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The official name of this gene is “glucan (1,4-alpha-), branching enzyme 1.”
GBE1 is the gene's official symbol. The GBE1 gene is also known by other names, listed below.
The GBE1 gene provides instructions for making the glycogen branching enzyme. This enzyme is involved in the last step of the production of a complex sugar called glycogen, which is a major source of stored energy in the body. Glycogen is made up of many molecules of a simple sugar called glucose; some glucose molecules are linked together in a straight line, while others branch off the main line and form side chains. The glycogen branching enzyme is involved in the formation of these side chains. The branched structure of glycogen makes it more compact for storage and allows it to break down more easily when it is needed for fuel.
At least three mutations in the GBE1 gene have been found to cause adult polyglucosan body disease, a condition that affects the nervous system. These mutations change single protein building blocks (amino acids) in the glycogen branching enzyme. One mutation appears to be more common in affected people with Ashkenazi Jewish ancestry. This mutation replaces the amino acid tyrosine with the amino acid serine at position 329 in the enzyme (written Tyr329Ser or Y329S). Most mutations that cause adult polyglucosan body disease lead to a shortage (deficiency) of the enzyme. As a result, glycogen has fewer side chains. These abnormal glycogen molecules, called polyglucosan bodies, accumulate within cells and cause damage. Nerve cells (neurons) appear to be particularly vulnerable to the accumulation of polyglucosan bodies in this disorder. Damage to neurons causes reduced sensation, weakness, and other nervous system problems in people with adult polyglucosan body disease.
Approximately 40 mutations in the GBE1 gene have been found to cause glycogen storage disease type IV (GSD IV). This disorder is characterized by liver and muscle problems that usually begin in infancy and are caused by a buildup of abnormal glycogen. Most of the mutations that cause this condition change single amino acids in the glycogen branching enzyme. The GBE1 gene mutations that cause GSD IV lead to a severe shortage or complete absence of glycogen branching enzyme. As a result, polyglucosan bodies accumulate in cells, leading to damage and cell death. Polyglucosan bodies build up in cells throughout the body, but liver cells and muscle cells are most severely affected in GSD IV. Glycogen accumulation in the liver interferes with liver functioning, causing an enlarged liver and liver disease. The inability of muscle cells to break down glycogen for energy leads to muscle weakness and wasting.
It is unclear why liver and muscle cells are affected by the accumulation of polyglucosan bodies in GSD IV, while neurons are solely affected in adult polyglucosan body disease (described above).
Cytogenetic Location: 3p12.3
Molecular Location on chromosome 3: base pairs 81,489,698 to 81,761,798
The GBE1 gene is located on the short (p) arm of chromosome 3 at position 12.3.
More precisely, the GBE1 gene is located from base pair 81,489,698 to base pair 81,761,798 on chromosome 3.
See How do geneticists indicate the location of a gene? (http://ghr.nlm.nih.gov/handbook/howgeneswork/genelocation) in the Handbook.
You and your healthcare professional may find the following resources about GBE1 helpful.
You may also be interested in these resources, which are designed for genetics professionals and researchers.
See How are genetic conditions and genes named? (http://ghr.nlm.nih.gov/handbook/mutationsanddisorders/naming) in the Handbook.
acids ; amino acid ; Ashkenazi Jewish ; cell ; deficiency ; enzyme ; gene ; glucose ; glycogen ; mutation ; nervous system ; protein ; serine ; simple sugar ; tyrosine ; wasting
You may find definitions for these and many other terms in the Genetics Home Reference Glossary (http://ghr.nlm.nih.gov/glossary).
The resources on this site should not be used as a substitute for professional medical care or advice. Users seeking information about a personal genetic disease, syndrome, or condition should consult with a qualified healthcare professional. See How can I find a genetics professional in my area? (http://ghr.nlm.nih.gov/handbook/consult/findingprofessional) in the Handbook.