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SLC25A13 gene
Reviewed by Medicinsk Expert•Last updated: 2026-10-22•Gene

SLC25A13 Gene

The SLC25A13 gene provides instructions for making the protein citrin, which is essential for transporting molecules in and out of mitochondria to support energy production and nitrogen processing.

Overview

The SLC25A13 gene, also known as solute carrier family 25 member 13, is located on chromosome 7. It encodes a protein called citrin, which 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.

Normal Function

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 the urea cycle. The urea cycle is a sequence of chemical reactions that takes place in liver cells. These reactions process excess nitrogen 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
  • Making proteins
  • Producing nucleotides, which are the building blocks of DNA and RNA

Health Conditions Related to Genetic Changes

Citrullinemia

More than 20 mutations in the SLC25A13 gene have been identified in people with adult-onset type II citrullinemia. This condition causes neurological problems, such as confusion, restlessness, irritability, and seizures, usually beginning in adulthood. 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 neurological problems in people with adult-onset type II citrullinemia.

Neonatal Intrahepatic Cholestasis Caused by Citrin Deficiency (NICCD)

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 go away within a year. In rare cases, these individuals develop signs and symptoms of another condition called failure to thrive and dyslipidemia caused by citrin deficiency (FTTDCD) after recovering from NICCD. Many individuals with NICCD or FTTDCD 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 or FTTDCD develop the features of adult-onset type II citrullinemia.

Other Names for This Gene

  • ARALAR2
  • calcium-binding mitochondrial carrier protein Aralar2
  • CITRIN
  • CMC2_HUMAN
  • CTLN2
  • mitochondrial aspartate glutamate carrier 2
  • solute carrier family 25 (aspartate/glutamate carrier), member 13

Frequently Asked Questions

dult‑onset type II citrullinemia is inherited in an autosomal recessive manner. If one parent is affected and the other is a carrier, each child has a 50% chance of being a carrier and a 0% chance of being affected; if both parents are carriers, there is a 25% risk of an affected child. Genetic counseling and carrier testing are advised.
Stressors that increase protein catabolism—such as infections, fasting, high‑protein meals, alcohol intake, or certain medications—can raise blood ammonia and citrulline levels, precipitating confusion, irritability, seizures, or coma in affected individuals.
low‑protein diet (typically 0.6–0.8 g/kg/day) with adequate calories from carbohydrates and fats is recommended, along with avoidance of fasting. Supplementation with arginine or citrulline may be prescribed to support the urea cycle, but this should be individualized by a metabolic specialist.
Intravenous sodium benzoate or sodium phenylacetate, which facilitate alternative pathways for nitrogen excretion, are commonly used in emergencies. Additionally, arginine supplementation and, in severe cases, hemodialysis may be required under specialist supervision.
Source: MedlinePlus, National Library of Medicine

MedlinePlus brings together authoritative health information from the National Library of Medicine (NLM), the National Institutes of Health (NIH), and other government agencies and health-related organizations.

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