Congenital Disorder of Glycosylation

CDG means Congenital Disorders of Glycosylation, which literally means congenital disorders of glycosylation. Glycosylation is the linkage of sugar chains with different biomolecules such as proteins ( protein ) and fats. There are different bonds of sugar chains to proteins. The known diseases of the glycosylation is predominantly N- glycosylation (N for the amino group of the amino acid asparagine), wherein the sugar chain (N- glycans ) at the amino acid asparagine with other amino acids can be synthesized in a specific sequence. The initial steps of the assembly of the N- glycans made ​​in the endoplasmic reticulum in a localized in the membrane of the ER lipid anchor, the dolichol. Only then the glycan is transferred to the protein. The completion of N- glycans is completed in the Golgi apparatus.

In the so-called O-glycosylation (O for the hydroxy group of the amino acid ), sugars are mainly synthesized in the amino acids serine and threonine, the structure of the O- glycans takes place almost exclusively in the Golgi apparatus. It is estimated that approximately 1 % of all genes encoding proteins involved in Glykosylierungsprozessen.

Sugar chains play an essential role in numerous proteins, so there are, for example, the blood group A, B and O from different sugar chains. Numerous other proteins associated with sugar chains, and are accordingly called glycoproteins. Since the function of many glycoproteins is limited in the absence or failure of the sugar chains, diseases result from CDG often numerous failures. However, there are also diseases that affect only one organ or cell system.

The first CDG was founded in 1995 and molecularly characterized biochemically by the Belgian pediatrician J. Jaeken. Since then, numerous other disorders of glycosylation have been described as a distinct disease entities. Already, over 17 CDG have been described and in rapid succession new diseases are discovered. The elucidation of new CDG made ​​in 2000, the renaming of the diseases of former Carbohydrate Deficient Glycoprotein Syndrome ( CDG syndromes, CDGS ) to Congenital Disorders of Glycosylation necessary. The abbreviation CDG was retained. The new classification is based on the intracellular localization of the molecular defect. Disturbances in the structure of the oligosaccharide backbone in the endoplasmic reticulum as a CDG -I, disorders of the modification of the oligosaccharides in the endoplasmic reticulum and Golgi apparatus termed CDG -II. The discovered CDG are in small letters of the order of discovery by named (CDG Ia, description in 1995, CDG Ib Description 1998 etc. ) In all known CDG is an autosomal recessive mode of inheritance before.