Fig. 2. Founders and fusion-competent myoblasts are determined in kette-null mutants. kette mutants were analysed for expression of the enhancer trap rP298-lacZ (A-D) and localisation of the sns-transcript (E,F) to examine the determination of founders and fusion-competent myoblasts. (A-D) Expression pattern of the rP298-lacZ enhancer trap (green), which resembles the founder cell marker duf/kirre expression pattern, shown by anti ß-galactosidase fluorescent staining. ß3-Tubulin fluorescent staining is red. (A) Stage 13 heterozygous wild-type embryo with TDLZ blue-balancer. (B) Stage 13 kette^J4-48-null mutant. (C) Late stage 13 wild-type embryos. After fusion, all nuclei of the syncytia express rP298. The forming dorsal muscles contain more than four nuclei and muscle structures is visible. (D) In stage 13 kette^J4-48-null mutants, founder cells are determined but no muscle structure are visible. Compared with wild type, less rP298-positive cells are detected that are surrounded by many fusion-competent ß3-Tubulin-positive myoblasts (arrow). (E,F) Fluorescence in situ hybridisation with sns-antisense probe shows the correct determination of fusion-competent myoblasts in the somatic (sm) and visceral mesoderm (vm) of kette mutants. (E) Stage 11 wild-type embryo; (F) stage 11 kette^J4-48-null mutant embryo.