The TMEM126B gene helps mitochondria, the parts of cells that make energy, build a key energy making unit called complex I. When this gene does not work properly, cells may produce less energy, especially in tissues with high needs such as muscles and the heart. People with harmful variants in the TMEM126B gene can develop a mitochondrial condition with muscle weakness, low stamina, and sometimes heart or nerve related problems. Many variants are harmless, while a few may change how the gene works.
What is a gene?
Genes are stretches of DNA that give your cells instructions for making molecules or directing activities in the body. Some carry the code for proteins, which do much of the cell’s work. Others mainly regulate when certain processes happen, where they happen, and how active they are. Taken together, genes affect how the body develops and functions, and they can also influence how you respond to food, stress, or medications. For a deeper look at this topic, you can find more in the LearnHub.
Overview
TMEM126BGene function
What if the gene works
The TMEM126B gene helps assemble complex I, a key part of mitochondria, your cells’ energy centers. This supports how cells make ATP, the energy they use every day.
Risk
What if the gene does not work
When both copies of the TMEM126B gene do not work well, people can develop mitochondrial disease with muscle weakness, exercise intolerance, and sometimes heart or breathing problems. Milder or more severe variants may influence symptom onset and severity.
Treatment
What does that mean for your treatment
For people with a pathogenic or loss-of-function variant in the TMEM126B gene, no TMEM126B-specific treatment or management approach is currently established.
Conditions associated with TMEM126B
Gene function
What if the gene works
Your cells need a steady way to make energy all day. Inside mitochondria, the TMEM126B gene helps put together one of the main energy-making machines. When this process runs smoothly, cells can turn nutrients into usable energy for routine body functions.
The TMEM126B gene helps assemble complex I, a large protein group inside mitochondria. It supports the joining of several parts so this energy-making system is built correctly.
Once complex I is in place, mitochondria can pass energy along their internal chain in a controlled way. This helps your cells convert nutrients into ATP, the main form of usable cellular energy.
This role supports a steady energy supply for routine tasks across the body. It helps explain how the TMEM126B gene helps cells make energy for movement, signaling, and other everyday work.
What is a variant?
A genetic variant is a small difference in the DNA sequence of a gene. These differences are common and help make each person genetically unique, including in traits such as appearance, metabolism, or the way the body responds to environmental influences. Many variants do not have any noticeable effect and are simply part of normal 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
TMEM126B gene variants often make the TMEM126B protein unstable, shortened, or less able to join the protein group that assembles mitochondrial complex I, the cell’s energy making machinery. This can leave complex I only partly built and reduce its activity. Milder variants may leave some function in place, while more severe loss-of-function variants can remove most function and are linked to earlier or more pronounced features of TMEM126B-related mitochondrial disease.
How variants are linked to conditions
Pathogenic variants in the TMEM126B gene cause a rare inherited mitochondrial disease called complex I deficiency. People with this condition may have exercise intolerance, muscle weakness, fatigue, and sometimes heart involvement such as cardiomyopathy. In medical genetics, TMEM126B gene variants linked to conditions are mainly tied to this diagnosis rather than to a broad range of common diseases.
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 reflect the natural diversity seen among people. In many genes, having a variant connected with a condition points to a possible association, not a definite diagnosis, particularly when several genes and environmental influences also play a role. In some situations, though, one well-characterized variant in a particular 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 risk related to the TMEM126B gene. For many living with a TMEM126B change, the main factor is the exact genetic change itself rather than lifestyle or environmental exposures. Anyone with concerns about personal or family risk should speak with a doctor or genetic counselor.
Inheritance of TMEM126B variants
Variants in the TMEM126B gene are inherited in an autosomal recessive pattern. This means a person usually develops a TMEM126B-related condition only when they inherit two disease-causing variants in the TMEM126B gene, one from each parent. Parents who each carry one variant are typically unaffected carriers, and with each pregnancy they have a 25% chance of having an affected child, a 50% chance of having a carrier child, and a 25% chance of having a child without either variant. TMEM126B inheritance is the same for males and females.
What does my TMEM126B result mean for my family?
TMEM126B-related illness is usually passed down in a recessive pattern, so close relatives may also carry the gene change even if they feel well. Brothers and sisters can have a chance of having the same condition or of being carriers, while parents are often carriers. Children of someone with a TMEM126B-related condition will usually be carriers unless the other parent also carries a TMEM126B change.
Genetic information
Genetic testing
How you find out about variants
To look for changes in the TMEM126B gene, doctors use TMEM126B genetic testing with a blood or saliva sample. A lab reads the gene's DNA code and checks for variants that may help explain symptoms or confirm a suspected inherited condition.
When should I consider getting a genetic test?
Consider testing for changes in the TMEM126B gene if you or your child has signs of a rare inherited problem with how cells make energy, such as early muscle weakness, getting very tired with activity, or unexplained heart muscle disease. Testing can also help when a close relative has a known TMEM126B variant.
A genetic result is only one part of your health story
A genetic result can provide useful insight, but how much it reveals varies with the condition and the type of variant involved. Over time, many factors, including lifestyle, environment, age, and medical history, affect how the body functions. For some conditions, especially those shaped 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 such as medication response, genetic results can also help make sense of individual experiences.
Pharmacogenetics
How variants shape your response to medicine
Genetic variation can affect how your body responds to medicines. Some people break down a drug more slowly or more quickly, so the same dose can lead to different effects from one person to another. This is a common reason why a treatment may work well for one person but less well for someone else, or why side effects may be more noticeable. In some cases, inherited differences in how the body handles medicines can influence both how well a drug works and how sensitive a person is to it.
What is Pharmacogenetics?
Pharmacogenetics examines how differences in a person’s genes affect the way they respond to medicines. By studying links between genes and medications, it helps explain why the same treatment can work differently in different people. For many drugs, genes can influence how the body handles a medicine or how strong its effects are. This information can support treatment choices that are more informed and more individualized. More detail on this topic is available in the LearnHub.
Drugs influenced by the TMEM126B gene
When should I seek medical advice?
There is not yet a broadly confirmed role for this gene in how the body responds to medicines, so medication concerns, side effects, or new symptoms are best discussed with your doctor.
History
TMEM126B entered the medical literature in the 2010s, during a period when researchers were identifying genes involved in mitochondrial disease. It was first recognized through studies of how cells build complex I, a key part of the body’s energy system. From these first observations, research expanded steadily. Soon after, inherited variants in the TMEM126B gene were linked to families with features of mitochondrial disease, helping confirm its clinical importance. Over time, descriptions became more precise as genetic testing connected TMEM126B variants with a clearer pattern of symptoms. Its history is mainly a scientific one, shaped by modern sequencing and growing understanding of rare inherited conditions.