The FASN gene gives your cells instructions to make fatty acids, a basic type of fat used to build cell membranes and store energy. If it does not work well, cells may struggle to make enough of these fats, which can affect growth, energy balance, and normal cell function. This gene helps your body turn extra food energy into fat for later use. In medicine, the FASN gene is often studied in cancer and metabolic research because some cells become unusually dependent on it.
What is a gene?
Genes are sections of DNA that give your cells instructions for making molecules or directing processes in the body. Some genes carry the information needed to make proteins, the parts of cells that do much of the work. Other genes mainly regulate when certain processes happen, where they take place, and how strongly they run. Together, genes shape how the body develops and functions, and they can influence how you respond to food, stress, or medications. To explore this topic further, you can learn more in LearnHub.
Overview
FASNGene function
What if the gene works
The FASN gene helps your cells make fatty acids, which are building blocks for cell membranes and stored energy. This supports normal growth, tissue upkeep, and everyday cell function.
Risk
What if the gene does not work
More disruptive variants in the FASN gene can cause a rare condition affecting brain growth and development, often with developmental delay, feeding problems, and short stature. Milder variants may lead to fewer or later appearing features.
Treatment
What does that mean for your treatment
No treatment plan is currently tailored to pathogenic or loss-of-function variants in the FASN gene. The FASN gene is being studied as a drug target in some cancers and in metabolic research, but this has not led to guideline based treatment for inherited FASN variants.
Gene function
What if the gene works
Your body needs a steady supply of fats for cell membranes, energy storage, and normal cell activity. The FASN gene gives cells instructions for a protein that builds certain fats from smaller parts. This helps explain what the FASN gene does in the body each day.
Inside your cells, the FASN gene helps make a common fatty acid called palmitate from smaller chemical pieces. Cells can then use palmitate as a starting material to build other fats they need.
Fats made with help from the FASN gene become building blocks for cell membranes, the thin layers around cells. This supports routine cell upkeep and gives growing cells material for new membranes.
Some of these fats can be converted into forms your body stores for later energy use. They also serve as raw material for other everyday fats used across many tissues.
What is a variant?
A genetic variant is a minor difference in the DNA sequence within a gene. These differences are common and help shape normal human diversity, including variation in appearance, metabolism, and the way the body responds to environmental influences. Many variants do not have any noticeable effect and are simply part of natural genetic variation. At times, though, a variant changes how a gene works to a greater degree and may contribute to or cause a genetic condition.
Genetic variants
What if the gene does not work
Variants in the FASN gene can change how fatty acid synthase is built, folded, or assembled, which helps explain how FASN gene variants affect enzyme activity in cells. Milder variants may leave some activity in place, while more severe variants can sharply reduce activity, destabilize the protein, or lead to a shortened protein that is cleared away. This can lower the cell’s ability to make key fatty acids and alter membrane and lipid storage processes.
How variants are linked to conditions
At present, the FASN gene does not yet have a broadly confirmed link to a specific health condition, so information about health conditions linked to FASN gene variants is still developing. Anyone with a confirmed diagnosis involving the FASN gene should follow advice from their doctor or genetic counselor, because care is based on the exact variant and the person’s symptoms.
A variant is not necessarily a diagnosis
Variants in genes are a usual part of human biology and are common across the general population. Most do not have a direct effect on health and instead are part of 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 play a role. In some situations, though, one well-characterized variant in a particular gene may be 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 risk related to FASN itself. Many health outcomes linked in research to FASN are shaped by a mix of genes, body weight, diet, hormone signals, and other health conditions, so personal risk is not determined by this gene alone.
Inheritance of FASN variants
For families trying to understand how FASN gene variants are inherited, there is not yet a broadly confirmed disease specific inheritance pattern tied to the FASN gene. As research develops, this may become clearer for particular health conditions. The FASN gene is located on chromosome 17, which is an autosome, so each person inherits one copy from each parent. In general, changes in genes on autosomes can be passed down through either side of the family.
What does my FASN result mean for my family?
There isn't yet a broadly confirmed inheritance pattern tied to a specific condition for FASN, though this understanding can change as research develops. If you have a specific FASN result and questions about what it could mean for your family, a doctor or genetic counselor can explain how it may or may not be relevant for close relatives.
Genetic information
Genetic testing
How you find out about variants
Genetic testing for FASN variants looks at DNA from a blood sample or saliva to see whether you carry a change in the FASN gene. Labs usually read the gene's code with sequencing and compare it with a reference sequence, which can confirm a specific variant when one is present.
When should I consider getting a genetic test?
There isn't yet a broadly established, FASN-specific clinical reason for genetic testing. Decisions about testing are usually based on your personal health history, family history, and the broader question your doctor or genetic counselor is trying to answer.
A genetic result is only one part of your health story
A genetic finding can provide useful insight, but how much it reveals depends on the condition and the type of variant involved. Many factors, including lifestyle, environment, age, and medical history, also shape how the body works over time. In some conditions, especially those influenced by many genes, genetic information provides context rather than certainty and is most helpful 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 put individual experiences into context.
Pharmacogenetics
How variants shape your response to medicine
Genetic variation can affect how people respond to medicines. Inherited differences can change how the body absorbs, breaks down, transports, or responds to a drug. These common differences may influence how well a treatment works or how likely someone is to notice side effects, which helps explain why the same medicine can feel too strong, too weak, or just right in different people.
What is Pharmacogenetics?
Pharmacogenetics examines how differences in a person’s genes can affect the way medications work. It studies gene-drug patterns to help explain why the same treatment may not have the same effect in everyone. With many medicines, genes can influence how much effect a drug has or how the body handles it. This information can support better informed, more individualized treatment choices. More detailed information on this topic is available in the LearnHub.
Drugs influenced by the FASN gene
When should I seek medical advice?
There is not yet a broadly confirmed role for this gene in predicting medication response, so questions about medicines, side effects, or new health changes are best discussed with your doctor or pharmacist.
History
Research on the FASN gene grew out of mid-20th-century work on how the body makes fats, when scientists first isolated the large fatty acid synthase enzyme from animal tissues. Initially understood only through visible traits, later recognized as tied to a specific gene, this work helped connect classic biochemistry with modern genetics. By the 1980s and 1990s, researchers had identified and mapped the human FASN gene, which made it easier to study how its activity changes in different tissues. Interest widened when cancer studies found unusually high FASN activity in some tumors, bringing the gene into a broader medical spotlight. From these first observations, research expanded steadily, linking FASN to metabolism, nutrition, and cancer biology. Today, its history reflects a larger shift from studying enzymes alone to understanding the genes behind them.