Ak. Hadjantonakis et al., GENERATING GREEN FLUORESCENT MICE BY GERMLINE TRANSMISSION OF GREEN FLUORESCENT ES CELLS, Mechanisms of development, 76(1-2), 1998, pp. 79-90
Green fluorescent protein (GFP) and its variants currently represent t
he only non-invasive markers available for labeling mammalian cells in
culture or in a multicellular organism through transgenesis. To date
this marker gene has been widely used in the study of many organisms,
but as yet has not found large-scale application in mammals due to pro
blems encountered with weak fluorescence and instability of the wild-t
ype protein at higher temperatures. Recently, though, several mutants
have been made in the wild-type (wt) GFP so as to improve its thermost
ability and fluorescence. EGFP (enhanced GFP) is one such wtGFP varian
t. As a first step in assessing the use of EGFP in ES cell-mediated st
rategies, we have established a mouse embryonic stem (ES) cell lines e
xpressing EGFP, which can be propagated in culture, reintroduced into
mice, or induced to differentiate in vitro, while still maintaining ub
iquitous EGFP expression. From the results presented we can suggest th
at: (1) possible improvements in the efficiency of transgenic regimes
requiring the germline transmission of ES cells by aggregation chimera
s can be made by the preselection chimeric embryos at the blastocyst s
tage; (2) the expression of a noninvasive marker, driven by a promoter
that is active during early postimplantation development, allows acce
ss to embryos during a window of embryonic development that has previo
usly been difficult to investigate; (3) the behavior of mutant ES cell
s can be followed with simple microscopic observation of chimeric embr
yos or adult animals comprising green fluorescent cells/tissues; and (
4) intercrosses of Fl mice and subsequent generations of animals show
that progeny can be genotyped by UV light, such that mice homozygous f
or the transgene can be distinguished from hemizygotes due to their in
creased fluorescence. (C) 1998 Elsevier Science Ireland Ltd. All right
s reserved.