“Cell polarity and aging – a unifying theory”

Continuing with the theme of unifying theories in aging: Over at The Daily Transcript, Alex Palazzo has written up a thoughtful and detailed analysis of a recent review (the original paper is entitled Polarity and Differential Inheritance: Universal Attributes of Life?). In his post, he also introduces some fantastic new nomenclature (emphasis in the original).

Let’s pretend you are a unicellular organism – what would be the best strategy to ensure the long-term multi-generational survival of your lineage?

One approach is to distribute everything equally amongst your two offspring. …

A second approach is to give all the crap to one of the two new cells and keep the other one pristine. Lets call these two cells the crap cell and the pristine cell. What’s the result of this second strategy? Using our crap metric from above, the first cell accumulates 10 units of garbage over its lifetime and then gives it all to one offspring, the crap cell, and none to the other offspring, the pristine cell. Those cells then grow and by the time they divide each second generation cells have made 10 units of additional crap each. The crap cell has 20 units the pristine cell 10. The two cells divide and dump all their garbage on one of their offsprings. One cell starts with 20 units of crap, one cell with 10 units and two cells are again crap free. The end result of this strategy? Part of your descendents will become more and more decrepit as they fill up with crap, while others remain pristine.

Somewhat reminiscent of the garbage catastrophe, but with important differences — and this time with evolutionary legs.

Alex has teased us with the suggestion that this will be the first of multiple parts to his coverage of this issue. If so, that’s exciting news; he has done some excellent multi-part stories in the past (e.g. these posts on cancer and metabolism). I’m looking forward to the next chapter.



  1. Could it be possible for your old cells to pinch off all their old cellular machinery (how would you get rid of the old cell?) and generate new pristine cell parts?

  2. Isn’t this what yeast cells do? The daughter cells get the good stuff, and the mother cell keeps the crap, until it stops reproducing. If good and bad were divided equally, all yeast cells in the world would die at the same time and yeast would go extinct.

  3. I’m not sure whether this suggestion is naive or not, but there are two papers which identify molecular “clocks” that count how many mitoses have taken a cell to its current phenotypic niche:
    “Estimating Cell Depth from Somatic Mutations”
    “Counting human somatic cell replications:
    Methylation mirrors endometrial stem cell divisions”
    Would a good test of the theory be to correlate the amount of damaged proteins, etc., in a cell with its mitotic counter?

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