Fig. 1. ceh-16 structure, mutants and expression pattern. (A) Exon/intron structure of ceh-16 (C13G5.1) on chromosome III. The ceh-16 gene is organized in five exons, the start methionine being in the second exon and the stop codon in the fifth exon. Structure of the deletion mutants. Bottom: structure of translational gfp fusion constructs used in this study. In both constructs ceh-16 expression is driven by the endogenous promoter region and contain the unc-54 3' UTR of the plasmid pPD95.75. The construct on top rescued the ceh-16 phenotype mutant. (B) Amino acid sequence of the proposed ceh-16 gene product (187 aa), underlined: epitope for Mab 4D9 (Patel et al., 1989). (C,D) Expression pattern of the rescuing gfp construct is most robust from 250 minutes after the first cleavage (C) throughout embryonic development (D) (1.5-fold stage of elongation) until early 3-fold stage (not shown). Expression was observed in the nuclei of hyp5, H0-H2, V1-V6, T. Some of these cells are not in the focal plane of the pictures. (E,F) Antibody staining of embryos at the same developmental stages as shown in C,D. All nuclei that expressed ceh-16::gfp were also stained with the monoclonal antibody 4D9 (Patel et al., 1989). (G,H) Schematic representation of the position of ceh-16 expressing cells [based on Sulston et al. (Sulston et al., 1983)]. Scale bar: 10 µm.