"CNS specific knock-outs for cre-lox"

Neurobiol at aol.com Neurobiol at aol.com
Thu Sep 26 18:14:10 EST 1996

un691cs at genius.embnet.dkfz-heidelberg.de (z)  started this subject by writing

>> here in the lab we would like to make CNS specific knock-outs
>> with the cre-lox system. For this, I am looking for a CNS (not
 >> PNS !) specific promoter, which is either expressed only in CNS
>> neurons, or in CNS neurons as well as glia. neurofilament, 14-3-3,
>> vimentin, nestin or negrin won't do, as these are either 
>> expressed in PNS neurons or outside by non-neural cells as well.
>Reply From: mhulsey at fcs.uga.edu (Martin G. Hulsey)

>Take a look at Retina-derived POU-domain factor-1 (J. Neurosci. 16(7):
>2261-2274;1996) or Na+/Cl(-)-dependent "orphan" transporter Rxt1  (J.
>Neurosci. Res. 42(3): 423-432; 1995.
>As an aside, do you think that CNS-relevant knockout models are >useful to
>learn about the role of gene products in normal animals (aside from a >role
>in neuronal development, perhaps)?  The recent NPY knockout has me
>thinking otherwise, because the results were so discordant compared to
>exogenously-administered peptide.
>I would submit that temporal control of cre or flp expression will prove
>to be as important as neuroanatomical control, if not more so.  This is
>because it is now apparent that neural networks can develop in >alternative
>ways that can compensate for the total absence of an otherwise >important
>gene product like NPY.

First, I believe there was a report at the mouse meeting of a cre-lox
knockout made by crossing a cre transgene driven by the nestin promoter into
a strain that was knocked out for something (I forget what ) that is lethal
in embryogenesis when homozygous.  I've been too lazy to look up the
expression pattern of nestin, but I gather from your comments that the PNS
should have been affected, too.  Does anyone have a better knowledge of this
work?  I wasn't at the meeting and heard it secondhand...
Second, Martin, I agree with you that it is very nice but not sufficient to
restrict the knockout to a particular cell type by breeding to a tissue
specific promoter-cre mouse line.  I have a couple of reservations.  The
first is practical.  Not a lot of promoters are really tissue specific, and
it doesn't take much cre expression to irrevokably alter a cell that might be
the first in a lineage of any organ.  I suspect there will be a few
undiagnosed chimeras caused by this method if people don't look at the
animals thoroughly.   The second reason I think that the cre needs to be
delivered temporally is of course the issue you bring up-  that delivery of a
knockout to a specific cell type- by retrovirus? naked DNA? liposomes?- is
the next step, AFTER the simple knockout is replaced with the
tissue-restricted knockout.
Interesting stuff.  I'd like to continue this discussion.  Anyone else?
Jeanne Loring
jloring at mdyn.com 

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