The ALG12 gene provides instructions for making an enzyme that is involved in a process called glycosylation. During this process, complex chains of sugar molecules (oligosaccharides) are attached to proteins and fats (lipids). Glycosylation modifies proteins so they can fully perform their functions. Oligosaccharides are made up of many sugar molecules that are attached to one another in a stepwise process, forming a complex chain. The enzyme produced from the ALG12 gene transfers a simple sugar called mannose to growing oligosaccharides at a particular step in the formation of the chain. Once the correct number of sugar molecules are linked together, the oligosaccharide is attached to a protein or lipid.
At least 13 mutations in the ALG12 gene have been found to cause ALG12-congenital disorder of glycosylation (ALG12-CDG). This condition typically leads to delayed growth and development, weak muscle tone (hypotonia), and other signs and symptoms. Mutations in the ALG12 gene result in the production of an abnormal enzyme with little activity. Without a properly functioning enzyme, mannose cannot be added to the chain efficiently, and the resulting oligosaccharides are often incomplete. Although the short oligosaccharides can be transferred to proteins and lipids, the process is not as efficient as with the full-length oligosaccharide. As a result, glycosylation is reduced. The wide variety of signs and symptoms in ALG12-CDG are likely due to impaired glycosylation of proteins and lipids that are needed for normal function in many organs and tissues, including the brain.
- asparagine-linked glycosylation 12 homolog (S. cerevisiae, alpha-1,6-mannosyltransferase)
- asparagine-linked glycosylation 12 homolog (yeast, alpha-1,6-mannosyltransferase)
- asparagine-linked glycosylation 12, alpha-1,6-mannosyltransferase homolog
- asparagine-linked glycosylation protein 12 homolog
- dol-P-Man dependent alpha-1,6-mannosyltransferase
- dol-P-Man:Man(7)GlcNAc(2)-PP-Dol alpha-1,6-mannosyltransferase
- dolichyl-P-Man:Man(7)GlcNAc(2)-PP-dolichol alpha-1,6-mannosyltransferase
- mannosyltransferase ALG12 homolog
- membrane protein SB87