate that mice that lack the p21 gene gain the ability to regenerate lost or damaged tissue.

Unlike typical mammals, which heal wounds by forming a scar, these mice begin by forming a blastema, a structure associated with rapid cell growth and de-differentiation as seen in amphibians. According to the Wistar researchers, the loss of p21 causes the cells of these mice to behave more like embryonic stem cells than adult mammalian cells, and their findings provide solid evidence to link tissue regeneration to the control of cell division.

"Much like a newt that has lost a limb, these mice will replace missing or damaged tissue with healthy tissue that lacks any sign of scarring," said the project's lead scientist Ellen Heber-Katz, Ph.D., a professor in Wistar's Molecular and Cellular Oncogenesis program. "While we are just beginning to understand the repercussions of these findings, perhaps, one day we'll be able to accelerate healing in humans by temporarily inactivating the p21 gene."

[xchrom]

1. wow. nt

[ret5hd]

2. So, if I understand correctly... (please correct me if I am wrong)...

Republicans are the result of a combination of:
1) a hyperactive p21 gene

and

2) being dropped on their head as a child

[DavidDvorkin]

3. I assume that having the gene confers some advantage

If so, then let's hope that temporarily deactivating it wouldn't cause serious problems.

[txlibdem]

5. That's not how evolution works

Only genes that improve chances for procreation are selected for via evolution. This gene seems to be a wash; a scabbed-over wound could protect against germs entering the body but regrowing a lost limb would enable a person to "get back into the race" to compete for mates. My guess is that humans who lost a limb or had a serious injury probably died anyway (can't run from predators as fast, can't climb trees to get to the fruit) so this gene had no chance to impact survival in early Man.

[DavidDvorkin]

6. Isn't that the same as what I said?

The gene confers an advantage, so persists.

[txlibdem]

8. You misunderstood

I posted that the inactive gene had no chance to confer any evolutionary advantage so it renders itself moot. Worse, the gene when active causes scabbing, prevents infection, and gives a short-term benefit for those that survive. Those who would most be helped by an inactive gene, those who lost a limb or had a serious injury, would die before the limb grew back or they were otherwise back to full health: the inactive gene could not pass itself along to offspring and would be selected out of our gene pool.

Once society developed, the injured could have been protected and fed by other members of their family or extended group while their limb grew back, yes, but our genes were pretty much set in stone by that time.

[On the Road]

10. txlibdem is Not Explaining Himself or Herself

but I believe what he or she means is that evolution perpetuates advantages in breeding, not advantages in pure survival.

Of course, survival in Darwinian terms means passing your genes on to the next generation. And unless a gene benefits survival only after the ability to procreate, survival and reproduction are broadly synonymous.

Personally, I wonder whether the advantages conferred by the anti-regeneration gene has to do with conserving energy. Animals missing a limb may typically find it hard to get food, and to survive need to conserve their energy. Scarring allows the animal to return to partial functionality more quickly with less expenditur of energy. (Provided, of course, this happens during breeding years.)

[DavidDvorkin]

12. That's the advantage I was referring to, as well

I thought that was understood, but I guess I should have said it explicitly.

[txlibdem]

14. Perhaps I'm not explaining myself well at all - seemed perfectly clear to me though

Oops! My apologies.

You said, "Animals missing a limb may typically find it hard to get food, and to survive need to conserve their energy." This is exactly the point I am making but there's more to it than that. How long would it take a Human to regrow a lost leg or arm versus how long one can survive without food? Early Man could not simply conserve energy during limb regeneration: they would starve long before that. So they would need to attempt to go out and forage for food, becoming an attractive target to predators and being unable to run as fast or be unable to climb trees to escape teeth and claws, they would fall to predation.

Our genetic makeup was largely set by the time social structures, fire and weapons all developed sufficiently that a totally dependent person could be fed, cared for and (most importantly) protected from predators, without causing harm to the group as a whole.

So, regardless of age, prior to that time the severely injured or those with lost limbs would have died in short order due to predation or would have starved to death. Since the young would be naturally slower and less able to outrun predators they would be much more often targeted for predation, would be more likely to lose a limb or suffer severe injury or loss of limb, they would be even slower during regeneration -- even more greatly selecting for the activated gene. Then, too, the social group that cared for an individual so afflicted could only gather so much food themselves and caring for an unproductive member would remove food from everyone in the group so that, too, could affect the survival of the group as a whole or of their healthy offspring, thereby further selecting for the active gene.

[On the Road]

16. OK, So We're All on the Same Page Then

DavidDvorkin just seemed mystified, and I wanted to add that thought, which is turned out is what everyone else is saying already.

:toast:

[pscot]

7. Having the gene acive

may have caused too many birth defects. That could have caused it to be selected out.

[rapturedbyrobots]

9. that's not how evolution works

other strategies exist besides natural selection for the development & propagation of genes and phenotypes. just because something 'evolved' doesn't mean it was through the forces of natural selection. don't take this as a personal attack, but please learn some biology before posting this pop-sci stuff. it only serves to confuse people.

[txlibdem]

15. You are referring to random mutation?

Random mutation occurs at the egg/sperm level, thus implying that if a trait does not improve the chances of procreation then it is not selected for via evolution. There are many genetic traits that we all carry which neither help nor hinder our chances of procreation and yet are still there (what the heck does the appendix do?). But this gene, when inactive, would adversely impact a hominid's chances of living long enough to procreate. And if the social group to which the individual belonged supported him or her during regeneration the entire group would suffer. Early Man was only able to gather so much food in a day and if a good percentage of it needed to go to an unproductive member of the group that meant less for everyone else, thus it would adversely impact the entire group's chances of survival (from attack from other hominids, droughts, famine, lean times, lacking energy to escape predators, take your pick).

Or did I miss your point? Please explain the other strategies of which you spoke.

[tinrobot]

11. Could be invovled in cancer prevention.

Just pondering, but many times when cell growth is stimulated, it also increases the chances of cancer.

[Name removed]

4. Deleted message

Sub-thread removed by moderator. Click here to review the message board rules.

[JohnWxy]

13. Wow! ...the possiblities!

[qazplm]

17. talk about an extenz that really works!

vbg