Figure 6.

Tissue-specific inhibition of gene expression. (A) Schematic representation of experimental design and (B) single confocal sections of anterior part of intestine in L4 larvae. The endogenous baf-1 locus was modified by insertion of a GFP KO cassette immediately upstream of the coding region. The GFP KO cassette contains Frt sites in the first and second intron [indicated as g > f > p in (B)]: these sites do not interfere with pre-mRNA splicing and, in the absence of FLP, the locus expresses GFP::BAF-1. In cells expressing FLP, GFP exon 2 is excised and the spliced mRNA contains a premature termination codon (red TAA), which triggers nonsense-mediated mRNA decay. (B) The left animal expresses GFP::BAF-1 in all cells, whereas the right animal lack expression in intestinal cells due to the specific expression of FLP in this tissue. Nuclei of different tissues are indicated: ph: pharynx; int: intestine; bwm: body wall muscle nuclei; germ: germ line. An asterisk indicates an enlarged intestinal lumen surrounded by abnormally thin cellular processes. Bar, 10 µm. Chr, chromosome; KO, knockout.