Fig. 4. DLG-1 is necessary for the assembly of the CeAJ electron-dense structure. Electron microscopic analysis of CeAJs in the epidermis (A-E) and intestine (F-I) of wild-type (A,F), dlg-1(RNAi) (B,C,G,H), let-413(RNAi) (D,I) and double dlg-1(RNAi) let-413(RNAi) embryos (E). The electron-dense structure of CeAJs (arrowhead in A) was absent in most epidermal cells of dlg-1(RNAi) embryos (see text), while neighbouring cell membranes remained correctly apposed (B); where this structure was present it was slightly more elongated than in wild-type embryos (arrowhead in C). Where epidermal junctions are present in let-413(RNAi) embryos, they are discontinuous and largely extended further basally along the lateral membrane (arrowheads in D). In double dlg-1(RNAi) let-413(RNAi) embryos, the basolaterally mislocalised electron-dense junctions are no longer detectable (E). In the intestine of dlg-1(RNAi) embryo (G,H), CeAJs are also abnormal compared to wild-type (arrowheads in F) but not affected as badly as in the epidermis. In many cases, the electron-dense junctions are clearly visible (arrowhead in G) while others are absent or faint (arrows in G and H). (I) Shows a typical intestinal section in let-413(RNAi) embryos where both CeAJs are present (arrow and arrowhead), although one is elongated with respect to wild-type junctions (arrowhead). Scale bar, 300 nm.