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Scotty Wilcoxen scwilcox at pacbell.net
Wed Jan 14 23:54:55 EST 1998

Dear Shayne,
    Hi there.  In response to your inquisitive question regarding vectors,
what you are suggesting is quite a feat.  Realize that every cell in the
body maintains the full genome of that individual.  In order to knock out
that gene, you would need to in effect knock out the gene in any cell type
that is associated with the given disease.  As a minor point though, vectors
themselves do not alleviate any problems.  All a vector does is act as a
delivery mechanisms to import any exogenous substance, gene, or otherwise
into the cell in question.  Vectors contain many different things.  I am a
PhD student in a Gene Therapy lab where I work on vectors.  My vector of
choice is the retrovirus.  What we do is use the retrovirus backbone as a
means of delivery genes to cells.  Viruses contain promoters and enhancers,
just as your DNA does to increase the expression of genes.  Many promoters
are tissue specific also.  Infact, that is a main focus point in vector
work, trying to obtain promoters and enhancers that will express the given
gene only in B cells, or only in Embyronic Stem cells.  So yes, you can
achieve effective tissue specificity.  But we combat the problem in a
different manner.  We identify the problem caused by the mutation, then try
to supply progenitor cells with functional copies of the mutant gene.  This
way the progenitor cells can hopefully repopulate many different cell types
with the corrected gene.  Going in and trying to knock out the bad gene
would in effect cause the same problem as the mutation in many ways.  Many
diseases are caused by a mutation that results in a non-functional protein.
Taking away that gene would only further the absence of the needed enzyme or
protein.  Anyway, I'll stop rambling.  If you want more info, feel free to
drop me a line.  In the mean time, keep asking good questions.
Scotty Wilcoxen
wilcoxen at hsc.usc.edu
University of Southern California
School of Medicine
Molecular Microbiology and Immunology

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