why G418 with stable lines?

[John Watson]

Ian A. York wrote:
> 
> In article <01bbbfd6$9e62c400$21746a8d at meb_493a.cvrc.mcw.edu>,
> Joe Miano <jmiano at post.its.mcw.edu> wrote:
> >
> >If a transgene is stably integrated in a cell line through selection with
> >G418, why is continued G418 necessary with clonally-derived cells?  It
> >seems that once the gene is integrated and cloned, no further G418 would be
> >necessary, n'est ce pas?

<stuff snipped to allow Netscape to post reply>

In all the stable transfectants I've ever tested, the transgene was notoriously 
unstable.  FWIW, here's my take on what's going on.  Standard production of stable 
transfectants involves illegitimate recombination to insert the transgene into the 
recipient genome.  There is probably some reason to think that this event will 
occur more readily in an "unstable" region of the genome.  DNA slides in, DNA 
slides out.  If there's no selection pressure, your homogenous population of 
transfected cells quickly becomes heterogeneous, with the end result that the 
cells still carrying the transgene after however many generations sans selection 
become diluted out.

Just my 0.02.
----------------
John Watson
Bristol-Myers Squibb Co.
watson_j at bms.com
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