In article <3lodlg$5hp at mserv1.dl.ac.uk>, <W.G.VAN.DOORN at ATO.AGRO.NL> wrote:
> The next question is how old do individual cells really get. I would like
> to ask for sound proof, derived from individually tagged cells, showing
> their age. Andy thinks that the stem cells in the intestine live as long
> as the individual human being. If this is true the maximum age of an
> individual cell is at least 120 years. Can anyone add to this list, but
> please only when also quoting the paper in which it has been
> published. For me the list has not yet started, as I would like to know
> whether the intestine stem cells live that long for a fact.
This experiment is undoable, or needs redefining. The only part of a cell
that is truly immortal is the DNA sequence - you could tag the DNA of a
stem cell at birth and see if the tag is still there at age 120. If it is,
it will be in a cell derived from the tagged cell - and you will be able
to conclude that the lineage is continuous and so that the first cell was
immortal (The rest of the cell (the proteins, the membranes etc. etc.) is
long turned over. Of course the atoms in the DNA as well - just the
sequence will be the same.)
But to me that is no different from saying that the stem cell that divides
at age 120 is immortal because by definition it is derived from a cell
that was onboard at birth. You only get cells from other cells - they are
not ever made de novo. So the experiment would be to see whether there are
any dividing stem cells at age 120 - and that is all. Its immortality, by
the way, does not mean that it will not produce daughters that are mortal.
Oh by the way - could we all post to the group, please - it is a bit like
listening to one side of a phone conversation right now.
Oliver
