On this page
TSC1
TSC complex subunit 1
The TSC1 gene provides instructions for producing hamartin, a protein that plays a vital role in regulating cell growth, proliferation, and size. Hamartin, produced from the TSC1 gene, interacts with tuberin (from the TSC2 gene) to form a complex that acts as a tumour suppressor.
TSC1 is located on the long (q) arm of chromosome 9, at band 9q34.13. Arm ratio per GRCh38 - banding schematic.
Explore chromosome 9 in the library →Available at Jeen Health
Clinical tests that include this
Overview
The TSC1 gene encodes a protein called hamartin, which is a key component of the tuberous sclerosis complex (TSC) pathway. This pathway is essential for controlling how cells grow, divide, and specialise, functioning as a tumour suppressor mechanism throughout the body. Pathogenic variants in TSC1 are linked to several inherited conditions, most notably Tuberous Sclerosis Complex, a disorder affecting multiple body systems characterised by the development of benign tumours in various organs.
The hamartin protein works together with tuberin (encoded by the TSC2 gene) to form a complex that regulates a significant cellular signalling pathway. This TSC1-TSC2 complex is crucial for maintaining cellular health and preventing abnormal tissue growth, influencing a range of clinical presentations.
Understanding the role of the TSC1 gene is important for the diagnosis and management of conditions stemming from its dysfunction. Its function as a tumour suppressor highlights its importance in cellular health and preventing unchecked tissue development, impacting a variety of clinical manifestations.
What the gene does
The TSC1 gene carries the genetic blueprint for producing hamartin, a protein critical for governing cellular expansion and division. Inside cells, hamartin collaborates with tuberin, a protein derived from the TSC2 gene. Together, these two proteins assemble into a complex that helps to regulate both the size of cells and their ability to grow and multiply.
Proteins that normally impede cells from undergoing excessive or unregulated growth and division are referred to as tumour suppressors. Hamartin and tuberin fulfil this tumour suppressor function by interacting with and modulating a wide array of other proteins involved in cellular processes. This role is vital for maintaining cellular balance and preventing the uncontrolled multiplication of cells.
Video: Genetics 101
Chromosome location
The TSC1 gene is found on chromosome 9, specifically at the 9q34.13 position. This chromosomal address pinpoints its precise location within the human genome. The gene occupies a substantial DNA segment, and its exact structure includes numerous exons and introns. Identifying this specific location is important for mapping and understanding the genetic basis of conditions associated with TSC1.
Protein structure
The hamartin protein, which the TSC1 gene instructs the cell to build, consists of 1164 amino acids. Its structural arrangement features several distinct regions that are vital for its function and interactions. A key segment spanning amino acids 403-787 is involved in mediating interactions with WDR45B, suggesting its role in protein complex formation and cellular trafficking. The protein also contains multiple regions that lack a fixed three-dimensional structure; one is located between amino acids 439-571, another between 1006-1085, and a third at the C-terminus from amino acids 1131-1164. These disordered regions often allow for flexibility and facilitate interactions with various binding partners. Furthermore, a coiled-coil domain is present from amino acids 721-997. Coiled-coil structures are common protein motifs that enable protein-protein interactions and are often involved in oligomerisation, which is crucial for the formation of the hamartin-tuberin complex.
Key variants
Pathogenic variants within the TSC1 gene are diverse, encompassing a range of genetic alterations. These can include small deletions, insertions, or substitutions of DNA building blocks (nucleotides), as well as larger genomic rearrangements. Many variants lead to a premature stop signal in the gene's instructions, resulting in a truncated, non-functional hamartin protein. Other variants may alter critical amino acids, disrupting the protein's structure or its ability to interact with tuberin or other cellular components. The specific type and location of a variant can influence the severity and presentation of associated conditions.
Sample of pathogenic variants
10 pathogenic / likely-pathogenic variants from ClinVar, ranked by review status (expert-panel-reviewed first). This is a sample; recurrent founder variants in a specific population may not appear here - see the full ClinVar listing via the link above.
| Variant (HGVS) | Protein change | Classification | Evidence | Associated condition |
|---|---|---|---|---|
c.1005dup | p.Arg336fs | Pathogenic/Likely pathogenic | ★★☆☆ | Tuberous sclerosis 1 |
c.1015dup | p.Thr339fs | Pathogenic | ★★☆☆ | Tuberous sclerosis 1 |
c.1027C>T | p.Gln343Ter | Pathogenic | ★★☆☆ | Tuberous sclerosis 1 |
c.1029+1G>A | - | Pathogenic/Likely pathogenic | ★★☆☆ | Tuberous sclerosis syndrome |
c.1029+1G>C | - | Pathogenic/Likely pathogenic | ★★☆☆ | Tuberous sclerosis 1 |
c.1041G>A | p.Trp347Ter | Pathogenic | ★★☆☆ | Malignant tumor of urinary bladder |
c.107-1G>A | - | Pathogenic/Likely pathogenic | ★★☆☆ | not provided |
c.1101_1114del | p.Asp368fs | Pathogenic | ★★☆☆ | Tuberous sclerosis syndrome |
c.1119C>G | p.Tyr373Ter | Pathogenic | ★★☆☆ | Tuberous sclerosis 1 |
c.1125dup | p.Val376fs | Pathogenic/Likely pathogenic | ★★☆☆ | not provided |
Evidence stars indicate ClinVar review status. Individual variant interpretation should always be performed by a qualified clinical laboratory - many variants remain classified as Variants of Uncertain Significance (VUS) pending more research.
Associated conditions
Pathogenic variants in the TSC1 gene are primarily linked to Tuberous Sclerosis Complex, an autosomal dominant disorder characterised by the growth of benign tumours in various organs, including the brain, kidneys, heart, lungs, and skin. TSC1 variants can also cause Lymphangioleiomyomatosis (LAM), a destructive lung disease involving abnormal smooth muscle-like tissue overgrowth. Additionally, inherited TSC1 variants have been associated with Focal cortical dysplasia (type II), a brain malformation that can lead to severe epilepsy.
Inheritance pattern
Conditions caused by pathogenic TSC1 variants typically follow autosomal dominant inheritance.
Each child has a 50% chance of inheriting the pathogenic variant, regardless of sex.
UK clinical status
In the UK, the TSC1 gene is extensively evaluated within the NHS Genomic Medicine Service due to its strong association with a range of inherited conditions. It is classified as a 'green' gene across numerous NHS England National Genomic Test Directory panels, indicating that there is strong evidence for its pathogenicity in these contexts. This includes panels such as 'Classical tuberous sclerosis', 'Tuberous sclerosis (R228)', 'Early onset or syndromic epilepsy', and 'Intellectual disability'. Furthermore, TSC1 is assessed in cancer susceptibility panels for 'Adult solid tumours cancer susceptibility' and 'Childhood solid tumours cancer susceptibility', highlighting its role in tumour formation. Its inclusion in 'Foetal anomalies (R21)', 'Pigmentary skin disorders (R236)', 'Pneumothorax - familial (R190)', 'Primary lymphoedema (R136)', and 'Unexplained kidney failure in young people' panels further demonstrates its broad clinical relevance in the UK.
Sources: NHS GMS PanelApp · Genomics England PanelApp · NHS National Genomic Test Directory
Diet & lifestyle considerations
Research suggests that general lifestyle factors can play a role in overall health, though there is no conclusive evidence that specific lifestyle changes can prevent the development or progression of conditions associated with TSC1 gene variants. Maintaining a balanced diet rich in fruits, vegetables, and whole grains is generally recommended for overall well-being. Regular physical activity, within one's capabilities, can support cardiovascular health and mood. Avoiding smoking and excessive alcohol consumption is beneficial for general health and can help reduce the risk of various conditions. Individuals with conditions related to TSC1 should discuss any lifestyle modifications with their healthcare provider to ensure they are appropriate for their specific health needs.
Supplement considerations
Currently, there is no conclusive scientific evidence to suggest that specific dietary supplements can prevent, treat, or cure conditions associated with TSC1 gene variants. Any claims regarding supplements for these conditions should be viewed with caution. While some supplements may be promoted for general health benefits, individuals with a TSC1 variant or an associated condition should consult with a healthcare professional before taking any new supplements. A healthcare provider can offer personalised advice, assess potential interactions with existing medications, and ensure that any chosen supplements are safe and appropriate for their individual health circumstances.
Frequently asked questions
What does the TSC1 gene do?
The TSC1 gene provides instructions for making the hamartin protein. This protein works with tuberin (from the TSC2 gene) to form a complex that helps regulate cell growth, division, and size, acting as a tumour suppressor.
What conditions are associated with TSC1 gene variants?
Variants in the TSC1 gene are primarily associated with Tuberous Sclerosis Complex, a condition involving benign tumour growth in multiple organs. They can also cause Lymphangioleiomyomatosis (LAM) and Focal cortical dysplasia (type II).
Is Tuberous Sclerosis Complex always inherited?
Tuberous Sclerosis Complex can be inherited in an autosomal dominant pattern. However, a significant number of cases arise from new (de novo) genetic variants that are not inherited from a parent.
Can lifestyle changes prevent conditions associated with TSC1 variants?
While a healthy lifestyle is beneficial for general well-being, there is no conclusive evidence that specific lifestyle changes can prevent the development or progression of conditions associated with TSC1 gene variants. Always consult a healthcare provider for personalised advice.
Are there any supplements that can help with TSC1-related conditions?
Currently, there is no conclusive scientific evidence that specific dietary supplements can prevent, treat, or cure conditions associated with TSC1 gene variants. It is important to discuss any supplement use with a healthcare professional.
References
- Martignoni G, Pea M, Reghellin D. Molecular pathology of lymphangioleiomyomatosis and other perivascular epithelioid cell tumors. Archives of pathology & laboratory medicine. 2010. PMID: 20073603
- Adam MP, Bick S, Mirzaa GM. Tuberous Sclerosis Complex. 1993. PMID: 20301399