The MAT1A gene helps the liver make SAMe, a substance your body uses in many chemical reactions. If the MAT1A gene does not work properly, methionine can build up in the blood, causing MAT I/III deficiency. Many people with this condition stay well, while some may have developmental, movement, or liver problems. Most people hear about this gene through newborn screening, when a blood test shows high methionine.
What is a gene?
A gene is a stretch of DNA that carries instructions your cells use to make molecules or regulate processes in the body. Some genes hold the information needed to produce proteins, the active parts of cells. Other genes mainly help decide when, where, and how strongly certain processes take place. Together, genes affect how the body develops and works, and they can shape how you respond to food, stress, or medications. To explore this subject in more detail, you can learn more in the LearnHub.
Overview
MAT1AGene function
What if the gene works
The MAT1A gene helps the liver make SAMe, a molecule used to process methionine and support many chemical reactions. This helps normal liver function and the handling of proteins and other nutrients.
Risk
What if the gene does not work
Variants in the MAT1A gene can cause MAT I/III deficiency, which raises methionine levels in the blood. Milder variants may cause few or no symptoms, while more severe variants can be linked to developmental delay, tremor, or other neurologic problems.
Treatment
What does that mean for your treatment
Pathogenic variants in the MAT1A gene can make treatment focus on lowering methionine levels, often with a methionine-restricted diet when blood levels are high or symptoms are present. S-adenosylmethionine, or SAMe, may help some people, especially when neurologic symptoms suggest low SAMe in the body.
Conditions associated with MAT1A
Gene function
What if the gene works
In adults, the MAT1A gene is most active in the liver. It helps liver cells make SAMe, a small molecule that supports many everyday cell jobs. This central MAT1A gene function in the liver keeps methionine handling organized and helps routine cell chemistry run smoothly.
The MAT1A gene gives liver cells instructions to make SAMe from methionine. When this step runs normally, cells have a steady supply of a molecule used in many basic reactions.
By turning methionine into SAMe, this gene helps the liver process methionine from food. That supports the methionine cycle, a routine pathway your body uses to handle this protein building block.
SAMe made through MAT1A donates methyl groups, small chemical tags that help cells control normal activity. These tags are used on DNA, proteins, and fats as part of everyday cell upkeep.
SAMe from MAT1A also feeds pathways that make other useful cell molecules, including some needed for membrane upkeep and normal cell growth. This helps liver cells carry out steady day to day work.
What is a variant?
A genetic variant is a small difference in the DNA sequence of a gene. These changes are common and help account for normal human diversity, such as differences in appearance, metabolism, or the way the body responds to environmental influences. Many variants do not have any noticeable effect and simply represent 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
Many MAT1A gene variants change the shape, stability, or assembly of the liver enzyme that makes S-adenosylmethionine, a key cell compound, so the protein works less well or not at all. In practice, how MAT1A gene variants affect enzyme activity ranges from mild partial loss to near-complete loss. More disruptive variants often lead to a larger drop in enzyme function, which can raise methionine more and make related features more likely to appear earlier.
How variants are linked to conditions
Pathogenic variants in the MAT1A gene cause methionine adenosyltransferase I/III deficiency, a condition linked to persistent hypermethioninemia on newborn screening or later blood tests. Many people carrying one MAT1A variant have isolated high methionine levels and no symptoms. People with two disease causing variants are more likely to have much higher levels and may develop neurologic features, so a confirmed MAT1A-related diagnosis reflects an established genetic condition rather than a general risk marker.
A variant is not necessarily a diagnosis
Gene variants are a normal feature of human biology and are common throughout the general population. Most have no direct effect on health and simply reflect natural human diversity. For many genes, carrying a variant associated with a condition indicates a possible link rather than a definite diagnosis, especially when more than one gene and environmental factors are involved. In some situations, though, a single well-characterized variant in a particular gene is enough to confirm a diagnosis.
Are there things that can increase or change my risk?
For MAT1A, risk is mainly shaped by the genetic change itself and whether it is inherited from one or both parents. Some changes cause only high methionine levels on blood tests, while others are more likely to affect the brain or liver. There is not enough evidence to say that lifestyle factors meaningfully change the chance of having a MAT1A-related condition.
Inheritance of MAT1A variants
For families trying to understand MAT1A gene inheritance, the pattern can differ depending on the specific MAT1A-related condition and variant. Most symptomatic MAT1A-related methionine adenosyltransferase deficiency follows an autosomal recessive pattern, which means a child inherits one altered copy of the MAT1A gene from each parent. Some MAT1A variants linked to milder, isolated high methionine levels in the blood are inherited in an autosomal dominant pattern, so a parent with the variant can pass it to a child with a 50% chance in each pregnancy. Because the MAT1A gene is on chromosome 10, it is inherited equally by people of any sex.
What does my MAT1A result mean for my family?
For MAT1A, what this means for family members depends on the kind of result. Some MAT1A changes are passed down in a recessive pattern, which can mean brothers, sisters, and future children could be affected or be carriers; other MAT1A changes act in a dominant pattern, so close relatives may also carry the change. Because MAT1A is linked to more than one inheritance pattern, family implications are best interpreted in the context of the exact result.
Genetic information
Genetic testing
How you find out about variants
MAT1A genetic testing uses a blood or saliva sample to look for variants in the MAT1A gene. Labs usually read the gene’s DNA sequence and may confirm a finding with a second method. Results can show whether no variant, one variant, or two variants were found.
When should I consider getting a genetic test?
Consider testing for changes in the MAT1A gene if a newborn screen or blood test shows high methionine, an amino acid in the blood, or if this condition runs in your family. Testing can help confirm the cause and clarify whether other relatives may also carry it.
A genetic result is only one part of your health story
Genetic test results can provide useful insight, yet what they can tell you varies with the condition and the kind of variant involved. Many factors, including lifestyle, environment, age, and medical history, influence how the body functions over time. For some conditions, particularly those shaped by many genes, genetic information offers context rather than certainty and makes the most sense when considered with other parts of care. In other situations, a genetic result can give a clear answer. In areas like medication response, these results can also help put personal experiences in context.
Pharmacogenetics
How variants shape your response to medicine
Genetic variation can affect how people respond to medicines. Some people break down or move a drug through the body differently, so the same dose may work better for one person, have less effect in another, or cause more side effects in someone else. These differences are common and can influence both how well a treatment works and how sensitive a person is to it.
What is Pharmacogenetics?
Pharmacogenetics examines how differences in genes can affect the way a person responds to medication. By looking at links between genes and drugs, it helps 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 processes it. This information can support treatment decisions that are better informed and more individualized. You can read more about this topic in the LearnHub.
Drugs influenced by the MAT1A gene
When should I seek medical advice?
There is not yet a broadly confirmed role for this gene in guiding medication choice or dose. Questions about medicines, side effects, or your overall health are best discussed with your doctor or pharmacist.
History
Research on the MAT1A gene grew out of mid 20th century studies of liver chemistry, when scientists were trying to map how the body handles the amino acid methionine. Initially understood only through visible traits, later recognized as tied to a specific gene, this work became clearer as researchers separated liver specific methionine adenosyltransferase from related forms found in other tissues. In the 1990s, the MAT1A gene was cloned and its link to inherited hypermethioninemia became established. From these first observations, research expanded steadily. Genetic studies then showed that different MAT1A variants could explain why some people found through newborn screening had high methionine levels, while others remained well for many years. This history helped move MAT1A from a laboratory finding into routine clinical genetics.