Identification of the first COG–CDG patient of Indian origin

Mutations in the Conserved Oligomeric Golgi (COG) complex give rise to type II congenital disorders of glycosylation (CDG). Thus far, mutations have been identified in 6 of the 8 COG subunits. Here we present data identifying a previously reported CDG-IIx case from Singapore as a new COG4 patient with 2 novel mutations leading to p.E233X and p.L773R; with p.E233X being a de novo mutation. As a result, COG4 protein expression was dramatically reduced, while expression of the other subunits remained unaffected. Analysis of serum N-glycans revealed deficiencies in both sialylation and galactosylation. Furthermore, patient fibroblasts have impaired O-glycosylation. Importantly, patient fibroblasts exhibited a delay in Brefeldin A (BFA) induced retrograde transport, a common characteristic seen in COG deficiencies.