Muscle-eye-brain disease (MEB) is a degenerative muscle condition, a type of congenital muscular dystrophy. It affects the skeletal muscles, hinders brain development, and causes vision abnormalities.
The alpha-dystroglycan protein
MEB is a dystroglycanopathy, a disorder caused by the improper functioning of the alpha-dystroglycan protein.
Alpha-dystroglycan plays a vital role in the muscles that control movement (skeletal muscles) and the brain. It provides support and stabilizes the skeletal muscle fibers, helping them maintain their structure and aiding proper development, which is responsible for body movement.
It also directs the migration of nerve cells in the brain. The proper migration of nerve cells in the brain is vital, especially in the early stages of brain development. Any issues with alpha-dystroglycan interfere with its functioning and cause the progressive degeneration of the skeletal muscles and impede brain development.
Although the function of alpha-dystroglycan in the eye is unclear, any problems with its functioning also cause eye problems.
MEB and alpha-dystroglycan
To function correctly, alpha-dystroglycan has to be modified by the addition of a sugar molecule in a process called glycosylation. Several enzymes have been described that are responsible for the glycosylation of alpha-dystroglycan.
MEB is the result of a mutation in the POMGnT1 gene, which carries the instructions necessary to make one such alpha-dystroglycan-modifying enzyme. This enzyme is called O-linked mannose N-acetylglucosaminyltransferase 1. The mutation in the POMGnT1 gene leads to the production of a protein that fails to modify alpha-dystroglycan correctly and renders it non-functional.
Last updated: Aug. 23, 2019
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