The SLC7A9 gene helps the kidneys move certain amino acids, especially cystine, back into the body instead of letting them spill into urine. This gene plays an important role in keeping urine from becoming overloaded with cystine. If the gene does not work properly, cystine can collect in the urine and form crystals or stones in the kidneys, ureters, or bladder. Pathogenic variants in the SLC7A9 gene can cause cystinuria, an inherited condition that often leads to repeated kidney stones.
What is a gene?
Genes are stretches of DNA that carry instructions cells use to make molecules or regulate processes in the body. Some provide the code for proteins, which do much of the cell’s work. Others are used mainly to guide when certain processes happen, where they happen, and how active they are. In combination, genes affect how the body develops and functions, and they can also influence how you react to food, stress, or medications. For a deeper look at this subject, you can find more in the LearnHub.
Overview
SLC7A9Gene function
What if the gene works
The SLC7A9 gene helps kidney and small intestine cells move cystine and certain amino acids. This supports reabsorption from urine and uptake from food, which helps keep amino acid levels balanced and lowers cystine buildup.
Risk
What if the gene does not work
Variants in the SLC7A9 gene can cause cystinuria, which raises cystine in urine and often leads to recurrent kidney stones. Effects can range from milder to more severe, influencing when stones begin and how often they come back.
Treatment
What does that mean for your treatment
No SLC7A9-specific treatment or drug choice is currently established. In practice, care for cystinuria is the same whether a pathogenic variant is in the SLC7A9 gene or another cystinuria gene, and the SLC7A9 gene remains mainly a research target.
Conditions associated with SLC7A9
Gene function
What if the gene works
Your kidneys and small intestine use the SLC7A9 gene to move a small group of amino acids into cells. These amino acids include cystine, lysine, arginine, and ornithine, which the body uses as basic building blocks. Understanding how the SLC7A9 gene works can make it easier to see how your body saves useful nutrients instead of losing them.
The SLC7A9 gene provides one part of a transporter in the cell membrane. This transporter moves cystine, lysine, arginine, and ornithine from one side of the membrane to the other.
In the kidneys, this system helps the kidneys reabsorb cystine and other amino acids from the forming urine into kidney cells. That recycling step supports normal amino acid balance and helps the body hold on to useful nutrients.
In the small intestine, the same transport system helps absorb these amino acids from digested food. This supports your body’s supply of raw materials for proteins and other routine cell work.
Its protein pairs with the protein made by the SLC3A1 gene to form a working transporter at the cell surface. This partnership helps the transporter reach the right place and carry amino acids more effectively.
What is a variant?
A genetic variant is a small alteration in the DNA sequence of a gene. These changes are common and help create normal human diversity, including differences in appearance, metabolism, and how the body responds to environmental influences. Many variants do not have any noticeable effect and are simply part of natural genetic variation. In some situations, though, a variant can change how a gene functions more substantially and may contribute to or cause a genetic condition.
Genetic variants
What if the gene does not work
Variants in the SLC7A9 gene can change the shape, stability, or cell-surface delivery of its transporter protein, so kidney and intestinal cells reabsorb cystine and certain amino acids less effectively. Some variants only partly reduce transport, while more severe variants can leave little or no activity, which may lead to earlier or more frequent cystine stones. This helps explain how SLC7A9 gene variants affect protein function and why cystinuria can vary from person to person.
How variants are linked to conditions
Pathogenic variants in the SLC7A9 gene cause cystinuria, an inherited condition linked to recurring kidney stones, often beginning in childhood or early adulthood. Many people with SLC7A9-related cystinuria have stone pain, blood in the urine, or repeated urinary blockage from stones, although symptoms can vary widely. This well-established SLC7A9 gene kidney stone association is the gene’s main confirmed health link.
A variant is not necessarily a diagnosis
Genetic variants are common across the general population and are a normal feature of human biology. Most do not directly affect health and simply contribute to natural differences among people. For many genes, having a variant associated with a condition points to a possible link rather than a certain diagnosis, particularly when several genes and environmental influences play a role. Still, in some situations, one well-characterized variant in a particular gene is enough to confirm a diagnosis.
Are there things that can increase or change my risk?
For people with harmful changes in the SLC7A9 gene, the main day-to-day risk is forming cystine kidney stones. Stone risk can rise with low fluid intake, high salt, and a diet heavy in animal protein, while keeping urine dilute and less acidic can help lower the chance of stones.
Inheritance of SLC7A9 variants
How SLC7A9 variants are inherited can be less straightforward than a simple single pattern. In SLC7A9-related cystinuria, many affected people have variants in both copies of the SLC7A9 gene, which fits an autosomal recessive pattern, but some people with one altered copy also have increased cystine in the urine and may form kidney stones, so some families can look closer to autosomal dominant with reduced penetrance. Because the SLC7A9 gene is on chromosome 19, a child receives one copy from each parent.
What does my SLC7A9 result mean for my family?
For SLC7A9, family meaning usually centers on cystinuria, an inherited condition that can lead to kidney stones. Close relatives, especially brothers and sisters, may also have the condition or carry a changed copy of the gene even if they have never had symptoms. Parents are often carriers, and children are more likely to be carriers unless the other parent also carries a change in SLC7A9.
Genetic information
Genetic testing
How you find out about variants
To find out whether you carry a variant in the SLC7A9 gene, doctors use SLC7A9 genetic testing for cystinuria with a blood sample, saliva sample, or cheek swab. A lab reads the DNA code in the SLC7A9 gene and looks for changes linked to the condition.
When should I consider getting a genetic test?
Genetic testing for the SLC7A9 gene may be worth considering if someone has repeated cystine kidney stones, especially starting in childhood or the teen years. It can also help when kidney stones run in the family or when urine testing suggests cystinuria, a condition that causes too much cystine in the urine.
A genetic result is only one part of your health story
A genetic result can provide useful insight, but what it can tell you depends on the condition and the type of variant involved. Lifestyle, environment, age, and medical history, among other influences, shape how the body functions over time. In some conditions, especially those shaped by many genes, genetic information provides context rather than certainty and is most useful when considered alongside other parts of care. In other situations, a genetic result may offer a clear answer. In areas like medication response, genetic results can also help put individual experiences into context.
Pharmacogenetics
How variants shape your response to medicine
Genetic variation can affect how your body responds to medicines. This helps explain why the same treatment works well for one person, seems less helpful for another, or causes more side effects in someone else. In some cases, inherited differences change how the body absorbs, breaks down, or moves a drug, which can influence how strongly it works or how sensitive a person is to it.
What is Pharmacogenetics?
Pharmacogenetics examines how differences in a person’s genes can shape their response to medicines. By studying links between genes and drugs, it helps explain why the same treatment may not work in the same way for everyone. With many medications, genes can influence how the body handles a drug or how much effect it has. This information can support treatment choices that are more informed and more personalized. More detail is available in the LearnHub.
Drugs influenced by the SLC7A9 gene
When should I seek medical advice?
There is not yet a broadly confirmed role for this gene in guiding medication response. Questions about medicines, side effects, or your overall health are best discussed with your doctor or pharmacist.
History
SLC7A9 entered medical genetics through research on cystinuria, an inherited cause of recurring kidney stones that had been recognized for many years before the gene itself was identified. In the late 1990s, researchers showed that not all families with cystinuria had changes in the same gene, which helped explain why the condition could look different from one person to another. Building on this early work, scientists uncovered more about the gene. The discovery of the SLC7A9 gene, alongside the related SLC3A1 gene, marked an important step in understanding that cystinuria has more than one genetic cause. That shift improved genetic classification and shaped how laboratories interpret test results today.