Fig. S1

Characterization of baos^s866 Mutant Phenotype (Related to Figures 1 and 3)

(A) baos^s866 mutant enterocytes retain absorptive cell marker expression and localization. 120 hpf WT and baos^s866 mutant larvae were fixed in PFA, sectioned and stained for the absorptive marker 4e8. In baos^s866 mutant enterocytes, 4e8 (green) was expressed and localized apically as in WT. The arrow points to the apical membrane. Scale bars represent 50 μm.

(B) Delaminating cells in baos^s866 mutants undergo apoptosis. 120 hpf WT and baos^s866 mutant larvae were fixed in PFA, mounted, sectioned and subjected to the Tunel assay to detect apoptotic cells. While all delaminating cells in baos^s866 mutant larvae were Tunel positive (red channel, arrows), the proportion of gut cells undergoing apoptosis in WT and baos^s866 mutant larvae were essentially the same. Scale bars represent 25 μm.

(C) Exocrine pancreas degeneration and liver growth arrest in baos^s866 mutant larvae. To visualize endodermal organs, we crossed the baos^s866 mutation to a transgenic line expressing GFP and DsRed in the exocrine pancreas and liver, respectively. baos^s866 mutant larvae showed a fully penetrant (~100%) exocrine pancreas phenotype (arrows) at 120 hpf. We also detected a variable degree of liver growth arrest (arrowheads) compared to WT siblings. In contrast, we did not detect any obvious pancreatic islet defects (not shown). These phenotypes are fully consistent with cse1l’s expression pattern (see Figure 3F).