Interestingly, although TxgGalNAc-T3H333A results in diminished activity in vitro (Fig. 2d), it does not completely abolish cyst wall O-glycosylation in vivo, suggesting the presence of additional co-factors or conditions that influence TxgGalNAc-T3 function in vivo. The gene discussed is SLC25A5; the disease is cyst.