The
unc-82 gene was identified by screening for disorganized body-wall muscle cells in mutagenized adults. The
unc-82 gene encodes a serine/threonine kinase that is required for proper organization of thick filaments and membrane-distal components of the M-line (Waterston et al., 1980; Chau at al., submitted). In addition to moving more slowly than wild type,
unc-82 mutants have decreased pharyngeal pumping and an incompletely penetrant Egl phenotype. A rescuing UNC-82::GFP fusion revealed that UNC-82 is expressed in the pharynx and vulva, as well as in body-wall muscles. Pharyngeal muscles are attached to the cuticle-covered lumen on one side and to the basement membrane surrounding the pharynx organ on the other. TEM of mutant adult pharynges revealed detachment of pharyngeal muscle and marginal cells from the cuticle lining the buccal cavity; attachments to the basement membrane surrounding the organ were unaffected. UNC-82::GFP is found near the pharyngeal muscle-to-cuticle attachment structures, which contain intermediate filaments, Vab10a/plectin and MUP-4. Unlike body-wall muscle staining, UNC-82::GFP is not detected near thick filaments in the pharynx. The muscle detachment in the pharynx suggested that the Egl phenotype might result from detachment of the egg-laying muscles. However, light microscopy and TEM analyses showed that vulva muscles remained attached to the vulval epithelium. Instead, the Egl phenotype is likely due to defects in the epithelial cells of the vulva, which appear damaged in
unc-82 mutants. Attachment proteins such as MUP-4 and the intermediate filament MUA-6, are disorganized compared to wild type. Preliminary TEM suggests that the vulval cells detach from the exterior cuticle. The similarity of the cell attachment defects in the vulva and pharynx suggest that UNC-82 is involved in regulation of attachments in these tissues. The pharynx and vulva cells affected contain similar molecular components in their attachment structures, which mediate direct attachment of the cells to the cuticle which they themselves secrete. Our model is that
unc-82 regulates proper organization of cell attachment structures at the cuticle-to-membrane interface in the pharynx and vulva.