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Fig. 4. Hh moves from cell to cell. All the wing discs were derived from third
instar larvae. Anterior is towards left and dorsal is upwards in all the wing
disc images (A-H). (A-C') dpp-lacZ staining (red) in a
wild-type wing disc (A), and discs carrying sfl9B4 mutant
clones (B,B',C,C'). In the wild-type wing disc, dpp-lacZ
is expressed in eight to ten cells anterior to the AP boundary in response to
Hh signal (A). dpp-lacZ expression was only observed in a maximum of
three cells at the posterior edge of sfl9B4 clones (marked
by broken lines in B and C, and by the absence of GFP in B' and
C'), and high levels of lacZ expression were only detected in
one or two cells adjacent to posterior wild-type cells. (D-H) GFP-Dpp
expression under the control of dppGal4 in a wild-type
wing disc (D) and discs carrying mutant clones of sfl9B4
(E,F), ttv63 (G), and
dally80-dlyA187 (H). The mutant clones
are marked by the absence of
Myc (E,F,H) or ß-gal (G) staining (red)
and are outlined with broken lines. In all cases, GFP-Dpp expression is
restricted to the posterior-most row of cells in the mutant clones. Hh
movement towards anterior cells is blocked by even one cell diameter of mutant
clones (arrows in B,C,E,H) as indicated by dpp-lacZ or GFP-Dpp
expression.