The adult cuticle of the soil nematode, Caenorhabditis elegans, is a proteinaceous extracellular structure elaborated by the underlying layer of hypodermal cells during the final molt in the animal's life cycle . The cuticle is composed of an outer cortical layer connected by regularly arranged struts to an inner basal layer. The cuticle can be isolated largely intact and free of all cellular material by sonication and treatment with 1% sodium dodecyl sulfate (SDS) . Purified cuticles exhibit a negative birefringence due to ordered material in the basal cuticle layer . The cuticle layers differ in their solubility in sulfhydryl reducing agents, susceptibility to various proteolytic enzymes and amino acid composition. The struts, basal layer, and internal cortical layer are composed of collagen proteins that are extensively cross-linked by disulfide bonds . The external cortical layer appears to contain primarily noncollagen proteins that are extensively cross-linked by nonreducible covalent bonds . The collagen proteins extracted from the cuticle with a reducing agent can be separated by SDS-polyacrylamide gel electrophoresis into eight major species differing in apparent molecular weight.

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We have analyzed a set of linkage group (LG) II maternal-effect lethal mutations in Caenorhabditis elegans isolated by a new screening procedure. Screens of 12,455 F1 progeny from mutagenized adults resulted in the recovery of 54 maternal-effect lethal mutations identifying 29 genes. Of the 54 mutations, 39 are strict maternal-effect mutations defining 17 genes. These 17 genes fall into two classes distinguished by frequency of mutation to strict maternal-effect lethality. The smaller class, comprised of four genes, mutated to strict maternal-effect lethality at a frequency close to 5 X 10(-4), a rate typical of essential genes in C. elegans. Two of these genes are expressed during oogenesis and required exclusively for embryogenesis (pure maternal genes), one appears to be required specifically for meiosis, and the fourth has a more complex pattern of expression. The other 13 genes were represented by only one or two strict maternal alleles each. Two of these are identical genes previously identified by nonmaternal embryonic lethal mutations. We interpret our results to mean that although many C. elegans genes can mutate to strict maternal-effect lethality, most genes mutate to that phenotype rarely. Pure maternal genes, however, are among a smaller class of genes that mutate to maternal-effect lethality at typical rates. If our interpretation is correct, we are near saturation for pure maternal genes in the region of LG II balanced by mnC1. We conclude that the number of pure maternal genes in C. elegans is small, being probably not much higher than 12.

Eighty-eight mutants of C. elegans that display a roller phenotype (a helically twisted body) have been isolated and characterized genetically and phenotypically. The mutations are located in 14 different genes. Most genes contain a number of alleles. Their distribution among the chromosomes appears nonrandom, with seven of the genes being located on linkage group 11, some very closely linked. The phenotypes of the mutants suggest that there are five different classes of genes, each class representing a set of similar phenotypic effects: Left Roller (four genes), Right Roller (one gene), Left Squat (one gene), Right Squat (two genes) and Left Dumpy Roller (six genes). The classes of mutants differ with respect to a number of characteristics that include the developmental stages affected and the types of aberrations observed in cuticle structure. A variety of gene interactions were found, arguing that these genes are involved in a common developmental process. The presence of alterations in cuticle morphology strongly suggests that these genes are active in the formation of the nematode cuticle.