Lectin-resistant CHO cells: Selection of seven new mutants resistant to ricin

In attempts to isolate new CHO glycosylation mutants, selection protocols using plant lectins that bind galactose residues of cell surface carbohydrates were applied to mutagenized CHO populations. The lectins were used alone or in combination to obtain seven ricin-resistant phenotypes. Each mutant had distinctive properties compared with previously described ricin-resistant CHO cells. One of the new phenotypes was dominant in somatic cell hybrids, and the others were recessive. Complementation analyses between related lectinresistant (Lec^R) phenotypes indicated that each new isolate represented a novel genotype. Five of the mutants had properties typical of new CHO glycosylation mutants. The remaining two mutants were not readily categorized. Although they did not appear to be ricin-internalization or protein-synthesis mutants, they also did not display the marked alterations in sensitivity to several lectins of different sugar specificity expected for glycosylation mutants. The seven new Lec^R mutants described in these studies brings the total number of different Lec^R CHO mutants isolated by this and other laboratories to about 40. Criteria for identifying new Lec^R mutations in CHO cells are discussed.