Fig. 4. ceh-16 regulates early seam cell markers. (A,C,E) Wild-type expression by means of integrated gfp constructs [elt-5 (Koh and Rothman, 2001)] or extrachromosomal arrays [nhr-73 and nhr-74 (Miyabayashi et al., 1999)]. (B,D,F) corresponding Nomarski micrographs. (G-L) Corresponding gfp strains in which ceh-16 was knocked down by ceh-16(RNAi). (K,L) Dorsal view. All the markers were downregulated and all animals show the phenotypic hallmarks of ceh-16(—), although to a lesser extent due to lower penetrance in RNAi experiments (Table 1). (M-P) ceh-16 ectopically induces elt-5::gfp expression. Ectopic expression of ceh-16 is achieved by a heatshock-inducible promoter (see Materials and methods). (M) Effects of ceh-16 misexpression in the epidermis; upper arrow points to irregularities at the tip of the tail, which are reminiscent of failed fusion events [similar as in eff-1 mutants (Mohler et al., 2002)]. (N) Ectopic expression of elt-5::gfp (arrows). (O) Similar to M (upper rightmost arrow points to the anus). (P) Lower arrow (also entire lower margin of the larva) points to ectopic dorsal expression of elt-5::gfp. Scale bars: 10 µm for all embryos; 20 µm for all L1 larvae.