The TAT gene helps the liver break down tyrosine, a building block from food and body proteins. If it does not work properly, tyrosine can build up and cause tyrosinemia type II. People with this inherited condition may develop painful, light-sensitive eyes, thickened skin on the palms and soles, and sometimes learning or developmental challenges. Genetic results in the TAT gene help confirm the diagnosis.
What is a gene?
Genes are stretches of DNA that hold instructions your cells use to make molecules or regulate activities in the body. Some genes provide the information needed to produce proteins, which are the parts of cells that do much of the work. Other genes mainly control when certain processes happen, where they take place, and how strongly they are carried out. Together, genes affect how the body develops and functions, and they can influence how you respond to food, stress, or medications. For a deeper look at this topic, you can find more in the LearnHub.
Overview
TATGene function
What if the gene works
The TAT gene helps the liver break down tyrosine, an amino acid from food and body proteins. This supports normal amino acid balance and helps prevent tyrosine from building up.
Risk
What if the gene does not work
Variants in the TAT gene can impair tyrosine breakdown and cause tyrosinemia type II. Milder to more severe variants may lead to painful eye changes, thickened skin on the palms and soles, and sometimes learning difficulties.
Treatment
What does that mean for your treatment
Pathogenic variants in the TAT gene usually guide treatment toward lowering tyrosine levels with a diet low in tyrosine and phenylalanine, often with a specialized medical formula. No drug treatment specific to the TAT gene is currently established, so care mainly focuses on dietary management.
Conditions associated with TAT
Gene function
What if the gene works
In the liver, the TAT gene helps your body handle tyrosine, a building block from protein in food. This is part of normal amino acid metabolism, which means processing and reusing amino acids from meals. Understanding TAT gene function in the body helps show how the liver manages nutrients day to day.
The TAT gene helps liver cells begin breaking down tyrosine, an amino acid found in many protein-rich foods. It changes tyrosine into the next substance in a pathway your body uses to process nutrients.
By handling tyrosine after meals, this gene helps keep amino acid levels in balance. That supports normal daily body chemistry as protein from food is used, stored, and cleared.
TAT is most active in the liver, where much of your amino acid processing happens. Its protein helps link tyrosine breakdown to other steps your body uses for energy and routine cell work.
What is a variant?
A genetic variant is a minor change in the DNA sequence of a gene. These changes are common and help explain normal differences between people, such as appearance, metabolism, or 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 TAT gene can make the tyrosine aminotransferase enzyme unstable, less active, or absent, so cells break down tyrosine less effectively. Some TAT gene variant effects are mild and leave part of the enzyme working, while more disruptive changes can shorten the enzyme or stop the cell from making it properly. This range of loss can influence the degree of enzyme deficiency and, in tyrosinemia type II, may affect how early features appear and how pronounced they are.
How variants are linked to conditions
Pathogenic variants in the TAT gene cause tyrosinemia type II, a rare inherited condition also called Richner-Hanhart syndrome. TAT gene variants are linked to eye problems such as pain, tearing, and sensitivity to light, along with thickened skin on the palms and soles. Some people also have developmental or learning difficulties. When a person inherits disease-causing variants in both copies of the TAT gene, the genetic finding can confirm the diagnosis.
A variant is not necessarily a diagnosis
Genetic variants are a usual part of human biology and are common throughout the general population. Most do not directly affect health and instead reflect natural human diversity. For many genes, carrying a variant associated with a condition points to a possible link rather than a confirmed diagnosis, especially when several genes and environmental factors play a role. In some situations, though, a single well-characterized variant in a particular gene can be enough to confirm a diagnosis.
Are there things that can increase or change my risk?
For TAT, the main risk is inherited: the condition usually happens when both copies of the gene have disease-causing changes. In people living with TAT-related tyrosinemia, higher tyrosine levels, often linked to protein intake, can worsen eye, skin, and learning problems. Diet changes can help control symptoms and lower complications, but they do not remove the genetic cause.
Inheritance of TAT variants
TAT gene inheritance for tyrosinemia type II follows an autosomal recessive pattern. This means a child usually inherits one altered copy of the TAT gene from each parent, and the parents are often healthy carriers. When both parents carry a variant in the TAT gene, each pregnancy has a 25% chance of being affected, a 50% chance of resulting in a carrier child, and a 25% chance of resulting in a child without the family variant. Because TAT is not on a sex chromosome, this inheritance pattern is the same for boys and girls.
What does my TAT result mean for my family?
For families with a disease-causing TAT result, close relatives may also be carriers, even if they have no symptoms. Brothers and sisters could be affected or could carry the same gene change, and future children in the family may also be affected if both parents carry a TAT change. This matters most for family planning and for relatives who may want to learn their own carrier status.
Genetic information
Genetic testing
How you find out about variants
Testing for variants in the TAT gene usually uses a blood or saliva sample. This explains how genetic testing finds TAT gene variants: a lab reads the gene’s DNA sequence and checks for changes that may help confirm a diagnosis, clarify carrier status, or support family testing.
When should I consider getting a genetic test?
Genetic testing for the TAT gene may be worth considering if high tyrosine levels are found along with painful eye irritation, light sensitivity, or thick painful skin on the palms and soles, which can point to tyrosinemia type 2. It can also help when this condition runs in the family or when a child has developmental delays with these symptoms.
A genetic result is only one part of your health story
A genetic result can be informative, yet what it tells you varies depending on the condition and the kind of variant involved. Many factors also shape how the body works over time, including lifestyle, environment, age, and medical history. For some conditions, especially those influenced by many genes, genetic information provides context rather than certainty and is most useful when viewed alongside other parts of care. In other situations, a genetic result may offer a clear answer. In areas like medication response, genetic results can help put individual experiences into context.
Pharmacogenetics
How variants shape your response to medicine
Genetic variation can affect how people respond to medicines. This helps explain why the same treatment works well for one person, has less effect in another, or causes more side effects in someone else. Differences in how the body absorbs, breaks down, transports, or responds to a drug are common, and they can influence both how well a medicine works and how sensitive a person may be to it.
What is Pharmacogenetics?
Pharmacogenetics examines how differences in genes affect the way people respond to medications. It studies connections between genes and drugs to help explain why the same treatment may work differently from one person to another. For many medicines, genes influence how the body processes a drug or how strong its effects are. This information can support more individualized and better informed treatment decisions. More detail on this topic is available in the LearnHub.
Drugs influenced by the TAT gene
When should I seek medical advice?
There is not yet a broadly confirmed role for this gene in guiding how medicines are chosen or adjusted, so any questions about medications, side effects, or new symptoms are best discussed with your doctor.
History
TAT entered medical genetics through studies of a rare inherited condition now called tyrosinemia type II, in which people develop eye, skin, and sometimes learning-related symptoms linked to high tyrosine levels. Initially understood only through visible traits, later recognized as tied to a specific gene, this condition helped connect the TAT gene to the body’s handling of the amino acid tyrosine. As medical science evolved, so did understanding of this gene. Researchers later mapped the TAT gene to chromosome 16 and identified disease-causing variants, which made DNA-based diagnosis possible. These steps shaped today’s understanding of TAT as part of a well-defined metabolic pathway.