The STIL gene helps cells copy key structures they need to divide, which is especially important during early brain growth. If both copies of this gene do not work properly, a baby’s brain and head may grow less than expected before birth, and some children also have short stature or developmental delay. The protein made by this gene helps your cells stay on schedule as they multiply. Variants in the STIL gene are a known cause of some inherited forms of primary microcephaly.
What is a gene?
Genes are sections of DNA that give your cells instructions for making molecules or directing activities in the body. Some genes carry the directions for producing proteins, which are the working parts of cells. Other genes mainly regulate when certain processes take place, where they occur, and how strongly they run. Taken together, genes affect how the body develops and functions, and they can also shape how you respond to food, stress, or medications. To explore this topic in more detail, you can learn more in the LearnHub.
Overview
STILGene function
What if the gene works
The STIL gene helps cells make centrioles, small structures that organize the machinery for cell division. This supports normal cell growth and development, especially in the developing brain.
Risk
What if the gene does not work
When the STIL gene does not work properly, it most often causes a very small head and altered brain development, often with developmental delay. Milder or more severe variants can affect when features begin and how noticeable they are.
Treatment
What does that mean for your treatment
No treatment or management approach that is specific to the STIL gene is currently established for people with pathogenic variants in the STIL gene. In research, STIL is being studied mainly as a cancer biomarker and possible drug target, not as a guide to current treatment.
Conditions associated with STIL
Gene function
What if the gene works
Your cells rely on the STIL gene to copy tiny organizing structures called centrioles before they divide. These structures help set up the machinery that separates genetic material into new cells. Understanding how the STIL gene works makes it easier to see how cells keep division orderly and controlled.
The STIL gene helps each cell build a new centriole at the right time before division. It works with partner proteins to start and shape this tiny organizing structure.
Proper STIL activity helps cells set up the machinery that moves chromosomes into each new cell during division. This supports orderly cell splitting.
STIL activity rises and falls with the cell cycle, the repeating steps a cell follows as it grows and divides. This timing helps centriole copying happen once during each cycle.
Centrioles built with help from the STIL gene help organize microtubules, the fibers that give cells structure and direction. This supports everyday cell shape and internal movement.
What is a variant?
A genetic variant is a minor change in the DNA sequence of a gene. These changes are common and help shape normal differences among people, such as appearance, metabolism, or the way the body responds to environmental influences. Many variants do not have any noticeable effect and simply represent natural genetic variation. Sometimes, though, a variant changes how a gene works more substantially and can contribute to or cause a genetic condition.
Genetic variants
What if the gene does not work
Variants in the STIL gene can change the protein shape, shorten it, or lower how much of it a cell makes, disrupting centriole building during cell division. This explains how STIL gene variants affect cell division: milder missense variants may leave some activity, while more severe variants can greatly reduce or abolish it. Lower activity can make division less reliable, and in conditions linked to the STIL gene, this is associated with earlier or more marked effects on brain growth.
How variants are linked to conditions
Pathogenic variants in the STIL gene cause autosomal recessive primary microcephaly, often called MCPH7, where the head and brain are smaller than expected from before birth. Some people also have developmental delay, learning difficulties, short stature, or brain differences seen on scans. In medical genetics, STIL gene variants are linked to conditions mainly through this diagnosis.
A variant is not necessarily a diagnosis
Genetic variants are a usual part of human biology and are widely found in the general population. Most do not have a direct effect on health and simply reflect natural human variation. For many genes, carrying a variant associated with a condition suggests a possible link rather than a certain diagnosis, especially when several genes and environmental factors are involved. 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 STIL-related inherited conditions, risk mainly changes with family history and whether both biological parents carry a harmful change in the STIL gene. Pregnancy between blood relatives can also raise the chance, because relatives are more likely to carry the same gene change.
Inheritance of STIL variants
STIL-related conditions that are clearly established in human genetics are inherited in an autosomal recessive pattern. In practical terms, how STIL gene variants are inherited usually means a child receives one altered copy of the STIL gene from each parent. Parents who each carry one variant are often unaffected themselves, and with each pregnancy there is a 25% chance the child will inherit both altered copies, a 50% chance the child will be a carrier, and a 25% chance the child will inherit neither variant. This pattern applies to the well-known STIL-associated condition affecting brain growth and head size.
What does my STIL result mean for my family?
For families with a disease-causing change in the STIL gene, the pattern is usually recessive, which means parents are often healthy carriers. Brothers and sisters may also be carriers, and in some families an affected sibling may already be present or could be born in the future. Close relatives may want to learn whether the same gene change runs in the family.
Genetic information
Genetic testing
How you find out about variants
To look for changes linked to the STIL gene, labs use STIL gene genetic testing on a blood or saliva sample. The test reads the gene's DNA code to identify variants and can show whether a person carries a variant that helps explain a diagnosed condition or a family history.
When should I consider getting a genetic test?
Testing may be worth considering if a baby or child has a much smaller-than-expected head size from before birth or early life, especially with developmental delays, or if this runs in the family. STIL testing can help confirm whether an inherited change is the cause.
A genetic result is only one part of your health story
A genetic result can provide useful insight, but how much it reveals depends on the condition and on the type of variant. Over time, many factors, including lifestyle, environment, age, and medical history, also influence how the body functions. In some conditions, especially those affected by many genes, genetic information offers context rather than certainty and is best interpreted alongside other parts of care. In other situations, a genetic result may give 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 responds to medicines. Small differences in genes can change how a drug is broken down, how strongly it works, or how sensitive you are to side effects. This helps explain why the same treatment may work well for one person but less well for another, even when they take the same medication.
What is Pharmacogenetics?
Pharmacogenetics examines how genetic differences can affect the way a person responds to medication. It focuses on the relationship between genes and drugs to help explain why the same treatment may work differently from one person to another. For many medicines, genes influence both how strongly a drug works and how the body handles it. This understanding can support treatment decisions that are better informed and more individualized. You can read more about this topic in the LearnHub.
Drugs influenced by the STIL gene
When should I seek medical advice?
There is not yet a broadly confirmed role for this gene in guiding medication choice or response, so questions about side effects, new symptoms, or how a medicine is working are best discussed with your doctor.
History
The STIL gene first drew attention in the early 1990s during studies of T cell leukemia, when researchers found that changes in this stretch of DNA could disrupt nearby gene activity. It was originally named for its location as the “SCL/TAL1 interrupting locus,” reflecting that discovery path. From these first observations, research expanded steadily. In the years that followed, scientists connected the STIL gene to inherited conditions affecting brain growth, which broadened interest beyond cancer research. Later work placed it among a group of genes important in early human development and cell division. The way this gene was viewed has shifted over time, moving from a leukemia linked finding to a clearer place in developmental genetics.