What are the genetic changes related to mucopolysaccharidosis type VII ?
Mutations in the GUSB gene cause MPS VII. This gene provides instructions for producing the beta-glucuronidase (-glucuronidase) enzyme, which is involved in the breakdown of large sugar molecules called glycosaminoglycans (GAGs). GAGs were originally called mucopolysaccharides, which is where this condition gets its name. Mutations in the GUSB gene reduce or completely eliminate the function of -glucuronidase. The shortage (deficiency) of -glucuronidase leads to the accumulation of GAGs within cells, specifically inside the lysosomes. Lysosomes are compartments in the cell that digest and recycle different types of molecules. Conditions such as MPS VII that cause molecules to build up inside the lysosomes are called lysosomal storage disorders. The accumulation of GAGs increases the size of the lysosomes, which is why many tissues and organs are enlarged in this disorder. Researchers believe that the GAGs may also interfere with the functions of other proteins inside the lysosomes and disrupt many normal functions of cells.