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MSH3
mutS homolog 3
The MSH3 gene provides instructions for making a protein critical to DNA mismatch repair, a process that corrects errors during DNA replication to maintain genomic stability. The MSH3 gene is integral to the cellular machinery responsible for fixing inaccuracies that can arise when DNA is copied, helping to prevent the accumulation of mutations.
MSH3 is located on the long (q) arm of chromosome 5, at band 5q14.1. Arm ratio per GRCh38 - banding schematic.
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Overview
The MSH3 gene, also known as mutS homolog 3, plays a vital role in maintaining the integrity of our genetic material. It encodes a protein that is a key component of the DNA mismatch repair (MMR) system, a sophisticated cellular mechanism designed to detect and correct errors that occur during DNA replication. Such errors can lead to mutations that contribute to various health issues, including cancer development.
Inherited changes within the MSH3 gene can impair how effectively this DNA repair pathway functions. When the mismatch repair system is compromised, cells are more susceptible to accumulating genetic alterations. This elevated mutation rate is associated with a predisposition to certain types of cancer, positioning MSH3 as an important gene in the context of hereditary cancer risk.
What the gene does
The MSH3 gene produces the MSH3 protein, which forms part of a larger protein complex called MutSβ. This MutSβ complex, comprising MSH2 and MSH3 proteins, is specifically responsible for recognising and binding to particular types of DNA errors. These common errors frequently originate during DNA replication when the DNA polymerase enzyme slips, resulting in an extra or missing DNA building block on one of the strands.
Upon detection of these specific DNA mismatches by MutSβ, other proteins involved in the mismatch repair pathway are recruited. This recruitment initiates a sequence of events that ultimately leads to the removal of the incorrect DNA segment. The segment is then replaced with the correct sequence, thereby restoring the original genetic information. The MSH3 protein's capacity to accurately identify these DNA errors is crucial for the overall efficiency and faithfulness of the mismatch repair system. If MSH3 function is compromised, the cell's ability to correct these replication errors is diminished, leading to an increased rate of spontaneous mutations throughout the genome.
Such an accumulation of mutations can affect genes that control cell growth and division, potentially leading to uncontrolled cell proliferation and an elevated risk of cancer development.
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Chromosome location
The MSH3 gene is located on the long arm of chromosome 5, specifically at position 5q14.1. Chromosomes are highly organised structures found within the nucleus of eukaryotic cells, carrying genetic information in the form of DNA. The designation '5q14.1' indicates that the MSH3 gene is found on chromosome 5, within region 14.1 of its q (long) arm. This precise genomic address helps scientists and clinicians pinpoint the gene's position and study its contribution to human health.
Protein structure
The MSH3 protein is composed of 1137 amino acid residues. Its structural organisation is essential for its function within the DNA mismatch repair pathway. Key regions within the MSH3 protein include two distinct disordered regions; one spans amino acids 31-122, and another is found between amino acids 201-222. Disordered regions are dynamic and often involved in protein-protein interactions and regulatory functions. Furthermore, a specific region from amino acids 75-297 facilitates interaction with EXO1, another protein involved in the DNA repair pathway.
Key variants
Genetic variants in the MSH3 gene can range from single nucleotide changes to larger deletions or duplications. The impact of these variants on protein function can vary significantly. Some variants may be benign, having no effect on the MSH3 protein's ability to participate in DNA repair. However, other variants, particularly those classified as pathogenic or likely pathogenic, can disrupt the protein's structure or function, leading to a compromised DNA mismatch repair system. These functional alterations can result in an increased accumulation of mutations throughout the genome, thereby predisposing individuals to certain health conditions, particularly cancer. Given that the MSH3 protein includes disordered regions important for interactions and a binding site for the EXO1 protein, variants affecting these regions may particularly impair the protein's ability to coordinate effective DNA repair responses.
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.2814delG | - | Pathogenic | ★★☆☆ | Hereditary cancer-predisposing syndrome |
c.1017_1018insC | p.Ile340fs | Pathogenic/Likely pathogenic | ★★☆☆ | not provided |
c.1022del | p.Gly341fs | Pathogenic/Likely pathogenic | ★★☆☆ | not provided |
c.1035del | p.Pro346_Leu347insTer | Pathogenic | ★★☆☆ | not provided |
c.1040del | p.Leu347fs | Pathogenic/Likely pathogenic | ★★☆☆ | not provided |
c.1060dup | p.Val354fs | Pathogenic/Likely pathogenic | ★★☆☆ | not provided |
c.1087dup | p.Thr363fs | Pathogenic/Likely pathogenic | ★★☆☆ | Hereditary cancer-predisposing syndrome |
c.1116del | p.Glu373fs | Pathogenic/Likely pathogenic | ★★☆☆ | not provided |
c.1144A>T | p.Lys382Ter | Pathogenic/Likely pathogenic | ★★☆☆ | not provided |
c.1148_1149del | p.Lys383fs | Pathogenic | ★★☆☆ | Hereditary cancer-predisposing 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
Pathogenic variants in the MSH3 gene are primarily associated with an increased predisposition to certain types of cancer. While MSH3 is known for its role in DNA mismatch repair, inherited variations can impair this crucial cellular process, leading to a higher risk of developing tumours. Individuals carrying such variants may have a genetically inherited susceptibility that warrants careful medical management and screening.
No disease links recorded for this gene in our reference set.
Inheritance pattern
Conditions caused by pathogenic MSH3 variants typically follow autosomal recessive inheritance.
When both parents are carriers, each child has a 25% chance of being affected, 50% of being a carrier, and 25% of being unaffected.
UK clinical status
Diet & lifestyle considerations
Maintaining a healthy lifestyle is a general recommendation for overall well-being and may play a supporting role in mitigating cancer risk, although specific evidence directly linking lifestyle interventions to MSH3-related conditions is limited. Research suggests that a balanced diet rich in fruits, vegetables, and whole grains, combined with regular physical activity, can contribute to general cellular health. Avoiding smoking and excessive alcohol consumption are also widely recognised as important measures to reduce general cancer risk. These general health recommendations are not specific to MSH3 variants but represent established public health advice for cancer prevention in the general population. Individuals with a genetic predisposition should discuss personalised risk management strategies with their healthcare provider.
Supplement considerations
There is no conclusive scientific evidence to support the use of specific dietary supplements to prevent or treat conditions associated with MSH3 gene variants. No supplement has been shown to restore proper MSH3 protein function or correct DNA mismatch repair deficiencies. While some supplements may be advertised for general health benefits or cancer prevention, these claims are not specific to inherited genetic predispositions like those involving MSH3. Individuals considering any dietary supplements should consult with their general practitioner or a registered dietitian, especially if they have a known genetic predisposition or are undergoing medical treatment.
Frequently asked questions
What is the primary function of the MSH3 gene?
The MSH3 gene provides instructions for making a protein that is a key component of the DNA mismatch repair system. This system corrects errors that occur during DNA replication, helping to maintain the stability of the genome.
How does MSH3 relate to cancer risk?
Variants in the MSH3 gene can impair the DNA mismatch repair system. This can lead to an accumulation of mutations in cells, which increases an individual's predisposition to developing certain types of cancer.
What kind of protein does MSH3 produce?
MSH3 produces a protein that, along with MSH2 protein, forms the MutSβ complex. This complex identifies and binds to specific types of DNA replication errors, particularly insertion-deletion loops, and initiates their repair.
Where is the MSH3 gene located in the human genome?
The MSH3 gene is located on the long arm of chromosome 5, at position 5q14.1. This precise location helps in genetic mapping and studying its role in human health.
Are there any specific lifestyle recommendations for individuals with MSH3 variants?
While there are no specific lifestyle recommendations solely for MSH3 variants, general healthy living practices like a balanced diet, regular exercise, and avoiding smoking and excessive alcohol are advised for overall health and may reduce general cancer risk. Consult a healthcare provider for personalised advice.