Worm Breeder's Gazette 12(2): 105 (January 1, 1992)

These abstracts should not be cited in bibliographies. Material contained herein should be treated as personal communication and should be cited as such only with the consent of the author.

Looking for Glycosylation Mutants

Chris Link, Michelle Enyeart

Dept. of Biology, Univ. of Denver, Denver CO 80208

Although we have generated a large collection of mutants (designated srf) that have novel surface lectin-binding properties, it is not clear if any of these mutants have intrinsic changes in glycosylation. Surface radio-labeling and lectin blot experiments suggest that these mutants bind lectins not because they have novel glycoproteins, but because normally cuticle-internal glycoproteins are being "unmasked". We have devised a screen to more directly identify glycosylation mutants by looking for extragenic suppressors of srf mutants. Suppressor mutations could theoretically block srf mutant lectin binding by removing, modifying, or masking the relevant cuticle glycoprotein(s). Among these suppressors should be mutants that fail to bind lectins because of changes in the carbohydrate component of the relevant cuticle glycoprotein.

srf-5 ( ct115 )animals show highly penetrant ectopic surface binding of the lectins SBA and WGA, but are otherwise wild-type in morphology and behavior. We screened the progeny of EMS-mutagenized srf-5 animals for variants that did not bind the lectin SBA using a modification of our original biotinylated lectin/ avidinHRP protocol, and identified 9 independent suppressor mutations. These mutations define at least 4 complementation groups. Although we have not yet biochemically characterized these mutants, it is interesting to note that 3 of the 9 suppressors still show ectopic binding of WGA. This phenotype would be expected for mutations that block the addition of N-acetyl galactosamine (recognized by SBA) but not N-acetyl glucosamine (recognized by WGA) to glycoproteins.

Because we are strongly biased in believing that C. elegans does not glycosylate proteins so the Link lab can find lectin-binding mutants, our hope is that if we do identify glycosylation mutants, they will have other phenotypes that will give us insights into the biological role of glycosylation. We are therefore encouraged that 4 of our original isolates also show an Unc phenotype.