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ALG12 gene

ALG12 alpha-1,6-mannosyltransferase

Normal Function

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.

Health Conditions Related to Genetic Changes

ALG12-congenital disorder of glycosylation

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.

More About This Health Condition

Other Names for This Gene

  • 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
  • CDG1G
  • 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
  • dolichyl-P-Man:Man(7)GlcNAc(2)-PP-dolichyl-alpha-1,6-mannosyltransferase
  • dolichyl-P-mannose:Man-7-GlcNAc-2-PP-dolichyl-alpha-6-mannosyltransferase
  • ECM39
  • hALG12
  • mannosyltransferase ALG12 homolog
  • membrane protein SB87
  • PP14673

Additional Information & Resources

Tests Listed in the Genetic Testing Registry

Scientific Articles on PubMed

Catalog of Genes and Diseases from OMIM

Gene and Variant Databases


  • Chantret I, Dupre T, Delenda C, Bucher S, Dancourt J, Barnier A, Charollais A, Heron D, Bader-Meunier B, Danos O, Seta N, Durand G, Oriol R, Codogno P, Moore SE. Congenital disorders of glycosylation type Ig is defined by a deficiency in dolichyl-P-mannose:Man7GlcNAc2-PP-dolichyl mannosyltransferase. J Biol Chem. 2002 Jul 12;277(28):25815-22. doi: 10.1074/jbc.M203285200. Epub 2002 Apr 30. Citation on PubMed
  • Grubenmann CE, Frank CG, Kjaergaard S, Berger EG, Aebi M, Hennet T. ALG12 mannosyltransferase defect in congenital disorder of glycosylation type lg. Hum Mol Genet. 2002 Sep 15;11(19):2331-9. doi: 10.1093/hmg/11.19.2331. Citation on PubMed
  • Thiel C, Schwarz M, Hasilik M, Grieben U, Hanefeld F, Lehle L, von Figura K, Korner C. Deficiency of dolichyl-P-Man:Man7GlcNAc2-PP-dolichyl mannosyltransferase causes congenital disorder of glycosylation type Ig. Biochem J. 2002 Oct 1;367(Pt 1):195-201. doi: 10.1042/BJ20020794. Citation on PubMed or Free article on PubMed Central

The information on this site should not be used as a substitute for professional medical care or advice. Contact a health care provider if you have questions about your health.