Fig. 4. path is broadly expressed during development and affects global and local growth signals. (A-C) In situ hybridisation with a path antisense probe reveals expression in almost all tissues during embryonic development, including stages 11 (A), 13 (B) and 16 (C). High transcript levels were observed in specific tissues, such as the muscle primordia (white arrowhead), midgut (white arrow), proventriculus (black arrowhead) and salivary glands (black arrow). A path sense probe gave no signal (data not shown). In path^KG06640 homozygous embryos (D), a signal was observed only after extended staining times. (E-H) In situ hybridisation of wing (E,F) and eye antennal (G,H) imaginal discs from wild-type (E,G) and path^KG06640 homozygous (F,H; overstained to detect signal) climbing third instar larvae. path is normally most strongly expressed in the pouch (arrow) and hinge (arrowhead) regions of the developing wing and at the morphogenetic furrow (arrowhead) in the eye. (I-K) Eyes that are almost entirely generated from homozygous path^KG06640 cells via the eyFLP/FRT cell lethal method (J) were very similar in size to eyes of normal flies (I), and not small like those of path^KG06640 homozygotes (K). (L-N) Dorsal views of eyes almost entirely generated from Tsc2 mutant cells (M) and Tsc2 path^KG06640 double mutant cells (N) were compared with normal controls (L). Fly genotypes are: y w eyFLP/w; path^KG06640 FRT80B/rps17⁴ P[w⁺] FRT80B (J); y w eyFLP/w; Tsc2¹⁹² FRT80B/rps17⁴ P[w⁺] FRT80B (M); and y w eyFLP/w; path^KG06640 Tsc2¹⁹² FRT80B/rps17⁴ P[w⁺] FRT80B (N).