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The official name of this gene is “solute carrier family 25 (aspartate/glutamate carrier), member 13.”
SLC25A13 is the gene's official symbol. The SLC25A13 gene is also known by other names, listed below.
The SLC25A13 gene provides instructions for making a protein called citrin. This protein is active chiefly in the liver, kidneys, and heart. Within the cells of these organs, citrin is involved in transporting molecules into and out of energy-producing structures called mitochondria. Specifically, citrin carries a protein building block (amino acid) called glutamate into mitochondria and transports the amino acid aspartate out of mitochondria as part of a process called the malate-aspartate shuttle.
An adequate supply of aspartate must be transported out of mitochondria to participate in a process called the urea cycle. The urea cycle is a sequence of chemical reactions that takes place in liver cells. These reactions process excess nitrogen that is generated as the body uses proteins. The excess nitrogen is used to make a compound called urea, which is excreted from the body in urine.
Citrin participates in several other important cellular functions as part of the malate-aspartate shuttle. This protein plays a role in producing and breaking down simple sugars and making proteins. It is also involved in the production of nucleotides, which are the building blocks of DNA and its chemical cousin, RNA.
The SLC25A13 gene belongs to a family of genes called SLC (solute carriers).
A gene family is a group of genes that share important characteristics. Classifying individual genes into families helps researchers describe how genes are related to each other. For more information, see What are gene families? (http://ghr.nlm.nih.gov/handbook/howgeneswork/genefamilies) in the Handbook.
More than 20 mutations in the SLC25A13 gene have been identified in people with adult-onset type II citrullinemia. Almost all of the identified mutations lead to the production of an unstable citrin protein that is quickly broken down or an abnormally short, nonfunctional version of the protein.
A lack of functional citrin blocks the malate-aspartate shuttle, including the transport of aspartate out of mitochondria. This loss of citrin inhibits the normal production of proteins and nucleotides. It also reduces the amount of aspartate available to take part in the urea cycle. As a result, the liver cannot effectively process excess nitrogen into urea. A disruption in the urea cycle allows nitrogen (in the form of ammonia) and other byproducts of the urea cycle (such as citrulline) to build up in the bloodstream. Ammonia is toxic, especially to the nervous system, which helps explain the development of abnormal behaviors and other neurologic problems in people with adult-onset type II citrullinemia.
Mutations in the SLC25A13 gene also have been found in infants with a liver disorder called neonatal intrahepatic cholestasis caused by citrin deficiency (NICCD). This liver disorder is also known as neonatal-onset type II citrullinemia. NICCD blocks the flow of bile (a digestive fluid produced by the liver) and prevents the body from processing certain nutrients properly. Ammonia does not build up in the bloodstream of infants with NICCD, and the signs and symptoms typically resolve within a year. Many infants with NICCD have the same mutations in the SLC25A13 gene as people with adult-onset type II citrullinemia. Years or even decades later, some people who had NICCD as infants develop the characteristic features of adult-onset type II citrullinemia.
Cytogenetic Location: 7q21.3
Molecular Location on chromosome 7: base pairs 95,749,531 to 95,951,458
The SLC25A13 gene is located on the long (q) arm of chromosome 7 at position 21.3.
More precisely, the SLC25A13 gene is located from base pair 95,749,531 to base pair 95,951,458 on chromosome 7.
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 SLC25A13 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.
amino acid ; ammonia ; bile ; calcium ; carrier ; compound ; deficiency ; digestive ; DNA ; gene ; mitochondria ; neonatal ; nervous system ; neurologic ; protein ; RNA ; solute ; toxic ; urea
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.