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?
In many cases, the transgene will continue to be expressed even without
continued selection. However, in others (and as far as I know it's
unpredictable) the transgene will lose expression over some number of
passages if you don't keep selecting. Presumably in those cases the
transgene is moderately deleterious (whether in itself, due to high level
expression, or due to its site of integration) and the continuous
background of mutation going on in the cells allows some deletion mutants
to arise and outgrow the transgene-containing majority.
For any particular case, it's probably worth keeping cells in no selection
or with only intermittent selection and seeing how the trangene behaves,
but you'd want to make sure there were early-passage clones available in
case you lose your gene.
Ian York (iayork at panix.com) <http://www.panix.com/~iayork/>
"-but as he was a York, I am rather inclined to suppose him a
very respectable Man." -Jane Austen, The History of England