Nematode's cuticles are mostly made of collagen like proteins; there are however non collagenous components of this structure. From the cuticles of all stages of all nematodes a collagenase resistant residue can be prepared. This residue is insoluble in SDS, urea or mercaptoethanol. Its amino acid composition has been determined for Ascaris cuticles and differs from that of collagen; its structure has been studied by light and electron microscopy in C. elegans. Cuticlin was the name originally given to this residue. We have cloned two C. elegans genes coding for components of this residue, and we have named them cut-l and
cut-2. The complete nucleotide sequences of these genes and their mRNA will be presented; cut-l mRNA is 1422 nt long, has four exons coding for 423 amino acids and is transpliced to SLl;
cut-2 mRNA is 847 nt long, contains only two exons coding for 237 amino acids and is not transpliced. The transcription pattern of both genes will also be presented. One of the genes, cut-l, is transcribed at high rate during dauer formation, while
cut2 seems to be present in RNA from different stages and is particularly abundant in RNA from late developing embryos. Parts of both genes have been expressed as fusion proteins in E. coli and have been used to raise specific antibodies. We have used these to identify the products of cut-l and
cut-2 in western blots of extracts of C. elegans. By immunofluorescence on worms at different stages we have shown that the product of cut-l is part of the dauer cuticle. Data on the determination by immuno electron microscopy of the layers of the cuticle to which cut-l and
cut-2 contribute will also be presented. The deduced amino acid sequences of the two genes will be compared with that of proteins that partecipate in the formation of the cuticle of the insect Locusta migratoria to which especially
cut-2 shows some meaningful homology. Possible biochemical mechanisms that make these proteins insoluble once assembled in the cuticle will be discussed. Poster