Thus, our results demonstrate, for the first time, that Gdt1p is required for both N-linked and O-linked protein glycosylation at a high external calcium concentration and are consistent with the fact that mutation in the human ortholog, TMEM165, is linked to a genetic disease (Congenital Disorders of Glycosylation) that is caused by defects in glycosylation16. The gene discussed is TMEM165; the disease is congenital disorder of glycosylation.