The POMT1 gene provides instructions for making one piece of the protein O-mannosyltransferase (POMT) enzyme complex. The other piece is produced from the POMT2 gene. This enzyme complex is present in many different tissues in the body but is particularly abundant in the muscles used for movement (skeletal muscles), fetal brain, and testes.
The POMT complex helps modify a protein called alpha (α)-dystroglycan. Specifically, this complex adds a sugar molecule called mannose to α-dystroglycan through a process called glycosylation. Glycosylation is critical for the normal function of α-dystroglycan.
The α-dystroglycan protein helps anchor the structural framework inside each cell (cytoskeleton) to the lattice of proteins and other molecules outside the cell (extracellular matrix). In skeletal muscles, glycosylated α-dystroglycan helps stabilize and protect muscle fibers. In the brain, it helps direct the movement (migration) of nerve cells (neurons) during early development.
Health Conditions Related to Genetic Changes
At least 24 mutations in the POMT1 gene have been found to cause Walker-Warburg syndrome, the most severe form of a group of disorders known as congenital muscular dystrophies. Individuals with Walker-Warburg syndrome have skeletal muscle weakness and abnormalities of the brain and eyes. Because of the severity of the problems caused by this condition, affected individuals usually do not survive past early childhood.
POMT1 gene mutations that cause Walker-Warburg syndrome lead to the formation of nonfunctional POMT enzyme complexes that cannot transfer mannose to α-dystroglycan, preventing its normal glycosylation. As a result, α-dystroglycan can no longer effectively anchor cells to the proteins and other molecules that surround them. Without functional α-dystroglycan to stabilize the muscle fibers, they become damaged as they repeatedly contract and relax with use. The damaged fibers weaken and die over time, which affects the development, structure, and function of skeletal muscles in people with Walker-Warburg syndrome.
Defective α-dystroglycan also affects the migration of neurons during the early development of the brain. Instead of stopping when they reach their intended destinations, some neurons migrate past the surface of the brain into the fluid-filled space that surrounds it. Researchers believe that this problem with neuronal migration causes a brain abnormality called cobblestone lissencephaly, in which the surface of the brain lacks the normal folds and grooves and instead appears bumpy and irregular. Less is known about the effects of POMT1 gene mutations in other parts of the body.More About This Health Condition
Limb-girdle muscular dystrophy
MedlinePlus Genetics provides information about Limb-girdle muscular dystrophyMore About This Health Condition
Mutations in the POMT1 gene are also involved in less severe forms of muscular dystrophy, including muscle-eye-brain disease and POMT1-related congenital muscular dystrophy (also known as MDDGB1). Muscle-eye-brain disease is similar to Walker-Warburg syndrome (described above), although affected individuals usually survive into childhood or adolescence. POMT1-related congenital muscular dystrophy causes muscle weakness, brain abnormalities, and intellectual disability, but usually does not affect the eyes.
POMT1 gene mutations that cause these conditions result in POMT enzyme complexes with reduced function. As a result, glycosylation of α-dystroglycan is impaired. The severity of the resulting condition appears to be related to the level of α-dystroglycan glycosylation; the less glycosylation, the more severe the condition.
Other Names for This Gene
- dolichyl-phosphate-mannose--protein mannosyltransferase 1
- dolichyl-phosphate-mannose-protein mannosyltransferase
- protein O-mannosyl-transferase 1
- protein-O-mannosyltransferase 1
Additional Information & Resources
Tests Listed in the Genetic Testing Registry
Scientific Articles on PubMed
Catalog of Genes and Diseases from OMIM
- Akasaka-Manya K, Manya H, Endo T. Mutations of the POMT1 gene found in patients with Walker-Warburg syndrome lead to a defect of protein O-mannosylation. Biochem Biophys Res Commun. 2004 Dec 3;325(1):75-9. doi: 10.1016/j.bbrc.2004.10.001. Citation on PubMed
- Akasaka-Manya K, Manya H, Nakajima A, Kawakita M, Endo T. Physical and functional association of human protein O-mannosyltransferases 1 and 2. J Biol Chem. 2006 Jul 14;281(28):19339-45. doi: 10.1074/jbc.M601091200. Epub 2006 May 12. Citation on PubMed
- Balci B, Uyanik G, Dincer P, Gross C, Willer T, Talim B, Haliloglu G, Kale G, Hehr U, Winkler J, Topaloglu H. An autosomal recessive limb girdle muscular dystrophy (LGMD2) with mild mental retardation is allelic to Walker-Warburg syndrome (WWS) caused by a mutation in the POMT1 gene. Neuromuscul Disord. 2005 Apr;15(4):271-5. doi: 10.1016/j.nmd.2005.01.013. Citation on PubMed
- Bello L, Melacini P, Pezzani R, D'Amico A, Piva L, Leonardi E, Torella A, Soraru G, Palmieri A, Smaniotto G, Gavassini BF, Vianello A, Nigro V, Bertini E, Angelini C, Tosatto SC, Pegoraro E. Cardiomyopathy in patients with POMT1-related congenital and limb-girdle muscular dystrophy. Eur J Hum Genet. 2012 Dec;20(12):1234-9. doi: 10.1038/ejhg.2012.71. Epub 2012 May 2. Citation on PubMed or Free article on PubMed Central
- Kim DS, Hayashi YK, Matsumoto H, Ogawa M, Noguchi S, Murakami N, Sakuta R, Mochizuki M, Michele DE, Campbell KP, Nonaka I, Nishino I. POMT1 mutation results in defective glycosylation and loss of laminin-binding activity in alpha-DG. Neurology. 2004 Mar 23;62(6):1009-11. doi: 10.1212/01.wnl.0000115386.28769.65. Citation on PubMed
- Lommel M, Cirak S, Willer T, Hermann R, Uyanik G, van Bokhoven H, Korner C, Voit T, Baric I, Hehr U, Strahl S. Correlation of enzyme activity and clinical phenotype in POMT1-associated dystroglycanopathies. Neurology. 2010 Jan 12;74(2):157-64. doi: 10.1212/WNL.0b013e3181c919d6. Citation on PubMed
- Manya H, Chiba A, Yoshida A, Wang X, Chiba Y, Jigami Y, Margolis RU, Endo T. Demonstration of mammalian protein O-mannosyltransferase activity: coexpression of POMT1 and POMT2 required for enzymatic activity. Proc Natl Acad Sci U S A. 2004 Jan 13;101(2):500-5. doi: 10.1073/pnas.0307228101. Epub 2003 Dec 29. Citation on PubMed or Free article on PubMed Central