Immunocytochemical and freeze-fracture characterization of the Caenorhabditis elegans DR 847 bli-1(n361) mutant which produces abnormal cuticle blisters

The bli-1 gene of Caenorhabditis elegans has previously been described as a mutation which disrupts the structure of the adult-stage cuticle, causing the formation of fluid-filled blisters. We investigated the blistering phenotype exhibited of n361 allele through immunocytochemical and freeze-fracture techniques. In the course of the blistering process several fine changes occurred, including a high-electron-density granulous material filling the intermediate layer, alterations in strut structure, and finally the total disappearance of the fibrous and basal layers. A polyclonal antibody against a synthetic 18-amino-acid peptide of the 3A3-collagen sequence labeled all the cuticular regions of the N(2) strain of the nematode C. elegans except for the intermediate layer. Similarly, no reaction was observed in the intermediate layer of the mutant strain DR 847 bli-1 (n361), which was filled by the granulous and electron-dense material. Replicas of quick-frozen, freeze-fracture, deep-etched, and rotatory-shadowed adult forms of the mutant DR 847 bli-1 (n361) of C. elegans revealed an increased number of the filamentous structures filling the intermediate layer in older nematodes, and also a gradual destruction and disappearance of the fibrous and basal layers. Based on these results, we postulated that the blistering phenotype is due to an altered function of bli-1 gene, which is probably enzymatic.