Deregulated p53 signaling is responsible for the gastrulation
defect in tsg101−/− embryos. (a)
Immunohistochemical analysis of p53 protein levels. A few weakly
p53-positive cells can be detected in a wild-type E6.5 embryo (WT),
whereas strongly p53-positive nuclei occur throughout the
tsg101−/− embryo (−/−). (Bar = 50 μm.)
(b) Levels of p53, mdm2,
and p21 mRNA expression. Quantitative reverse
transcription–PCR on mRNA from individual E6.5 wild type (WT) and
mutant (−/−) embryos (see Materials and Methods).
Expression levels are calculated relative to
β-actin. p21 expression
is increased 5- to 10-fold in tsg101−/− embryos.
(c) Partial rescue of tsg101−/−
embryos by null mutation of p53. Whole mount
preparations of embryos from
tsg101+/−/p53+/− intercrosses at
E8.5. Although less advanced than their
tsg101+/−/p53−/− littermates
(Left),
tsg101−/−/p53−/− embryos at E8.5
are developing an anterior–posterior pattern with a head, trunk, and
tail region (Middle). A remnant of a
tsg101−/−/p53+/+ single mutant embryo
at E8.5 is shown on the Right. (Bar = 100 μm.)