Lysosomal storage diseases. Glycoproteinoses — oligosaccharidoses

The epidemiology, clinical, biochemical and molecular genetic characteristics of oligosaccharidoses are presented — a group of rare autosomal recessive lysosomal diseases, includes sialidosis, mannosidosis, fucosidosis, aspartylglucosaminuria and α-N-acetylgalactosaminidase deficiency. All these diseases are caused by impaired catabolism of glycoproteins and excessive accumulation of various types of oligosaccharides in lysosomes. Clinically, they are characterized by progressive neuropsychiatric disorders combined with a mild gurler-like phenotype. Two genetically heterogeneous variants of alpha- and beta-mannosidosis are caused by mutations in the MAN2B1 and MANBA genes, respectively, and hereditary deficiency of two related α- and β-mannosidases. The cause of the development of fucosidosis is inactivating mutations in the FUCA1 gene, leading to deficiency of lysosomal α-L-fucosidase and accumulation of fucoglycoproteins and fucoglycolipids. The pathogenesis of aspartylglucosaminuria is associated with impaired catabolism of aspartylglucosamine and its accumulation in the lysosomes of liver, spleen, thyroid, kidney and brain cells. The cause of α-N-acetylgalactosaminidase deficiency is mutations in the NAGA gene and the accumulation of uncleaved glycoconjugants in lysosomes. A description of existing experimental models is presented and their role in studying the pathogenesis of these severe lysosomal diseases and the development of various therapeutic approaches is discussed. The most successful treatment for alpha-mannosidosis has been enzyme replacement therapy using a recombinant enzyme — velmanase alfa, which has already passed phase III clinical trials and is used in clinical practice. Pathogenetic treatments for the other oligosaccharidoses discussed here have not been described, although preclinical trials have shown promise for hematopoietic stem cell transplantation and gene therapy for the treatment of β-mannosidosis and aspartyl glucosaminuria, respectively.