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Fig. 6. In vivo regulation of Serrate and Delta localization and stability by
D-mib. In all discs excepting E and F, Delta is in red and Serrate in green.
(A-D) Tests of endogenous D-mib function. Wing imaginal discs from wild-type
(A,C) and D-mib1 (B,D). Apart from the defective wing
pouch development, Dl expression is fairly normal in D-mib discs (B),
but elevated levels of Serrate are present and localized primarily to the
plasma membrane (D). Imaging of Delta and Serrate in A-D was performed
identically, so that relative protein levels between discs is comparable.
(E-P) Tests of ectopic D-mib function. In these experiments, D-mib isoforms
are expressed in a stripe at the anteroposterior compartment boundary using
dpp-Gal4. (E,F) dpp-Gal4, UAS-nGFP double stained for GFP
(E) and GFP + Delta (F). The L3 wing vein expression of Delta is contained
within the domain of dpp-Gal4 activity. (G-L) Wing discs double
stained for Serrate and Delta. In all cases, the L3 wing vein domain is marked
with an asterisk, and insets depict magnified apical views from this region.
(G,H) Wild type. (I,J) dpp-Gal4, UAS-D-mib discs show a reduction of
Serrate from the apical membrane and a strong decrease in both the apical and
total level of Delta. (K,L) dpp-Gal4, UAS-D-mib
RF
disc displays strongly increased levels of both Serrate and Delta. Endogenous
margin-specific expression of Serrate and Delta is also interrupted
(arrowhead). Note the large apical intracellular aggregates of Serrate (K,
inset). (M-P) Effect of D-mib proteins on exogenous Delta. In these panels,
one copy of hs-Delta is present, and animals were heat-shocked at
38°C for 40 minutes, then allowed to rest for the indicated period of time
prior to dissection and fixation. The regions shown in (N-P) correspond to the
boxed region in F. (M) hs-Delta/+, 40 minute rest. Delta is present
at the plasma membrane of all cells. (N) hs-Delta, dpp-Gal4,
UAS-D-mib, 40 minute rest. All Delta within the D-mib-expressing domain
is vesicular. (O) hs-Delta, dpp-Gal4, UAS-D-mib, 90 minute rest. All
Delta within the D-mib-expressing domain has been degraded. (P) hs-Delta,
dpp-Gal4, UAS-D-mib
RF, 120 minute rest. D-mib
RF
fails to efficiently induce either the internalization or degradation of
Delta.