The SMO gene helps pass growth signals between cells, especially during early development. This gene plays an important role in shaping the brain, face, bones, skin, and other tissues. If the SMO gene does not work properly, development can be disrupted, and some people may have a rare condition such as Curry-Jones syndrome. Certain activating variants make the signal too strong instead of too weak and are linked to some cancers, including basal cell carcinoma.
What is a gene?
A gene is a stretch of DNA that gives your cells instructions to make molecules or regulate processes in the body. Some genes carry the code for proteins, which do much of the work inside cells. Others mainly help determine when certain processes happen, where they take place, and how strongly they are carried out. Together, genes affect how the body develops and works, and they can also influence how you respond to food, stress, or medications. You can find more on this topic in the LearnHub.
Overview
SMOGene function
What if the gene works
The SMO gene helps cells respond to growth signals that guide development. It supports how tissues form before birth and helps some cells renew and repair tissues later in life.
Risk
What if the gene does not work
Variants in the SMO gene can disturb early development, causing Curry-Jones syndrome with changes in the face, skin, fingers or toes, and gut. Effects may be milder or more severe, and overactive SMO signaling is also linked to some cancers.
Treatment
What does that mean for your treatment
No SMO-specific treatment or management approach is currently established based on carrying a pathogenic SMO variant. The SMO gene is a drug target, and medicines that block SMO, such as vismodegib and sonidegib, are used in some cancers linked to the Hedgehog pathway, although response can vary with the tumor and the exact variant.
Conditions associated with SMO
Gene function
What if the gene works
Cells use the SMO gene to pass along growth and development messages. It is a central part of Hedgehog signaling, a communication system that helps organize the body during early development and supports cell renewal later in life. Understanding how the SMO gene works in the Hedgehog pathway helps explain how cells coordinate timing, position, and identity.
The SMO gene helps carry Hedgehog messages from the cell surface to the cell’s control center. Its protein becomes active when a Hedgehog signal is present and moves the message forward.
This pathway uses the SMO protein to influence GLI proteins (gene-control proteins). That helps cells turn the right genetic programs on or off at the right time.
During early development, SMO signaling helps cells sense location cues and choose the right role. This supports the planned formation of structures such as the brain, face, spine, and limbs.
In some adult tissues, this signaling pathway helps guide measured cell replacement and repair. It supports routine upkeep in places where cells need to be renewed over time.
What is a variant?
Genetic variants are small differences in a gene’s DNA sequence. These changes are common and are part of normal human diversity, including differences in appearance, metabolism, and the way the body responds to environmental influences. Many variants do not cause any noticeable effects and simply represent natural genetic variation. In some cases, though, a variant can change how a gene functions more significantly and may contribute to or cause a genetic condition.
Genetic variants
What if the gene does not work
SMO gene variants can either keep the protein switched on when it should be quiet or make it signal less effectively. In plain terms, what happens if the SMO gene does not work depends on the variant: milder changes may partly reduce signaling, while more severe variants can disrupt the protein’s shape, stability, or movement to the cell’s signaling hub. Variants that overactivate SMO are linked to Curry-Jones syndrome, while stronger loss of function may have broader effects on early development.
How variants are linked to conditions
Pathogenic variants in the SMO gene can cause Curry-Jones syndrome, a rare condition that may affect the skin, fingers or toes, brain, and digestive tract. Separately, acquired SMO gene variants linked to cancer have been found in some basal cell carcinomas and medulloblastomas. These tumor variants arise in cells during life and are not the same as an inherited change in the SMO gene.
A variant is not necessarily a diagnosis
Genetic variants are a routine part of human biology and are found commonly across the population. Most do not have a direct effect on health and instead reflect the normal diversity seen among people. For many genes, having a variant tied to a condition suggests a possible association, not a firm diagnosis, especially when more than one gene and environmental factors play a role. In some instances, however, one well-characterized variant in a specific gene can 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 everyday factors that increase or lower risk related to the SMO gene itself. Risk can depend more on the exact gene change and whether it is inherited or happens only in certain body cells, so personal guidance from a doctor or genetic counselor can help put results in context.
Inheritance of SMO variants
For SMO-related conditions, there is not one broadly established family inheritance pattern in the usual Mendelian sense. In practice, how SMO gene variants are inherited depends on the condition, and the best-known SMO-related condition, Curry-Jones syndrome, most often happens because of a new mosaic variant that arises after conception rather than being passed down from a parent. This means the variant is present in only some of the body's cells, which can make inheritance within a family uncommon. The SMO gene is located on chromosome 7, an autosome, so each person has two copies of this gene as part of the set inherited from both parents.
What does my SMO result mean for my family?
There is not yet a broadly confirmed inherited pattern for SMO that applies in a simple, family-wide way. Some SMO-related conditions are linked to changes that happen new in the affected person, rather than being passed down through a family. If you have a specific SMO result and want to understand what it could mean for relatives, a genetics specialist can explain it in the context of that exact finding.
Genetic information
Genetic testing
How you find out about variants
To find variants in the SMO gene, doctors use genetic testing on a blood sample, saliva, or sometimes tumor tissue. SMO gene genetic testing reads the gene’s DNA code and looks for changes that may help explain an inherited condition or guide cancer care.
When should I consider getting a genetic test?
Genetic testing for the SMO gene may be considered if a child has signs of the very rare Curry-Jones syndrome, such as unusual skin, finger or toe, and brain or gut changes. SMO may also be checked in tumor testing for some cancers, especially basal cell skin cancer or some brain tumors, because results can affect treatment.
A genetic result is only one part of your health story
A genetic result can be quite informative, but how much it shows depends on the condition and on the specific type of variant. Many factors, including lifestyle, environment, age, and medical history, influence how the body functions over time. With some conditions, especially those shaped by many genes, genetic information provides context rather than certainty and is most useful when viewed together with other parts of care. In other situations, a genetic result can offer a clear answer. In areas like medication response, genetic results may also help put a person’s experience into context.
Pharmacogenetics
How variants shape your response to medicine
Genetic variation can affect how people respond to medicines. Small differences in genes can change how the body breaks down a drug, moves it through the body, or how strongly the drug acts on its target. 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. These differences are common and are only one part of the picture, along with age, other health conditions, and other medicines.
What is Pharmacogenetics?
Pharmacogenetics examines how differences in genes can affect the way a person responds to medications. It studies gene drug patterns to help explain why the same treatment may work differently from one person to another. For many drugs, genes influence both how strongly a medicine works and how the body handles it. This information can support more informed, individualized treatment decisions. More on this topic is available in the LearnHub.
Drugs influenced by the SMO gene
When should I seek medical advice?
There is not yet a widely confirmed role for this gene in routine medication decisions, so questions about medicines, side effects, or treatment changes are best discussed with your doctor. SMO has mainly been studied in cancer care, where changes in the SMO gene within a tumor can affect how some targeted treatments work.
History
Research on the SMO gene grew out of work on the hedgehog pathway in fruit flies during the late 20th century, when scientists were mapping genes that guide early development. Building on this early work, scientists uncovered more about the gene as closely related pathways were identified in people and linked to inherited conditions and some cancers. Interest widened when studies of cyclopamine, a plant chemical known for causing birth differences in livestock, helped reveal how SMO could be blocked. That discovery later shaped the development of targeted cancer medicines aimed at this pathway. Over time, descriptions became more precise. Today, the SMO gene is recognized as an important part of the broader history of developmental genetics and targeted therapy.