Fig. 3. Compartment boundaries in the peripodial epithelium. (A-C) Expression of en-lacZ in the wing PE and DP during larval development. (A) 55 hours; (B) 72 hours; (C) 110 hours AED. An anterior shift of en-expression in the PE relative to the en-expression in the DP coincides with the formation of squamous PE cells. Scale bar in A: 50 µm (A-F,M-O). (D-F) The en-expression domain in the wing PE defines a clonal restriction. (D) A GFP-expressing PE cell clone straddles (arrowhead) but does not cross the en-expression domain (F) in the PE. (E) Overlay of D and F. (G-I) Large M⁺ PE cell clones respect the AP compartment boundary in the wing PE. (G) A +/+ PE cell clone, generated in a Minute mutant background, is distinguished by two copies of GFP (outlined in red) and grows along but does not cross the anterior Ci expression domain in the PE (arrowhead) in I. (H) Overlay of G and I. (J-L) PE cells in the wing disc belong to the V compartment. (J) Random GFP-expressing PE clones grow adjacent to without crossing the ap-lacZ expression domains (L) in the wing PE or DP. (L) ap-lacZ expression (red asterisk) is limited to 40+ margin cells in the P compartment of the PE. (K) Overlay of J and L. (J'-L') Enlargements of the boxed region in K. (J') A PE cell clone (outlined in red) that grows next to but does not cross the ap-lacZ (asterisk in L') expression region in the PE (L'). (K') Overlay of J' and L'. A yellow line marks the DV compartment boundary in the DP (lower layer), asterisk indicates ap-lacZ in PE. .The PE cell clone in J-L' traverses the DV compartment in the DP. Scale bars: 50 µm. (M-O) M⁺ cell clone in the eye PE reveals that the Bolwig's nerve defines a DV lineage restriction. (M) Heterozygous M/+ cells are marked by Arm-lacZ. A +/+ PE cell clone is distinguished by the absence of Arm-lacZ (M) and two copies of GFP (O) and defines a straight line left of the Bolwig's nerve (arrowheads and outlined in red). (N) Overlay of M and O.