|http://ghr.nlm.nih.gov/ A service of the U.S. National Library of Medicine®|
The official name of this gene is “galactosylceramidase.”
GALC is the gene's official symbol. The GALC gene is also known by other names, listed below.
The GALC gene provides instructions for making an enzyme called galactosylceramidase. Through a process called hydrolysis, this enzyme uses water molecules to break down certain fats called galactolipids, which are found primarily in the brain and kidneys.
Within cells, galactosylceramidase is found in enzyme-filled sacs called lysosomes where it hydrolyzes specific galactolipids, including galactosylceramide and psychosine. Galactosylceramide is an important component of myelin, the protective covering around certain nerve cells that ensures the rapid transmission of nerve impulses. Psychosine forms during the production of myelin, and then it breaks down with help of galactosylceramidase. Under normal conditions, tissues contain very little psychosine.
More than 70 GALC gene mutations that cause Krabbe disease have been identified. The most common mutation in affected individuals of European ancestry deletes a large segment of the GALC gene (written as 30-kb del). Other mutations insert additional DNA building blocks (base pairs) into the GALC gene, delete a small number of base pairs from the gene, or replace a single base pair with an incorrect base pair. These mutations severely reduce the activity of the galactosylceramidase enzyme. As a result, certain galactolipids such as galactosylceramide and psychosine cannot be broken down and accumulate in cells that make myelin. Research suggests that psychosine accumulation is toxic and damages myelin-producing cells, causing the loss of myelin. Without myelin, nerves in the brain and other parts of the body cannot function properly, leading to the signs and symptoms of Krabbe disease.
Some individuals with late-onset Krabbe disease have a particular mutation in one of the two copies of the GALC gene in each cell. This mutation replaces one of the building blocks (amino acids) used to make the galactosylceramidase enzyme. Specifically, the amino acid glycine is replaced with the amino acid aspartic acid at position 270 in the enzyme (written as Gly270Asp or G270D). The second copy of the GALC gene usually has a different mutation, such as the large 30-kb deletion. The Gly270Asp mutation probably allows some activity of the galactosylceramidase enzyme, which delays onset of the disease.
Cytogenetic Location: 14q31
Molecular Location on chromosome 14: base pairs 87,837,819 to 87,993,664
The GALC gene is located on the long (q) arm of chromosome 14 at position 31.
More precisely, the GALC gene is located from base pair 87,837,819 to base pair 87,993,664 on chromosome 14.
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 GALC 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 ; base pair ; cell ; deletion ; DNA ; enzyme ; galactolipids ; galactosylsphingosine ; gene ; glycine ; hydrolysis ; kb ; mutation ; psychosine ; toxic
You may find definitions for these and many other terms in the Genetics Home Reference Glossary (http://www.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.