The GNMT gene helps your liver control methyl groups, small chemical tags your body uses to process nutrients and keep many cells working normally. It also helps balance methionine, an amino acid from food, and related chemicals in the blood. If the GNMT gene does not work properly, methionine levels can rise and some people may develop liver changes or mild developmental differences, while others have few noticeable symptoms.
What is a gene?
A gene is a piece of DNA that carries instructions your cells use to make molecules or regulate processes in the body. Some genes provide the information needed to make proteins, the parts of cells that do much of the work. Other genes mainly help control when and where certain processes happen, and how active those processes are. Taken together, genes influence how the body develops and functions, and they can also shape how you respond to food, stress, or medications. To explore this subject in more detail, you can find more in the LearnHub.
Overview
GNMTGene function
What if the gene works
The GNMT gene helps control how your body uses methyl groups, small chemical tags that support many cell functions. It is especially active in the liver, where it helps manage methionine and related nutrients.
Risk
What if the gene does not work
Variants in the GNMT gene can cause inherited hypermethioninemia, with high blood methionine and sometimes enlarged liver or mild liver injury. Milder or more severe variants may influence when findings appear and how much the liver is affected.
Treatment
What does that mean for your treatment
For pathogenic or loss-of-function variants in the GNMT gene, no gene-specific treatment or management approach is currently established in clinical guidelines. The GNMT gene is being studied in liver disease and liver cancer as a biomarker and possible drug target, but this has not changed routine treatment.
Conditions associated with GNMT
Gene function
What if the gene works
In everyday metabolism, your body uses the GNMT gene to manage small chemical tags called methyl groups. It is most active in the liver, where it helps keep key nutrient pathways running smoothly. This work supports balanced cell chemistry and steady amino acid use.
The GNMT gene helps control how quickly your cells use S-adenosylmethionine, or SAM (a major methyl donor). This keeps the supply of methyl groups balanced for many routine chemical reactions.
Its protein transfers a methyl group to glycine, turning it into sarcosine. This is the main chemical job of GNMT and a normal part of amino acid processing.
The GNMT gene is especially active in the liver, where it supports the pathway that recycles and shares methyl groups from food. In this way, GNMT gene function helps keep day to day metabolism steady.
What is a variant?
A genetic variant is a minor difference in the DNA sequence of a gene. These changes are common and are part of 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 simply reflect natural genetic variation. In some cases, though, a variant can change the function of a gene more substantially and may contribute to, or cause, a genetic condition.
Genetic variants
What if the gene does not work
Variants in the GNMT gene can lower or abolish the enzyme’s activity by changing its shape, making it unstable, or stopping the protein from being made in full. In studies of how GNMT gene variants affect enzyme activity, some changes leave partial function, while more disruptive variants cause little to no function. That range can influence whether GNMT deficiency is milder or more noticeable, and when signs first appear.
How variants are linked to conditions
Having two pathogenic variants in the GNMT gene causes a rare inherited condition called GNMT deficiency, also known as glycine N-methyltransferase deficiency. People with this condition usually have persistently high methionine levels in the blood, and some develop an enlarged liver, abnormal liver blood tests, or mild developmental differences. This is the main well-established condition in which GNMT gene variants are linked to high methionine levels and liver problems.
A variant is not necessarily a diagnosis
Genetic variants are common and are a normal part of human biology. Most do not directly affect health and instead reflect natural differences among people. For many genes, having a variant associated with a condition suggests a possible link rather than a certain diagnosis, especially when several genes and environmental factors contribute. In some cases, though, one well-characterized variant in a specific gene is enough to confirm a diagnosis.
Are there things that can increase or change my risk?
There is not yet broadly confirmed evidence on specific factors that increase or reduce health risks related to the GNMT gene. For inherited GNMT-related conditions, the main factor is whether someone was born with gene changes in both copies of GNMT, while day-to-day habits have not been shown to clearly change that underlying genetic risk.
Inheritance of GNMT variants
GNMT gene inheritance follows an autosomal recessive pattern for the well-established condition linked to this gene. This means a person usually inherits one GNMT variant from each parent. Parents who each carry one variant are often unaffected, and with each pregnancy they have a 25% chance of having a child with GNMT-related disease, a 50% chance of having a child who is a carrier, and a 25% chance of having a child with no familial variant. Because the GNMT gene is on chromosome 6, this pattern affects males and females equally.
What does my GNMT result mean for my family?
For families with GNMT-related disease, the pattern is recessive, which means parents are usually healthy carriers and brothers or sisters may also have the condition or be carriers. Other close relatives may be carriers too, especially on the side of the family where the gene change was passed down. This can matter for future pregnancies and for relatives who are planning children.
Genetic information
Genetic testing
How you find out about variants
To find out whether you carry a variant in the GNMT gene, genetic testing for variants in the GNMT gene uses a blood or saliva sample to read its DNA code. A lab checks for changes in the GNMT gene and reports whether a variant is present, often with a brief explanation of what the result may mean for you or your family.
When should I consider getting a genetic test?
Testing for changes in the GNMT gene may be considered when someone has very high methionine, a substance measured on blood tests, especially with unexplained liver problems or a family history of the same finding. It can also help clarify the cause when a baby or child has persistently high methionine on newborn screening or later testing.
A genetic result is only one part of your health story
Genetic test findings can be informative, but how much clarity they provide varies by the condition and the type of variant involved. Many factors, including lifestyle, environment, age, and medical history, influence how the body works over time. For some conditions, especially those shaped by many genes, genetic information offers context rather than certainty and is best understood together with other parts of care. In other situations, a genetic result may give a clear answer. In areas such as medication response, these results can also help put individual experiences into perspective.
Pharmacogenetics
How variants shape your response to medicine
Genetic variation can affect how your body responds to medicines. Small differences in DNA can change how quickly a drug is broken down, how strongly it acts, or how sensitive your body is to its effects. That helps explain why the same treatment works well for one person, works less well for another, or causes more side effects in someone else. These differences are common and are one part of the reason medication response can vary from person to person.
What is Pharmacogenetics?
Pharmacogenetics examines how genetic differences affect the way people respond to medicines. It looks at gene and drug patterns to help explain why the same treatment can work differently from one person to another. For many medications, genes influence both how strongly a drug works and how the body handles it. This information can support treatment decisions that are more informed and more individualized. More detail on this topic is available in the LearnHub.
Drugs influenced by the GNMT gene
When should I seek medical advice?
There is not yet strong, widely accepted evidence that changes in this gene should guide medicine choice or dosing, so any concerns about side effects, new symptoms, or how a treatment is working are best discussed with your doctor.
History
The GNMT gene entered the scientific literature through studies of a liver enzyme that researchers were characterizing in the mid 20th century. As biochemical methods improved, scientists linked that enzyme to a specific human gene and mapped its place in the genome. In recent decades, awareness of this gene’s role has grown through work on methyl group balance, liver biology, and inherited metabolic conditions. From these first observations, research expanded steadily, including animal studies that connected loss of GNMT activity with liver changes and tumor formation. These historical steps shaped today’s understanding of why GNMT is still studied in metabolism, liver disease, and cancer research.