Biomedical Engineering Reference
In-Depth Information
flanked by FRT sites, the addition of the FLP results in their deletion (as
long as the orientation of the sequences is appropriate, like the loxP
sites).
RAG-deficient blastocyst complementation
RAG-1 and RAG-2 (recombination activating
g
enes 1 and 2) are lym-
phoid specific enzymes that are required for the production of antigen-
specific receptors on T and B lymphocytes. In the absence of either
of these genes, lymphocytes do not develop. Mutations in RAG-1 or
RAG-2 are one of several defects that lead to the syndrome called
severe combined immunodeficiency (SCID). Children who are born with
this disease usually die of infections within 2 to 3 years after birth. Mu-
tant mice that lack one or the other of these genes have been created
by knockout technology. In addition to allowing for the study of the role
these enzymes play in production of lymphocytes, these mice can be
used for the creation of chimeric mice for the study of gene function in
lymphocyte development (49).
RAG-2-deficient blastocyst complementation uses blastocysts from
RAG-2 deficient mice. These are injected with modified ES cells, in which
the gene of interest has been inactivated or mutated, and implanted into
mice for development. Any lymphocytes that develop in the offspring will
have developed from the ES cells, since the RAG-2-deficient cells cannot
give rise to these lineages. Any mutations that have been introduced
in the ES cells can therefore be screened for their affect on T and B
lymphocyte development and function.
F.
Other uses of mice in biomedical research
N-ethyl-N-nitrosourea (ENU) mutagenesis
ENU is a powerful chemical mutagen that creates random single point
mutations in the genome. It is now used for genome-wide mutagenesis
studies in mice, a concept first proven to be useful for a variety of ge-
netic analysis in lower organisms, including fruit flies and nematodes.
ENU is such a powerful mutagen that it can be used to identify genes
that are involved in complex genetic traits in the mouse. ENU is used to
mutagenize spermatogonia in male mice. Once mature sperm develop
from the spermatogonia, the males are mated with untreated female
mice, and offspring are evaluated for the function in which the investiga-
tor is interested. Both dominant mutations and recessive mutations can
be detected by this methodology, although recessive mutations require
additional breeding in order to obtain animals that are homozygous for
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