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CBL
Cbl proto-oncogene
The CBL gene provides instructions for making a protein that plays a critical role in cellular signalling pathways, particularly in regulating cell growth, differentiation, and immune responses. Mutations in the CBL gene are associated with an increased risk of developing various conditions, including certain types of cancer.
CBL is located on the long (q) arm of chromosome 11, at band 11q23.3. Arm ratio per GRCh38 - banding schematic.
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Overview
The CBL proto-oncogene (CBL) is a crucial component of multiple cellular signalling networks, acting as a negative regulator of receptor tyrosine kinases (RTKs). RTKs are a class of cell surface receptors that control essential cellular processes such as growth, proliferation, differentiation, and survival.
The CBL protein achieves its regulatory function primarily through its E3 ubiquitin ligase activity, which tags specific proteins for degradation. Dysregulation of CBL's activity can lead to uncontrolled cell proliferation and is implicated in the development of several human diseases, including various cancers and developmental disorders.
What the gene does
The CBL gene encodes a protein that functions as an E3 ubiquitin ligase, an enzyme that attaches ubiquitin tags to specific target proteins. This ubiquitination often marks proteins for degradation through the proteasome system, thereby controlling their abundance and activity within the cell. In the context of RTK signalling, CBL typically acts to downregulate activated RTKs, preventing excessive or prolonged signalling.
Upon activation of RTKs by growth factors or other extracellular signals, CBL is recruited to the activated receptor complexes. Here, its E3 ubiquitin ligase activity is directed towards the RTK itself or associated signalling proteins, leading to their ubiquitination and subsequent degradation or trafficking from the cell surface. This regulatory mechanism is vital for maintaining cellular homeostasis and preventing abnormal cell growth. CBL also interacts with various other signalling molecules, modulating pathways involved in immune cell activation, cytoskeletal organisation, and cell adhesion. Pathogenic variants in CBL can disrupt this critical regulatory function, contributing to disease phenotypes characterised by aberrant cell signalling.
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Chromosome location
The CBL gene is located on chromosome 11, specifically at band 11q23.3. This region of the human genome contains numerous genes vital for normal physiological function. The precise location on this chromosome helps geneticists and clinicians to identify and study its role in health and disease.
Protein structure
The CBL protein is 906 amino acids in length and exhibits a complex domain architecture essential for its diverse functions. The N-terminal region, spanning amino acids 1-357, is sufficient for interaction with EPHB1. Within this region, the first 21 amino acids constitute a Disordered region. A key functional area is the Cbl-PTB (Domain), located from amino acids 47-351, which is crucial for its phosphotyrosine binding capabilities. This Cbl-PTB domain contains a 4H (Region) from amino acids 47-175, an EF-hand-like (Region) from amino acids 176-248, and an SH2-like (Region) from amino acids 249-351.
Following the Cbl-PTB domain, a Linker (Region) is found from amino acids 352-380. The region from amino acids 358-906 is required for the ubiquitination of SPRED2. A critical component of its E3 ubiquitin ligase activity is the RING-type (Zinc finger) domain, located between amino acids 381-420. The protein also contains several Disordered regions: one from amino acids 432-462, another from 477-498, a longer one from 519-667, and additional disordered segments from 680-719 and 743-781. The segment from amino acids 648-906 is involved in interaction with CD2AP.
Key variants
Variants in the CBL gene can range from single nucleotide changes to larger deletions or duplications. Pathogenic variants lead to an altered CBL protein that functions improperly or is not produced at all. These changes can disrupt the protein's ability to regulate cell signalling pathways, leading to uncontrolled cell growth or altered cellular responses. Identification of specific CBL variants helps in understanding the genetic basis of associated conditions and informs potential clinical management strategies.
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.1096-1G>C | - | Pathogenic/Likely pathogenic | ★★☆☆ | CBL-related disorder |
c.1096-1G>T | - | Pathogenic | ★★☆☆ | CBL-related disorder |
c.1096-2A>T | - | Pathogenic | ★★☆☆ | CBL-related disorder |
c.1096-4_1096-1del | - | Pathogenic/Likely pathogenic | ★★☆☆ | CBL-related disorder |
c.1099_1101del | p.Gln367del | Pathogenic/Likely pathogenic | ★★☆☆ | CBL-related disorder |
c.1100A>C | p.Gln367Pro | Pathogenic/Likely pathogenic | ★★☆☆ | not provided |
c.1111T>A | p.Tyr371Asn | Pathogenic/Likely pathogenic | ★★☆☆ | Neurodevelopmental disorder |
c.1111T>C | p.Tyr371His | Pathogenic/Likely pathogenic | ★★☆☆ | Noonan syndrome-like disorder with juvenile myelomonocytic leukemia |
c.1111T>G | p.Tyr371Asp | Pathogenic/Likely pathogenic | ★★☆☆ | CBL-related disorder |
c.1112A>C | p.Tyr371Ser | Pathogenic/Likely pathogenic | ★★☆☆ | RASopathy |
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 CBL gene are associated with a variety of conditions, primarily related to aberrations in cellular signalling and proliferation. As a proto-oncogene, alterations can lead to an increased risk of cancer. The inheritance pattern of conditions linked to CBL is autosomal dominant (AD), meaning that only one copy of an altered gene is sufficient to increase disease risk.
No disease links recorded for this gene in our reference set.
Inheritance pattern
Conditions caused by pathogenic CBL variants typically follow autosomal dominant inheritance.
Each child has a 50% chance of inheriting the pathogenic variant, regardless of sex.
UK clinical status
The CBL gene is recognised within the UK's National Health Service (NHS) Genomic Medicine Service. It is included in several Green panel nominations on PanelApp, indicating strong evidence for its association with specific conditions. These include panels for Adult solid tumours cancer susceptibility, Cerebral vascular malformations (R336), Childhood solid tumours, Childhood solid tumours cancer susceptibility, DDG2P, Embryonal tumour of possible germline origin (R456), Foetal anomalies (R21), Foetal hydrops, Haematological malignancies cancer susceptibility, Haematological malignancies for rare disease, Intellectual disability (R29), IUGR and IGF abnormalities, Monogenic short stature (R453), Pigmentary skin disorders (R236), Primary lymphoedema (R136), RASopathies, and Sarcoma of possible germline origin (R457).
Sources: NHS GMS PanelApp · Genomics England PanelApp · NHS National Genomic Test Directory
Diet & lifestyle considerations
Maintaining a healthy lifestyle, including a balanced diet and regular physical activity, is generally recommended for overall well-being. For individuals with a genetic predisposition due to CBL variants, these general healthy living principles apply. Research suggests that lifestyle choices can influence various biological pathways, potentially modulating disease risk. However, there is no specific lifestyle intervention conclusively proven to prevent the development of conditions associated with CBL variants. General population guidelines for cancer prevention, such as avoiding tobacco and excessive alcohol, maintaining a healthy weight, and protecting skin from excessive sun exposure, are prudent.
Supplement considerations
There is no conclusive evidence to suggest that specific dietary supplements can prevent or treat conditions associated with CBL gene variants. While some supplements are marketed for their general health benefits, individuals should approach such claims with caution. It is always advisable to discuss any planned supplement intake with a healthcare professional, especially when there is a known genetic predisposition or existing health condition, to ensure safety and avoid potential interactions.
Frequently asked questions
What is the primary function of the CBL gene?
The CBL gene encodes a protein that acts as an E3 ubiquitin ligase, primarily regulating receptor tyrosine kinases (RTKs) by tagging them for degradation. This process helps control cell growth, proliferation, and immune responses.
How can variants in the CBL gene affect health?
Pathogenic variants in the CBL gene can disrupt the protein's ability to properly regulate cell signalling. This can lead to uncontrolled cell growth and is associated with an increased risk for various conditions, including different types of cancer and developmental disorders.
Is a CBL variant considered an autosomal dominant inheritance?
Yes, conditions associated with pathogenic CBL variants typically follow an autosomal dominant inheritance pattern. This means only one copy of the altered gene is sufficient to increase the risk of developing the associated condition.
Where is the CBL gene located?
The CBL gene is situated on chromosome 11, specifically at the band 11q23.3. This precise genomic location is important for genetic mapping and diagnostic purposes.
Are there specific lifestyle changes to manage CBL-related risks?
While general healthy lifestyle practices like a balanced diet and regular exercise are beneficial for overall health, there is no specific lifestyle intervention conclusively proven to prevent conditions associated with CBL variants. It is always best to consult with a healthcare professional regarding personalized advice.