The TWNK gene helps maintain the DNA inside mitochondria, the parts of cells that make energy for the body. When the TWNK gene does not work properly, cells may struggle to produce enough energy, which can lead to drooping eyelids, trouble moving the eyes, muscle weakness, balance problems, nerve symptoms, or, in some children, liver disease. This gene plays an important role in parts of the body that need a steady supply of energy, especially muscles, nerves, and the brain.
What is a gene?
A gene is a stretch of DNA that carries instructions your cells use to make molecules or regulate activities in the body. Some genes contain the directions for making proteins, which do much of the work inside cells. Other genes mainly help determine when certain processes happen, where they happen, and how active they are. Together, genes affect how the body develops and works, and they can influence how you respond to food, stress, or medications. If you want to explore this topic more deeply, you can learn more in the LearnHub.
Overview
TWNKGene function
What if the gene works
The TWNK gene helps cells copy and maintain mitochondrial DNA, the small set of DNA inside mitochondria. This supports normal energy production, especially in tissues with high energy needs like muscles and nerves.
Risk
What if the gene does not work
Variants in the TWNK gene can disrupt mitochondrial DNA maintenance. Milder variants often cause drooping eyelids and trouble moving the eyes, while more severe variants may lead to early onset nerve and muscle problems, balance problems, seizures, or liver disease.
Treatment
What does that mean for your treatment
No TWNK-specific treatment or drug choice is currently established for pathogenic variants in the TWNK gene, so care is guided by a person’s symptoms and the organs involved rather than by a gene-directed therapy.
Conditions associated with TWNK
Gene function
What if the gene works
Your cells rely on the TWNK gene to help mitochondria, the parts of cells that make energy, manage their own DNA. Inside mitochondria, this gene supports the copying and steady upkeep of mitochondrial DNA. That helps cells keep the genetic instructions needed for day to day energy production.
The TWNK gene helps unwind mitochondrial DNA so it can be copied. Its protein works like a small motor, separating the two DNA strands so the cell’s copying tools can move along them.
Inside mitochondria, the TWNK gene supports mitochondrial DNA replication and maintenance. By helping new DNA copies form in an orderly way, it helps cells keep a steady supply of the instructions mitochondria use for energy production.
What is a variant?
A genetic variant is a small difference in the DNA sequence within a gene. These changes are common and help account for normal human diversity, including differences in appearance, metabolism, or how the body responds to environmental influences. Many variants have no noticeable effect and are simply part of natural genetic variation. In some situations, though, a variant can more substantially change how a gene functions and may contribute to or cause a genetic condition.
Genetic variants
What if the gene does not work
Variants in the TWNK gene can weaken the cell’s mitochondrial DNA copying machinery by changing the helicase protein’s shape, stability, or ability to bind and unwind DNA. Some mainly reduce activity, while more disruptive variants can block assembly of the working protein complex or sharply limit mitochondrial DNA maintenance. This spectrum helps explain how TWNK gene variants affect mitochondrial DNA replication, from later-onset, often milder mitochondrial disease to earlier, more severe forms.
How variants are linked to conditions
Pathogenic variants in the TWNK gene can cause inherited mitochondrial conditions, most often progressive external ophthalmoplegia, which may bring drooping eyelids and gradually limited eye movements. Established links between TWNK gene variants and mitochondrial disease also include infantile-onset spinocerebellar ataxia, a childhood condition that can affect balance, nerves, muscle strength, and development. Some people with TWNK-related conditions also have hearing loss and, in some women, ovarian insufficiency.
A variant is not necessarily a diagnosis
Variants in genes are a normal part of human biology and are common throughout the general population. Most do not have a direct effect on health and instead represent natural human diversity. For many genes, carrying a variant associated with a condition suggests a possible link rather than a definite diagnosis, especially when several genes and environmental factors also play a part. In some situations, however, a single well-characterized variant in a specific gene is enough to confirm a diagnosis.
Are there things that can increase or change my risk?
For TWNK-related conditions, risk is mostly shaped by the specific gene change and whether it is inherited from one parent or both, rather than by lifestyle or everyday exposures. There is not enough evidence to say that diet, exercise, or other routine changes lower the chance of developing a TWNK-related condition, though regular follow-up can help spot problems early.
Inheritance of TWNK variants
TWNK-related conditions can follow more than one inheritance pattern, so TWNK gene inheritance depends on the specific condition and variant. Some TWNK gene variants are inherited in an autosomal dominant way, which means a parent carrying the variant can pass it to a child with a 50% chance in each pregnancy. Other variants in the TWNK gene are inherited in an autosomal recessive way, which means a child usually inherits one nonworking copy from each parent. In recessive families, parents are often healthy carriers, and each pregnancy has a 25% chance of the child inheriting both altered copies.
What does my TWNK result mean for my family?
TWNK can affect families in more than one way, because different changes in this gene are linked to different inherited conditions. In some families, a TWNK result means close relatives such as a parent, brother, sister, or child could also carry the same change and may consider testing. In others, parents may be healthy carriers, and brothers or sisters could also be carriers or be affected. What it means for your family depends on the exact TWNK result and the condition involved.
Genetic information
Genetic testing
How you find out about variants
You find out about variants in the TWNK gene through genetic testing, usually using a blood sample or cheek swab sent to a lab. TWNK genetic testing may be part of a mitochondrial disease panel, whole exome sequencing, or whole genome sequencing. Results can identify a variant linked to disease, a benign variant, or a variant of uncertain significance.
When should I consider getting a genetic test?
Consider TWNK genetic testing if you or your child has unexplained drooping eyelids, trouble moving the eyes, muscle weakness, balance problems, or other signs of a mitochondrial condition, especially when these run in the family. Testing may also be considered after muscle, nerve, or brain findings suggest a TWNK-related condition.
A genetic result is only one part of your health story
A genetic result can be informative, but how much it explains depends on the condition and on the specific type of variant. Over time, the way the body functions is shaped by many factors, including lifestyle, environment, age, and medical history. For some conditions, particularly those affected by many genes, genetic information provides context rather than certainty and makes the most sense when considered with 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 personal experiences into context.
Pharmacogenetics
How variants shape your response to medicine
Genetic variation can affect how your body handles medicines. Some people process a drug more slowly or more quickly, while others may be more or less sensitive to its effects. This helps explain why the same treatment works well for one person, seems weaker for another, or causes more side effects in someone else. These differences are common and are one part of the bigger picture, along with age, other health conditions, and other medicines.
What is Pharmacogenetics?
Pharmacogenetics examines how genetic differences can shape a person’s response to medication. It focuses on connections between genes and drugs to help explain why the same treatment may work differently from one person to another. For many medicines, genes affect either how strongly a drug works or how the body processes it. This understanding 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 TWNK gene
When should I seek medical advice?
There is not yet a broadly confirmed role for this gene in guiding medication choice or dose. If you have concerns about side effects, new symptoms, or how your medicines fit with your overall health, it is a good idea to speak with your doctor or pharmacist.
History
The TWNK gene entered medical genetics in the early 2000s, when researchers linked variants in this gene to inherited forms of progressive external ophthalmoplegia, a condition that can affect eye movement. It was first reported under the name C10orf2 and later became more widely known as TWNK. Initially understood only through visible traits, later recognized as tied to a specific gene, this work helped connect certain family patterns of muscle weakness with changes in mitochondrial DNA maintenance. From these first observations, research expanded steadily. Studies in families from different countries showed that both dominant and recessive inherited patterns could involve the TWNK gene, which broadened clinicians’ understanding of mitochondrial conditions and helped shape modern genetic classification.