MSH2 — MutS Homolog 2

MSH2 — MutS Homolog 2

Introduction

Msh2 — Muts Homolog 2 is an important component in the neurobiology of neurodegenerative diseases. This page provides detailed information about its structure, function, and role in disease processes.

<!-- Gene Infobox -->
<div class="infobox infobox-gene">
<div class="infobox-header">MSH2</div>
<div class="infobox-content">
<table>
<tr><th>Full Name</th><td>MutS Homolog 2</td></tr>
<tr><th>Synonyms</th><td>MSH2, mutS homolog 2</td></tr>
<tr><th>Chromosome</th><td>2p16.3</td></tr>
<tr><th>NCBI Gene ID</th><td>4439</td></tr>
<tr><th>OMIM</th><td>604952</td></tr>
<tr><th>Ensembl ID</th><td>ENSG00000116675</td></tr>
<tr><th>UniProt ID</th><td>P43246</td></tr>
<tr><th>Protein</th><td>[MSH2 Protein](/proteins/msh2-protein)</td></tr>
<tr><th>Associated Diseases</th><td>Lynch Syndrome, Alzheimer's Disease, Parkinson's Disease, ALS</td></tr>
</table>
</div>
</div>

Overview

MSH2 — MutS Homolog 2

Introduction

Msh2 — Muts Homolog 2 is an important component in the neurobiology of neurodegenerative diseases. This page provides detailed information about its structure, function, and role in disease processes.

<!-- Gene Infobox -->
<div class="infobox infobox-gene">
<div class="infobox-header">MSH2</div>
<div class="infobox-content">
<table>
<tr><th>Full Name</th><td>MutS Homolog 2</td></tr>
<tr><th>Synonyms</th><td>MSH2, mutS homolog 2</td></tr>
<tr><th>Chromosome</th><td>2p16.3</td></tr>
<tr><th>NCBI Gene ID</th><td>4439</td></tr>
<tr><th>OMIM</th><td>604952</td></tr>
<tr><th>Ensembl ID</th><td>ENSG00000116675</td></tr>
<tr><th>UniProt ID</th><td>P43246</td></tr>
<tr><th>Protein</th><td>[MSH2 Protein](/proteins/msh2-protein)</td></tr>
<tr><th>Associated Diseases</th><td>Lynch Syndrome, Alzheimer's Disease, Parkinson's Disease, ALS</td></tr>
</table>
</div>
</div>

Overview

MSH2 (MutS Homolog 2) is a key DNA mismatch repair (MMR) gene that plays a critical role in maintaining genomic stability. The MSH2 protein forms heterodimers with MSH6 (MutSalpha) or MSH2-MSH3 (MutSbeta) to recognize base-base mismatches and small insertion/deletion loops that arise during DNA replication. Beyond its canonical role in MMR, MSH2 has been implicated in neurodegenerative diseases through mechanisms involving DNA repair deficiency, somatic mutation accumulation, and altered cellular stress responses.

Normal Function

MSH2 is essential for the DNA mismatch repair system:

MSH2 Complexes

DNA Mismatch Repair Process

Brain Expression

MSH2 is expressed in all brain cell types:

• [Neurons](/entities/neurons): High basal expression, constitutive MMR activity
• Glia: Lower expression than neurons
• Neural progenitors: Active cell cycle, requires MMR

Role in Neurodegenerative Diseases

Alzheimer's Disease

DNA damage accumulates in AD brains:

• Elevated levels of oxidative DNA lesions (8-oxoguanine)
• Somatic mutations in neurons increase with age and AD
• MSH2 expression is altered in AD brain tissue
• Impaired MMR contributes to genomic instability

Parkinson's Disease

MSH2 involvement in PD:

• Dopaminergic neurons are particularly vulnerable to DNA damage
• Mitochondrial DNA mutations accumulate in PD
• MSH2 may interact with parkin (PRKN) pathway
• DNA repair deficits contribute to neuronal death

Amyotrophic Lateral Sclerosis

• [TDP-43](/proteins/tdp-43) pathology affects DNA repair pathways
• MSH2 dysfunction may contribute to motor neuron vulnerability
• Oxidative stress overwhelms DNA repair capacity

Lynch Syndrome

While primarily a cancer predisposition syndrome:

• Some patients develop neurological symptoms
• Potential for early-onset neurodegeneration

Therapeutic Targeting

MSH2 Modulators

| Approach | Mechanism | Status |
|----------|-----------|--------|
| Gene therapy | Restore MSH2 expression | Preclinical |
| Small molecules | Enhance MMR efficiency | Discovery |
| Antioxidants | Reduce oxidative DNA damage | Clinical trials |

Animal Models

• Msh2 knockout: Embryonic lethal, tumor formation
• Conditional knockout: Tissue-specific DNA repair deficiency
• Msh2 haploinsufficient: Cancer predisposition, impaired cognition

Mismatch Repair Mechanisms

The MSH2 protein functions as a core component of the mismatch repair (MMR) system, which corrects errors that escape the replication machinery's proofreading activity. MSH2 forms heterodimers with MSH6 (MutSα) and MSH3 (MutSβ) to recognize different types of mismatches.

MutSα Complex (MSH2-MSH6)

• Recognizes base-base mismatches and small insertion/deletion loops (1-2 nucleotides)
• Essential for maintaining replication fidelity
• Loss leads to microsatellite instability (MSI)

MutSβ Complex (MSH2-MSH3)

• Recognizes larger insertion/deletion loops (up to 10 nucleotides)
• Redundant but distinct functions with MutSα
• MSH3 deficiency leads to cancer predisposition in certain contexts

DNA Damage Response

Beyond mismatch repair, MSH2 participates in DNA damage response:

Recognition of DNA Lesions

• Detects modified bases and bulky adducts
• Triggers cell cycle arrest via ATM/ATR signaling
• Facilitates recruitment of repair proteins

Checkpoint Activation

• MSH2-dependent checkpoint response to UV damage
• phosphorylation by ATR/Chk1 pathway
• Transcriptional reprogramming for DNA repair

Cancer Associations

Lynch Syndrome

• MSH2 is one of the primary Lynch syndrome genes
• Germline mutations cause hereditary nonpolyposis colorectal cancer (HNPCC)
• MSH2 mutations account for ~30-40% of Lynch syndrome cases

Sporadic Cancers

• MSH2 deficiency common in colorectal, endometrial, gastric cancers
• Epigenetic silencing of MSH2 in some tumors
• Microsatellite instability (MSI-H) is a therapeutic biomarker

Therapeutic Implications

Immunotherapy

• MSI-H tumors respond to immune checkpoint inhibitors
• PD-1 blockade approved for MSH2-deficient cancers
• Tumor mutational burden correlates with response

Chemotherapy

• MSH2-deficient cells sensitive to alkylating agents
• Resistance to certain chemotherapias
• Combination strategies being explored

Animal Models

| Model | Phenotype | Key Findings |
|-------|-----------|--------------|
| Msh2 knockout mice | Embryonic lethal | Essential for development |
| Conditional knockout | Tumor prone | Lymphomas, gastrointestinal cancers |
| Knock-in mutants | Variable | Hypomorphic alleles inform function |

See Also

• [MSH6 Gene](/proteins/msh6-protein)
• [MLH1 Gene](/mlh1-gene)
• [DNA Damage Response Pathway](/mechanisms/dna-damage-response)
• [Oxidative Stress Pathway](/mechanisms/oxidative-stress-pathway)

External Links

• [NCBI Gene: MSH2](https://www.ncbi.nlm.nih.gov/gene/4439)
• [UniProt: MSH2](https://www.uniprot.org/uniprot/P43246)
• [CIViC: MSH2 variants](https://civicdb.org/variants/102)
• [PubMed Search: MSH2 neurodegeneration](https://pubmed.ncbi.nlm.nih.gov/?term=MSH2+neurodegeneration)

Background

The study of Msh2 — Muts Homolog 2 has evolved significantly over the past decades. Research in this area has revealed important insights into the underlying mechanisms of neurodegeneration and continues to drive therapeutic development.

Historical context and key discoveries in this field have shaped our current understanding and will continue to guide future research directions.

References

^[1] Edelmann W, et al. Cancer Res. 2000;60(4):983-989. PMID: 10706125(https://pubmed.ncbi.nlm.nih.gov/10706125/)

^[2] Yang J, et al. Nat Rev Cancer. 2021;21(10):645-661. PMID: 34341578(https://pubmed.ncbi.nlm.nih.gov/34341578/)

^[3] Shen J, et al. Nat Rev Neurosci. 2021;22(11):681-694. PMID: 34663971(https://pubmed.ncbi.nlm.nih.gov/34663971/)

^[4] Lovell MA, et al. J Neurosci Res. 2009;87(12):2776-2783. PMID: 19462462(https://pubmed.ncbi.nlm.nih.gov/19462462/)

^[5] Kennedy LJ, et al. Mutat Res. 2020;786-788:108318. PMID: 32246918(https://pubmed.ncbi.nlm.nih.gov/32246918/)

Pathway Diagram

The following diagram shows the key molecular relationships involving MSH2 — MutS Homolog 2 discovered through SciDEX knowledge graph analysis: