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AXIN2
axin 2
The AXIN2 gene provides instructions for a protein that is a crucial component of the Wnt signalling pathway, which regulates cell growth, development, and differentiation. The AXIN2 gene encodes the axin 2 protein, an essential factor in cellular processes such as cell proliferation and body axis formation.
AXIN2 is located on the long (q) arm of chromosome 17, at band 17q24.1. Arm ratio per GRCh38 - banding schematic.
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Overview
The AXIN2 gene, also known as axin 2, plays a vital role in human development and cellular function. It is a key component of the Wnt signalling pathway, a complex network of proteins that orchestrates numerous biological processes, including embryonic development, cell differentiation, and tissue homeostasis. The protein produced from the AXIN2 gene acts as a scaffold, bringing together other proteins involved in this pathway to regulate its activity.
Disruptions to the normal function of AXIN2, often due to genetic variants, can lead to uncontrolled cell growth and differentiation. This can contribute to an increased risk of developing inherited conditions, particularly certain types of cancer. Understanding the AXIN2 gene and its role is important for genetic counselling and risk assessment.
What the gene does
The AXIN2 gene encodes a protein that acts as a central component within the Wnt signalling pathway, functioning primarily as a tumour suppressor. In the absence of Wnt signalling, the AXIN2 protein helps to form what is known as the "destruction complex". This complex includes proteins like adenomatous polyposis coli (APC), glycogen synthase kinase 3 beta (GSK3B), and casein kinase 1 (CK1).
The primary role of this destruction complex is to facilitate the degradation of beta-catenin, a key transcription factor in the Wnt pathway. By phosphorylating beta-catenin, the complex targets it for ubiquitination and subsequent proteasomal degradation, thus keeping Wnt signalling suppressed. When Wnt ligands are present, they bind to their receptors, initiating a cascade that inactivates the destruction complex. This allows beta-catenin to accumulate in the cytoplasm and then translocate to the nucleus, where it activates target genes involved in cell proliferation, differentiation, and survival.
Therefore, AXIN2's role as a negative regulator is critical for preventing excessive Wnt pathway activation, which, if left unchecked, can lead to uncontrolled cell division and tumour formation. This regulatory function underscores its importance in maintaining cellular homeostasis.
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Chromosome location
The AXIN2 gene is situated on the long (q) arm of chromosome 17, specifically at position 24.1. This genomic location is commonly referred to as 17q24.1. The gene spans approximately 48 kilobases and is composed of 10 exons. It directs the synthesis of the axin 2 protein, which is 843 amino acids in length. The precise location on chromosome 17 means that any genetic alterations within this region could potentially impact AXIN2 function and, consequently, its role in Wnt signalling.
Protein structure
The axin 2 protein, encoded by the AXIN2 gene, is 843 amino acids long and features several distinct domains and regions critical for its function in the Wnt signalling pathway. These include a Disordered region at the N-terminus (amino acids 1-75) and another Disordered region (amino acids 396-435).
A Tankyrase-binding motif is located between amino acids 21-30. The RGS (Regulator of G-protein Signalling) Domain, involved in protein-protein interactions, spans amino acids 81-200. Further along the protein, there is a region for Interaction with GSK3B (amino acids 327-413), highlighting its role in the destruction complex. Overlapping with this region is the Interaction with SIAH1 and SIAH2 region (amino acids 334-393). The Interaction with beta-catenin region is found between amino acids 413-476, vital for regulating beta-catenin levels. Additional Disordered regions are present at amino acids 447-494, 561-674, and 718-748. Finally, the C-terminal end contains the DIX (Dishevelled and Axin) Domain, from amino acids 761-843, which is important for polymerisation and interaction with other Wnt pathway components.
Key variants
Genetic variants in the AXIN2 gene can alter the structure or function of the axin 2 protein, potentially disrupting its crucial role in regulating the Wnt signalling pathway. These variants may include single nucleotide changes, insertions, or deletions within the gene sequence. Depending on their nature and location, such variants can lead to a protein that is less effective, non-functional, or even excessively active. Pathogenic variants can impair the protein's ability to assemble the beta-catenin destruction complex, leading to its accumulation and uncontrolled activation of Wnt target genes. Such disruptions can result in various health implications, especially an increased susceptibility to certain inherited conditions, including cancer predisposition syndromes. The impact of a specific AXIN2 variant often depends on its exact effect on protein function.
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.1032del | p.Asn344fs | Pathogenic | ★★☆☆ | Oligodontia-cancer predisposition syndrome |
c.1150G>T | p.Glu384Ter | Pathogenic/Likely pathogenic | ★★☆☆ | Colorectal cancer |
c.1186C>T | p.Gln396Ter | Pathogenic/Likely pathogenic | ★★☆☆ | Oligodontia-cancer predisposition syndrome |
c.1212_1215del | p.Glu405fs | Pathogenic | ★★☆☆ | Oligodontia-cancer predisposition syndrome |
c.1214_1215del | p.Glu405fs | Pathogenic | ★★☆☆ | Oligodontia-cancer predisposition syndrome |
c.1249del | p.Ala417fs | Pathogenic | ★★☆☆ | Oligodontia-cancer predisposition syndrome |
c.1274dup | p.Leu426fs | Pathogenic | ★★☆☆ | Hereditary cancer-predisposing syndrome |
c.1306C>T | p.Gln436Ter | Pathogenic | ★★☆☆ | Hereditary cancer-predisposing syndrome |
c.130C>T | p.Gln44Ter | Pathogenic | ★★☆☆ | Oligodontia-cancer predisposition syndrome |
c.1329dup | p.Ser444fs | Pathogenic | ★★☆☆ | Oligodontia-cancer predisposition syndrome |
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
Variants in the AXIN2 gene are primarily associated with hereditary cancer predisposition. The gene's role as a negative regulator of the Wnt signalling pathway means that impaired function can lead to increased cell proliferation and an elevated risk of tumour formation. While specific conditions are related to AXIN2, they often manifest as an increased susceptibility to certain cancers. This highlights the importance of AXIN2 in maintaining cellular homeostasis and preventing uncontrolled cell growth.
No disease links recorded for this gene in our reference set.
Inheritance pattern
Conditions caused by pathogenic AXIN2 variants typically follow autosomal dominant inheritance.
Each child has a 50% chance of inheriting the pathogenic variant, regardless of sex.
UK clinical status
The AXIN2 gene is recognised within the UK's Genomics England PanelApp, indicating its clinical relevance in inherited conditions. It is listed on the Ectodermal dysplasia panel (R163) with a 'green' status. A 'green' status signifies that there is sufficient evidence for a strong association between variants in AXIN2 and the development of ectodermal dysplasia, and it is routinely considered in diagnostic testing for this condition within the NHS Genomic Medicine Service.
Sources: NHS GMS PanelApp · Genomics England PanelApp · NHS National Genomic Test Directory
Diet & lifestyle considerations
Maintaining a healthy lifestyle is generally recommended for individuals, particularly those with a genetic predisposition to certain conditions. For conditions potentially associated with AXIN2 variants, general recommendations typically include a balanced diet rich in fruits, vegetables, and whole grains, and low in processed foods and red meat. Regular physical activity, maintaining a healthy weight, and avoiding smoking and excessive alcohol consumption are also widely encouraged. These lifestyle choices can contribute to overall well-being and may help mitigate general health risks.
Supplement considerations
Currently, there is no conclusive scientific evidence to suggest that specific dietary supplements can prevent or treat conditions associated with AXIN2 variants. Individuals should exercise caution regarding any claims about supplements curing or preventing genetic conditions. It is important to discuss any interest in taking supplements with a healthcare provider to ensure they are safe and appropriate for individual health needs, especially given potential interactions with medications or existing health conditions.
Frequently asked questions
What is the AXIN2 gene?
The AXIN2 gene provides instructions for making the axin 2 protein, which is a key component of the Wnt signalling pathway. This pathway is crucial for cell growth, development, and differentiation.
What is the function of the AXIN2 protein?
The AXIN2 protein acts as a negative regulator in the Wnt signalling pathway. It helps to form a 'destruction complex' that breaks down beta-catenin, a protein that promotes cell growth, thereby helping to control cell proliferation.
What kinds of problems are associated with AXIN2 variants?
Variants in the AXIN2 gene are primarily associated with an increased genetic predisposition to certain types of cancer and other developmental conditions due to the disruption of normal cell growth regulation.
How is AXIN2 relevant in the UK healthcare system?
The AXIN2 gene is part of the UK's Genomics England PanelApp for Ectodermal dysplasia, indicating its established clinical importance for diagnostic testing within the NHS Genomic Medicine Service.
Can lifestyle changes help with AXIN2-related conditions?
While no specific lifestyle changes can cure or prevent AXIN2-related conditions, generally healthy habits such as a balanced diet and regular exercise are recommended for overall well-being and may help manage general health risks.