A carbohydrate epitope expressed uniquely on the cell surface of Drosophila neurons is altered in the mutant nac (neurally altered carbohydrate).

Antibodies against horseradish peroxidase (anti‐HRP) recognize neural specific cell surface antigens in Drosophila and other insects. The nature of these antigens was investigated in Drosophila and found to include a complex set of developmentally regulated proteins. Their common epitope appears to be a carbohydrate that shares features with the sugar moiety of pineapple stem bromelain, a plant glycoprotein whose carbohydrate structure has been determined. A mutation was identified that eliminates staining by the antibody in imaginal and adult neural tissue. Tissue specific glycoconjugates, although widespread in the animal kingdom, are little understood. This mutation provides a unique opportunity to address the consequences of altering a neural specific carbohydrate moiety in an otherwise intact and behaving animal. The mutation maps to 84F. A second mutation, contained on the third chromosome balancer, TM3, eliminates anti‐HRP staining in embryos. These mutations appear to be separate genes.