Figure 3

Elongation of the arm. (A to D) Confocal projections of surface epithelium stained with phallacidin to visualize F-actin, aboral view, proximal to left. Arrows and dotted lines (D) point into the direction of cell elongation. (E) to (H) arm crown (E) and close-up (F) to (H) of control embryo. (I) to (L) and (M) to (P) embryos treated with 1 or 5 μM CytD. (E, I, M) embryos stage 23 stained with phallacidin (green) and Hoechst to visualize nuclei (red), lateral view, anterior to the left. Asterisks indicate position of mouth. (F, J, N) Sagittal confocal sections of arm buds corresponding to embryos in (E, I, M), proximal to left. Arrows point at basement membrane. (G, K, L) Confocal stacks of arm buds in (F, J, N) showing the surface epithelium, oral view. Dotted line in (O) indicates outer margin of arm bud. Boxed regions are magnified in (H, L, P). Row (Q) to (S) control embryo (Q) and arm at stage 25 (R to S). Row (T) to (V) embryo treated with 1 μM CytD until stage 23, washed and left to develop until stage 25 (T) and arm at stage 25 (U to V). (Q, T) embryos stage 25 stained with phallacidin (green) and Hoechst (red), lateral view, anterior to the left. (R, U) Confocal stacks of arm buds in (Q, T) and surface epithelium of the same arms stained with phallacidin (S, V), oral median view. Numbers in the right lower corner in (I, M, T) shows number of embryos with this phenotype in relation to number of embryos treated. Abbreviations: e, eye; ep, epithelium. Scale bars: E (refers to E, I M), Q (refers to Q, T): 300 μm; A (refers to A to D), F (refers to F, J, N), G (refers to G, K, O), H (refers to H, L, P), R (refers to R, S and U, V): 100 μm.