Although both ppGalNAc-T2 and -T3 glycosylate the mucin-like domain of CST1 and other parasite proteins, the cyst wall rigidity phenotype is most likely due to the reduced glycosylation of the CST1 mucin-like domain, as our previous data revealed that deletion of the mucin-like domain from CST1 was sufficient in itself to cause the fragile cyst phenotype (9). The gene discussed is MUC5AC; the disease is cyst.