The SHANK3 gene helps nerve cells in the brain connect and pass signals to each other. If it does not work properly, a person may have delayed speech and learning, low muscle tone, and differences in behavior or social communication; some also have autism, sleep problems, or seizures. This gene plays an important role in brain development, and more disruptive variants are a known cause of Phelan-McDermid syndrome.
What is a gene?
Genes are sections of DNA that carry instructions your cells use to make molecules or manage processes in the body. Some genes provide the information needed to produce proteins, the cell parts that do much of the work. Others mainly help regulate when certain processes happen, where they take place, and how active they are. Together, genes affect how the body develops and functions, and they can influence how you respond to food, stress, or medications. To go into this topic in more detail, you can find more in the LearnHub.
Overview
SHANK3Gene function
What if the gene works
The SHANK3 gene helps build and organize connections between nerve cells, especially in the brain. Its protein supports signaling at synapses, which helps with learning, communication, and everyday brain function.
Risk
What if the gene does not work
More disruptive variants in the SHANK3 gene often cause developmental delay, limited speech, low muscle tone, autism traits, and intellectual disability. Milder variants can cause a broader, often less marked range of features.
Treatment
What does that mean for your treatment
For a pathogenic or loss-of-function variant in the SHANK3 gene, no gene-specific treatment or medication strategy is currently established in clinical guidelines. Medicines are chosen for the person’s symptoms, such as seizures, sleep problems, attention difficulties, or mood and behavior changes, rather than for the variant itself. SHANK3-targeted approaches, including treatments aimed at brain signaling, are under study but are not standard care.
Conditions associated with SHANK3
Gene function
What if the gene works
SHANK3 helps nerve cells keep their contact points orderly and responsive. In your brain, this gene supports processes that let these cells send and receive messages in a coordinated way. Understanding how the SHANK3 gene works in the brain helps show how synapses stay stable during everyday signaling.
The SHANK3 gene helps build the inner framework of excitatory synapses, the contact points where many brain cells pass signals. Its protein acts like a platform that holds key signaling parts in the right place.
Inside these synapses, the SHANK3 gene helps connect surface receptors with nearby helper proteins. This lets messages move from one nerve cell to the next in an organized sequence.
This gene also links synapse proteins to actin, a structural material that helps shape dendritic spines (small receiving bumps on nerve cells). That support helps these receiving sites stay steady during normal brain activity.
Its protein also supports the growth and routine upkeep of mature synapses. This helps communication sites remain ready for repeated use as brain circuits stay active.
What is a variant?
A genetic variant is a small difference in the DNA sequence of a gene. These changes are common and are part of normal human diversity, including differences in appearance, metabolism, or how the body responds to environmental influences. Many variants do not have any noticeable effect and simply represent natural genetic variation. In some cases, though, a variant can change gene function more significantly and may contribute to or cause a genetic condition.
Genetic variants
What if the gene does not work
Many SHANK3 variants change how SHANK3 variants affect brain cell communication by reducing the amount of protein made or creating a shortened, unstable protein. Others alter key regions so the protein cannot bind its partners well or stay at the synapse, the contact point between nerve cells, which weakens signaling. Milder variants may partly reduce this effect, while more severe variants, including truncating variants or larger deletions, can cause a greater loss of function and often link to earlier or broader neurodevelopmental features.
How variants are linked to conditions
Pathogenic variants in the SHANK3 gene can cause Phelan-McDermid syndrome, also called a SHANK3-related condition. This is a well-established link, and many affected people have developmental delay, very limited or absent speech, autism features, low muscle tone, and intellectual disability. Some also develop seizures or behavior and mood symptoms, although the exact pattern can vary from person to person.
A variant is not necessarily a diagnosis
Genetic variants are a usual feature of human biology and are widespread in the general population. Most do not directly affect health and instead reflect natural human variation. For many genes, having 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, 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 SHANK3, risk is mainly linked to whether a harmful gene change is present, and these changes can happen new in a child or be inherited from a parent. There is not yet broadly confirmed evidence that specific lifestyle or environmental factors meaningfully change this risk.
Inheritance of SHANK3 variants
SHANK3-related conditions are usually inherited in an autosomal dominant pattern, which means one altered copy of the SHANK3 gene can be enough to cause the condition. In families where a parent carries a disease-causing SHANK3 variant, each child has a 50% chance of inheriting it. When people ask how SHANK3 variants are inherited, an important point is that many cases happen because of a new (de novo) variant, meaning the change started in the child and was not inherited from either parent.
What does my SHANK3 result mean for my family?
For SHANK3, a disease-causing result is usually linked to a dominant pattern, so close relatives such as parents, brothers, sisters, and children may also carry the same change. In many families, though, the SHANK3 change happened new in the affected person and was not inherited from either parent. What it means for relatives depends on whether the result was inherited or new in the family.
Genetic information
Genetic testing
How you find out about variants
To find variants in the SHANK3 gene, labs analyze DNA from blood or saliva with tests such as chromosomal microarray and sequencing. Genetic testing for SHANK3 variants works by looking for missing pieces, extra pieces, or spelling changes in the gene.
When should I consider getting a genetic test?
Testing for SHANK3 may be worth considering when a child has clear developmental delay, autism, very limited speech, low muscle tone, or learning problems, especially if these happen together. It can also help if there is a family history of a related genetic condition or a known SHANK3 change.
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 specific type of variant. Many factors, including lifestyle, environment, age, and medical history, also shape how the body works over time. For some conditions, especially those influenced by many genes, genetic information adds context rather than certainty and is most informative when viewed alongside other parts of care. In other situations, a genetic result can 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 people respond to medicines. Some people break down a drug more quickly, while others process it more slowly, which can change how much benefit they get or how sensitive they are to side effects. This kind of difference is common and is one reason the same medication can work well for one person but less well for another.
What is Pharmacogenetics?
Pharmacogenetics examines the ways genetic differences can shape how people respond to medicines. By studying links between genes and drugs, it helps explain why the same treatment may work differently from one person to another. For many medicines, genes affect how strongly a drug works or how the body handles it. This information can support more informed, individualized treatment choices. More on this topic is available in the LearnHub.
Drugs influenced by the SHANK3 gene
When should I seek medical advice?
There is not yet a broadly confirmed role for this gene in guiding how medicines are chosen or used. If you have questions about side effects, how well a treatment is working, or possible medicine interactions, it is best to discuss them with your doctor or pharmacist.
History
Throughout history, people described children with low muscle tone, delayed speech, and developmental differences that were later grouped under 22q13 deletion syndrome, now often called Phelan-McDermid syndrome. In the early 2000s, researchers narrowed attention to the SHANK3 gene as a major contributor to these features. Building on this early work, scientists also linked variants in the SHANK3 gene to some cases of autism and related neurodevelopmental conditions. That discovery made the gene important in both rare disease research and broader autism genetics. Over time, descriptions became more precise as chromosome testing and DNA sequencing improved. Today, the SHANK3 gene is recognized as a key part of the history of Phelan-McDermid syndrome and modern neurodevelopmental genetics.