We identified loss-of-function mutations in ATP6V0A2, encoding the a2 subunit of the V-type H+ ATPase, in several families with autosomal recessive cutis laxa type II or wrinkly skin syndrome. The mutations result in abnormal glycosylation of serum proteins (CDG-II) and cause an impairment of Golgi trafficking in fibroblasts from affected individuals. These results indicate that the a2 subunit of the proton pump has an important role in Golgi function.

The conserved oligomeric Golgi (COG) complex is a heterooctameric complex that regulates intraGolgi trafficking and the integrity of the Golgi compartment in eukaryotic cells. Here, we describe a patient with a mild form of congenital disorder of glycosylation type II (

The conserved oligomeric Golgi (COG) complex is a hetero-octameric complex essential for normal glycosylation and intra-Golgi transport. An increasing number of congenital disorder of glycosylation type II (CDG-II) mutations are found in COG subunits indicating its importance in glycosylation. We report a new CDG-II patient harbouring a p.R729W missense mutation in COG4 combined with a submicroscopical deletion. The resulting downregulation of COG4 expression additionally affects expression or stability of other lobe A subunits. Despite this, full complex formation was maintained albeit to a lower extent as shown by glycerol gradient centrifugation. Moreover, our data indicate that subunits are present in a cytosolic pool and full complex formation assists tethering preceding membrane fusion. By extending this study to four other known COG-deficient patients, we now present the first comparative analysis on defects in transport, glycosylation and Golgi ultrastructure in these patients. The observed structural and biochemical abnormalities correlate with the severity of the mutation, with the COG4 mutant being the mildest. All together our results indicate that intact COG complexes are required to maintain Golgi dynamics and its associated functions. According to the current CDG nomenclature, this newly identified deficiency is designated CDG-IIj.

Phosphomannomutase 2 (PMM2-CDG) is the most common congenital disorder of N-glycosylation and is caused by a deficient PMM2 activity. The clinical presentation and the onset of PMM2-CDG vary among affected individuals ranging from a severe antenatal presentation with multisystem involvement to mild adulthood presentation limited to minor neurological involvement. Management of affected patients requires a multidisciplinary approach. In this article, a systematic review of the literature on PMM2-CDG was conducted by a group of international experts in different aspects of CDG. Our managment guidelines were initiated based on the available evidence-based data and experts' opinions. This guideline mainly addresses the clinical evaluation of each system/organ involved in PMM2-CDG, and the recommended management approach. It is the first systematic review of current practices in PMM2-CDG and the first guidelines aiming at establishing a practical approach to the recognition, diagnosis and management of PMM2-CDG patients.