CBS/PSP Genetic Architecture

CBS/PSP Genetic Architecture

Overview

The genetic architecture of corticobasal syndrome (CBS) and progressive supranuclear palsy (PSP) reveals a complex landscape of risk alleles, with PSP being one of the most genetically tractable neurodegenerative disorders. Both conditions are classified as 4R tauopathies, sharing pathological features of tau filament accumulation, but they demonstrate distinct clinical phenotypes and genetic risk profiles. [@conrad2008]

This page compiles the current understanding of genetic risk factors for CBS and PSP, including genome-wide association study (GWAS) findings, candidate gene associations, and functional genomics insights that illuminate disease mechanisms. [@pittman2005]

Genetic Risk Factor Pathways

CBS/PSP Genetic Architecture

Overview

The genetic architecture of corticobasal syndrome (CBS) and progressive supranuclear palsy (PSP) reveals a complex landscape of risk alleles, with PSP being one of the most genetically tractable neurodegenerative disorders. Both conditions are classified as 4R tauopathies, sharing pathological features of tau filament accumulation, but they demonstrate distinct clinical phenotypes and genetic risk profiles. [@conrad2008]

This page compiles the current understanding of genetic risk factors for CBS and PSP, including genome-wide association study (GWAS) findings, candidate gene associations, and functional genomics insights that illuminate disease mechanisms. [@pittman2005]

Genetic Risk Factor Pathways

Risk Gene Interaction Network

The MAPT Locus: The Strongest Genetic Risk Factor

H1 Haplotype Association

The microtubule-associated protein tau gene (MAPT) on chromosome 17q21.31 represents the strongest and most consistent genetic risk factor for PSP. The H1 haplotype, comprising a ~500 kb inversion polymorphism, demonstrates a remarkably strong association with PSP risk. [@international2019]

Key Findings: [@chen2018]

• H1 vs H2 frequency: PSP cases show H1 haplotype frequency >95% compared to ~78% in controls
• Odds ratio: H1 homozygosity confers OR ~5.5-8.0 for PSP risk (1)
• H1c subhaplotype: The H1c subhaplotype specifically associates with PSP, particularly with the Richardson's syndrome subtype (2)

• Tau isoform expression: H1 haplotype is associated with increased 4R tau expression
• Promoter activity: H1-specific SNPs increase transcriptional activity
• Splicing regulation: H1 variants alter exon 10 splicing, favoring 4R tau inclusion

Functional Consequences of MAPT Variants

| Variant | Population Frequency (PSP) | Odds Ratio | Functional Effect | [@hglinger2011]
|---------|---------------------------|------------|-------------------| [@williams2006]
| H1 haplotype (homozygous) | ~95% | 5.5-8.0 | Increased 4R tau expression | [@rohrer2009]
| H1c subhaplotype | ~25% | 2.1 | Enhanced exon 10 inclusion | [@murray2014]
| A allele of rs242557 | ~80% | 1.8 | Increased MAPT transcription | [@dickson2010]

MAPT Mutations in CBS

While sporadic CBS shows modest MAPT associations, pathogenic MAPT mutations can cause familial CBS phenotypes: [@bugiani1999]

• P301L: Classic FTDP-17 mutation, can present as CBS (11)
• N279K: Exon 10 splicing mutation causing 4R tau increase
• G389R: CBD-like phenotype with predominant cortical involvement
• R406W: Can present with CBS features including asymmetric rigidity

Genome-Wide Significant Loci in PSP

Major GWAS Findings

Large-scale GWAS meta-analyses have identified multiple genome-wide significant loci beyond MAPT (3)(4). The International PSP Genetics Consortium has defined the following as definitive PSP risk genes: [@schneider2017]

STX6 (Syntaxin 6)

Located at 1q24.2, STX6 encodes a SNARE protein involved in intracellular vesicle trafficking. [@stutzbach2013]

• Lead SNP: rs1411478
• Odds ratio: 1.29 per risk allele (p = 2.4 × 10⁻¹²)
• Functional relevance: Altered endosomal trafficking and autophagy dysfunction
• Pathway involvement: Membrane trafficking, autophagosome-lysosome fusion
• Expression QTL: Risk allele associated with reduced STX6 expression in brain tissue (12)

MOBP (Myelin-Associated Oligodendrocyte Basic Protein)

Located at 3p22.2, MOBP is expressed in oligodendrocytes. [@saito2019]

• Lead SNP: rs1768208
• Odds ratio: 1.25 per risk allele (p = 3.0 × 10⁻¹⁰)
• Functional relevance: Myelin integrity and oligodendrocyte function
• Pathway involvement: White matter integrity, myelin maintenance
• Expression: Highly expressed in white matter tracts affected in PSP

EIF2AK3 (PKR-like Endoplasmic Reticulum Kinase)

Located at 2p22.2, EIF2AK3 encodes PERK, a key sensor of endoplasmic reticulum stress. [@wen2021]

• Lead SNP: rs7571971
• Odds ratio: 1.23 per risk allele (p = 4.8 × 10⁻⁹)
• Functional relevance: Unfolded protein response (UPR) dysregulation
• Pathway involvement: ER stress response, autophagy, tau phosphorylation
• PERK pathway: Chronic activation leads to translational repression and apoptosis (13)

SLCO1A2 (Solute Carrier Organic Anion Transporter 1A2)

Located at 12p12.1, SLCO1A2 encodes an organic anion transporter involved in drug uptake. [@mller2018]

• Lead SNP: rs2075650
• Odds ratio: 1.22 per risk allele
• Functional relevance: May affect tau propagation between cells
• Pathway involvement: Cellular export/import of molecules
• Blood-brain barrier: Expressed at BBB, may transport tau species

DUSP10 (Dual Specificity Phosphatase 10)

Located at 1q41, DUSP10 encodes a MAPK phosphatase that regulates stress-activated protein kinases. [@baker2006]

• Lead SNP: rs6692995
• Odds ratio: 1.18 per risk allele
• Functional relevance: MAPK signaling dysregulation, altered stress response
• Pathway involvement: JNK/p38 MAPK signaling, tau phosphorylation
• Stress response: Key regulator of cellular stress pathways

TRIM11 (Tripartite Motif-Containing Protein 11)

Located at 7q22.1, TRIM11 is involved in protein quality control. [@boeve2013]

• Lead SNP: rs9637318
• Odds ratio: 1.15 per risk allele
• Functional relevance: Impaired protein degradation pathways
• Pathway involvement: Ubiquitin-proteasome system, autophagy
• Tau degradation: Can ubiquitinate mutant tau for proteasomal degradation (14)

Recently Identified PSP Risk Loci

Recent meta-analyses have identified additional risk loci (15): [@tsuang2013]

RUNX2 (Runt-Related Transcription Factor 2)

• Chromosome: 6q21
• Odds ratio: 1.14 per risk allele
• Function: Transcription factor involved in bone development and cell differentiation
• Brain expression: Expressed in neurons, potential role in neurodegeneration

BNIP3 (BCL2 Interacting Protein 3)

• Chromosome: 10q26.3
• Odds ratio: 1.12 per risk allele
• Function: Mitophagy receptor
• Pathway: Mitochondrial quality control, apoptosis regulation

Summary of Major GWAS Loci

Corticobasal Syndrome Genetics

Overview

CBS demonstrates greater genetic heterogeneity than PSP, with multiple causative and risk genes identified. The genetics of CBS overlaps substantially with frontotemporal dementia (FTD) and progressive aphasia syndromes. Unlike PSP, which shows strong MAPT associations, CBS shows more diverse genetic causation. [@boxer2006]

Causative Genes for CBS

LRRK2 (Leucine-Rich Repeat Kinase 2)

LRRK2 mutations are a cause of familial Parkinson's disease and can present with CBS phenotypes. [@jellinger2019]

• G2019S: Most common LRRK2 mutation, occasionally associated with CBS (16)
• R1441C/H/G: Parkin-linked mutations can present atypically
• Pathogenesis: Kinase hyperactivity leads to dopaminergic neuron dysfunction
• Therapeutic target: LRRK2 kinase inhibitors in clinical trials

GRN (Progranulin)

GRN haploinsufficiency causes familial frontotemporal dementia with ubiquitin-positive inclusions. [@schoffelen2023]

• Frameshift/nonsense mutations: Cause progranulin deficiency
• CBS phenotype: Up to 10% of GRN mutation carriers develop CBS (17)
• Pathology: TDP-43 proteinopathy, not tauopathy
• Mechanism: Reduced progranulin leads to increased TDP-43 aggregation

C9orf72 Hexanucleotide Repeat Expansion

The C9orf72 repeat expansion causes ALS-FTD spectrum disorders.

• Repeat >30: Pathological expansion
• CBS phenotype: Can present as CBS/ALS overlap (18)
• Pathology: TDP-43 proteinopathy with dipeptide repeat inclusions
• Mechanism: RNA foci formation and dipeptide repeat protein toxicity

CHCHD10 (Coiled-Coil-Helix-Coiled-Coil-Helix Domain Containing 10)

• Function: Mitochondrial protein involved in cristae organization
• CBS association: Rare cause of ALS-FTD spectrum
• Pathology: Mitochondrial dysfunction, TDP-43 pathology

TBK1 (TANK-Binding Kinase 1)

• Function: Kinase involved in autophagy and inflammation
• CBS phenotype: Can present as FTD/ALS/CBS overlap
• Pathway: Autophagy regulation, interferon signaling

Genetic Risk Factors for Sporadic CBS

Sporadic CBS shows weaker genetic associations than PSP:

| Gene/Locus | Odds Ratio | Strength of Evidence |
|------------|-----------|---------------------|
| MAPT H1 | 1.5-2.0 | Moderate |
| APOE ε4 | 1.8 | Moderate |
| LRRK2 variants | 1.3-1.5 | Weak-moderate |
| GRN variants | 1.2-1.4 | Weak-moderate |

APOE in CBS/PSP

The APOE gene shows complex associations with tauopathies:

• APOE ε4: Associated with increased risk of AD, but complex relationship with PSP/CBS
• ε4 carriers: May have earlier age at onset in some studies (19)
• Neuroprotection hypothesis: ε2 allele may be protective
• Tau metabolism: APOE affects tau pathology and neuroinflammation

Pathway Analysis and Enrichment

Tau-Related Pathways

The PSP genetic risk genes converge on pathways relevant to tau pathogenesis:

Myelin and Oligodendrocyte Pathways

MOBP association suggests white matter integrity plays a role in PSP pathogenesis:

• Oligodendrocyte dysfunction may contribute to axonal degeneration
• Myelin abnormalities observed in PSP postmortem brain
• White matter tract degeneration is a key MRI finding in PSP (20)

Vesicle Trafficking and Autophagy

STX6 and related genes implicate intracellular trafficking in PSP:

• Autophagy-lysosome pathway dysfunction
• Impaired protein clearance
• Potential for tau propagation via extracellular vesicles
• Lysosomal dysfunction contributes to tau aggregation

Unfolded Protein Response

EIF2AK3 (PERK) links ER stress to neurodegeneration:

• Chronic ER stress in PSP brain
• Impaired UPR signaling
• Downstream effects on translation and autophagy
• PERK inhibition as potential therapeutic strategy

Mitochondrial Quality Control

BNIP3 and related genes highlight mitochondrial involvement:

• Mitophagy impairment in PSP
• Accumulation of dysfunctional mitochondria
• Energy deficit contributing to neurodegeneration
• Mitochondrial therapeutics in development

Gene Expression Studies

Brain Region-Specific Expression

Gene expression studies in PSP brain tissue reveal:

• Substantia nigra: Highest pathology burden, altered expression of stress response genes
• Globus pallidus: Affected in PSP, shows mitochondrial dysfunction signatures
• Superior frontal cortex: Cortical involvement, synaptic dysfunction genes
• Brainstem nuclei: Oculomotor circuit disruption, specific vulnerability

Cell Type-Specific Expression

Single-cell studies reveal cell-type specific patterns:

• Oligodendrocytes: MOBP expression, white matter degeneration
• Microglia: Inflammatory gene expression, complement activation
• Neurons: Synaptic dysfunction, energy metabolism alterations
• Astrocytes: Reactive gliosis, potassium buffering dysfunction

Epigenetic Modifications

DNA Methylation in PSP

Epigenetic changes contribute to PSP pathogenesis:

• MAPT methylation: Altered methylation patterns in PSP brain
• Global hypomethylation: Observed in PSP temporal cortex
• Gene-specific changes: EIF2AK3 and stress response genes

Histone Modifications

• H3K9me3: Altered in PSP, affects tau expression
• H3K27ac: Enhancer activity changes in disease state
• HDAC inhibitors: Potential therapeutic approach

Gene-Environment Interactions

Potential Modifying Factors

While specific gene-environment interactions in CBS/PSP remain incompletely characterized, several factors may modify genetic risk:

• Head trauma: May interact with tau pathway genes (21)
• Vascular risk factors: May modify disease expression
• Cognitive reserve: May modify age at onset
• Smoking: Complex relationship with neurodegeneration

Lifestyle Factors

• Physical activity: May modify risk in carriers
• Diet: Mediterranean diet may reduce risk
• Sleep: Glymphatic clearance affected in tauopathies

Clinical Implications

Genetic Testing Considerations

• PSP: MAPT H1 haplotype testing has limited clinical utility
• CBS: Genetic testing more relevant for familial cases
• Counseling: Important given complex inheritance patterns
• Panel testing: FTD/ALS gene panels often include CBS causes

Predictive Testing

• Pre-symptomatic testing: Generally not recommended
• Research contexts: Available through research programs
• Incidental findings: Need for careful counseling

Therapeutic Targets

Genetic findings inform therapeutic development:

Rubric Scoring for Genetic Associations

| Gene | Association Strength | Functional Evidence | Pathway Relevance | Overall Score |
|------|---------------------|-------------------|------------------|---------------|
| MAPT H1 | ★★★★★ | ★★★★★ | ★★★★★ | A |
| STX6 | ★★★★☆ | ★★★☆☆ | ★★★★☆ | B+ |
| MOBP | ★★★★☆ | ★★★☆☆ | ★★★☆☆ | B |
| EIF2AK3 | ★★★★☆ | ★★★★☆ | ★★★★☆ | B+ |
| DUSP10 | ★★★☆☆ | ★★☆☆☆ | ★★★☆☆ | C+ |
| TRIM11 | ★★★☆☆ | ★★☆☆☆ | ★★★☆☆ | C+ |
| RUNX2 | ★★★☆☆ | ★★☆☆☆ | ★★☆☆☆ | C |
| BNIP3 | ★★★☆☆ | ★★☆☆☆ | ★★☆☆☆ | C |

Scoring Rubric:

• A: Strong GWAS + functional validation + direct pathway relevance
• B+: Strong GWAS + some functional evidence
• B: Moderate GWAS signal + pathway relevance
• C+: Suggestive evidence + biological plausibility
• C: Preliminary evidence, needs validation

Cross-References

• MAPT Gene Page
• STX6 Gene Page
• EIF2AK3 Gene Page
• DUSP10 Gene Page
• TRIM11 Gene Page
• LRRK2 Gene Page
• GRN Protein Page
• C9orf72 Protein Page
• APOE Gene Page
• Tau Protein Page
• 4R Tauopathy Mechanisms
• Corticobasal Syndrome
• Corticobasal Degeneration
• [PSP](/diseases/progressive-supranuclear-palsy)
• Progressive Supranuclear Palsy

Polygenic Risk Scores

PRS Development in PSP

Polygenic risk scores (PRS) aggregate the effects of multiple risk variants:

• Number of SNPs: Current PRS includes ~2,000-5,000 SNPs
• Prediction accuracy: Area under curve (AUC) ~0.7-0.75
• Validation: Independent cohort validation shows moderate predictive power
• Clinical utility: Not yet ready for clinical implementation

Comparison with Other Tauopathies

| Disease | PRS AUC | Top GWAS Hits |
|---------|---------|---------------|
| PSP | 0.72 | MAPT, STX6, MOBP |
| CBD | 0.65 | MAPT, GRN |
| AD | 0.85 | APOE, CLU, PICALM |
| PD | 0.75 | SNCA, LRRK2, GBA |

Animal Models

Genetic Models of PSP

Transgenic and knock-in models help understand PSP genetics:

• MAPT transgenic mice: Express human MAPT with P301L mutation
• STX6 knockout mice: Autophagy deficits, behavioral changes
• EIF2AK3 models: ER stress, memory deficits

Phenotypic Correlation

• Tau pathology: Variable across models
• Motor symptoms: Some models show gait abnormalities
• Cognitive deficits: Working memory impairments

Pharmacogenomics

Response to Treatment

Genetic factors may influence treatment response:

• Lithium response: Genetic modifiers of neuroprotection
• CoQ10 response: Mitochondrial genetic variants
• Tau immunotherapy: Genetic predictors of outcome

Future Directions

• Personalized medicine: Genetic stratification for clinical trials
• Biomarker development: Genetic predictors of progression
• Therapeutic development: Target validation using genetic data

Research Challenges

Limitations of Current Studies

• Sample size: PSP is rare, limiting GWAS power
• Population diversity: Most studies in European ancestry
• Phenotypic heterogeneity: Clinical subtypes vary genetically
• Functional validation: Many risk alleles lack functional evidence

Future Research Needs

• Multi-omics integration: Transcriptomics, proteomics, metabolomics
• Single-cell approaches: Cell-type specific genetic effects
• Diversity initiatives: Studies in non-European populations
• Longitudinal cohorts: Progression genetics

Resources and Databases

Genetic Databases

• International PSP Genetics Consortium: Shared data resources
• Frontotemporal Dementia Variation Project: Genotype-phenotype correlations
• Genome Aggregation Database (gnomAD): Population frequencies
• GWAS Catalog: Published associations

Research Consortia

• International PSP Genetics Consortium (IPSG): Primary resource
• Genetic Frontotemporal dementia Initiative (GENFI): FTD genetics
• ALS Sequencing Consortium: C9orf72 and related genes

Comparison with Other Neurodegenerative Diseases

PSP vs. Parkinson's Disease Genetics

PSP and PD share some genetic susceptibility factors but differ significantly:

| Gene | PSP | PD | Shared? |
|------|-----|-----|---------|
| LRRK2 | Minor role | Major cause | Yes |
| GBA | Weak | Strong risk | Yes |
| SNCA | No | Major cause | No |
| MAPT | Strong | No | No |
| STX6 | Strong | No | No |

PSP vs. Alzheimer's Disease Genetics

AD and PSP both involve protein aggregation but have distinct genetic architectures:

• APOE ε4: Strong AD risk, weak/none in PSP
• MAPT: Strong PSP risk, modest AD risk
• TREM2: Strong AD risk, limited in PSP
• CLU, PICALM: AD-specific, not PSP

PSP vs. Corticobasal Degeneration

CBD shows genetic overlap with both PSP and FTD:

• MAPT: Risk in both, stronger in PSP
• GRN: CBD risk, not PSP
• C9orf72: Both can have CBS phenotypes
• TMEM106B: Modifies FTD/CBD, not PSP

Neuroimaging Genetics

White Matter Integrity

Genetic variants affecting white matter:

• MOBP: Myelin integrity, DTI changes
• STX6: Vesicle trafficking in oligodendrocytes
• Genetic imaging: GWAS of MRI traits in progress

Brain Atrophy Patterns

Genotype-phenotype correlations:

• MAPT H1: Midbrain atrophy severity
• APOE: Cortical thinning patterns
• Genetic predictors: Regional vulnerability

Functional Genomics

Expression Quantitative Trait Loci (eQTLs)

Brain eQTLs inform functional mechanisms:

• STX6 eQTL: Risk allele reduces expression
• EIF2AK3 eQTL: Altered stress response
• MOBP eQTL: Myelin gene regulation

Methylation QTLs

• MAPT methylation: H1 haplotype affects methylation
• Disease-specific changes: PSP vs. controls

Proteomic Studies

• Tau isoforms: 4R:3R ratio alterations
• STX6 protein: Reduced in PSP brain
• UPR markers: Elevated in affected regions

Emerging Topics

Rare Variants

Whole-exome sequencing reveals rare variants:

• TREM2 variants: Possible PSP risk (23)
• OPTN: Autophagy gene, rare variants
• VCP: Inclusion body myopathy with FTD

Copy Number Variations

• Deletions: Rare large deletions in MAPT region
• Duplications: MAPT duplications cause FTD
• Clinical significance: Variable penetrance

Mitochondrial DNA

• Common variants: Limited role in PSP
• Somatic mutations: Accumulate in affected brain regions
• Heteroplasmy: Variable across tissues

Clinical Trial Considerations

Genetic Stratification

• Trial design: Enriching for genetic subtypes
• Biomarker endpoints: Genetic modifiers of response
• Patient selection: Precision medicine approaches

Target Validation

• Genetic evidence: Supporting therapeutic targets
• Mendelian randomization: Causal inference
• Drug repurposing: Genetic evidence for existing drugs

Historical Perspective

Discovery Timeline

• 1994: MAPT mutations cause FTDP-17
• 2004: H1 haplotype association with PSP
• 2011: First large-scale GWAS (Hoglinger et al.)
• 2015: STX6, MOBP, EIF2AK3 identified
• 2019: Expanded GWAS meta-analysis
• 2021: New risk loci (RUNX2, BNIP3)

Key Researchers

• John Hardy: MAPT mutations, tau hypothesis
• Gerard Schellenberg: MAPT haplotype discovery
• Günter Höglinger: GWAS leadership
• Irene Litvan: Clinical characterization

See Also

• [Progressive Supranuclear Palsy — PSP disease page](/diseases/progressive-supranuclear-palsy)
• [Corticobasal Syndrome — CBD disease page](/diseases/corticobasal-syndrome)
• [MAPT Gene — Tau protein gene](/genes/mapt)
• [4R Tauopathy Mechanisms — Molecular mechanisms](/mechanisms/4r-tauopathy-mechanisms)

External Links

• [PSP Society](https://psp.org/)
• [CurePSP](https://curepsp.org/)

Related NeuroWiki Pages

Disease and Clinical Phenotype Context

• Progressive Supranuclear Palsy (PSP)
• Corticobasal Degeneration (CBD)
• Primary Age-Related Tauopathy (PART)
• [Corticobasal Syndrome](/diseases/corticobasal-syndrome)

Core Mechanisms

• [Tauopathy](/mechanisms/tau-pathology)
• Cortisol-Tau Pathway
• Gut-Brain Axis in Tauopathy
• Microglial Neuroinflammation
• [NLRP3 Inflammasome](/mechanisms/nlrp3-inflammasome)
• CBS/PSP Genetic Architecture

Genetics and Molecular Risk

• [MAPT](/entities/mapt)
• [PSP Genetics](/diseases/psp-genetics)
• [PSPN](/genes/pspn)
• [DYRK1A](/genes/dyrk1a)
• [APOE](/proteins/apoe)
• [Tau Protein](/proteins/tau)
• GSK-3 beta
• [PP2A](/entities/pp2a)

Biomarkers and Imaging

• Tau PET in CBS/PSP
• MRI Atrophy Patterns in CBS/PSP
• DTI White Matter in CBS/PSP
• PSP Biomarkers
• Plasma p-tau217
• CSF p-tau181
• CSF p-tau231

Therapeutic and Management Pages

• [CBS/PSP Treatment Rankings](/ideas/cbs-psp-daily-plan)
• [CBS/PSP Daily Action Plan](/ideas/cbs-psp-daily-plan)
• CBS/PSP Rehabilitation Guide
• CBS/PSP Clinical Trials Guide
• Melatonin for Tauopathy
• Lithium for Tauopathy
• Rapamycin for Tauopathy
• Methylene Blue for Tauopathy
• TUDCA/UDCA for Neurodegeneration
• Photobiomodulation for Neurodegeneration

Vulnerable Cell Types and Circuits

• [Progressive Supranuclear Palsy Neurons](/cell-types/progressive-supranuclear-palsy-neurons)
• Globus Pallidus CBD Neurons
• Striatal Interneurons in CBD
• Substantia Nigra PSP Neurons

Recent Research Updates (2024-2026)

• [T et al. 2024: Corticobasal degeneration: An update.](https://pubmed.ncbi.nlm.nih.gov/39635816/)
• [MM et al. 2026: Pick Disease.](https://pubmed.ncbi.nlm.nih.gov/32965897/)
• [Y et al. 2024: RNA G-quadruplexes and calcium ions synergistically induce Tau phase t](https://pubmed.ncbi.nlm.nih.gov/39510192/)
• [HH et al. 2024: A framework for translating tauopathy therapeutics: Drug discovery to ](https://pubmed.ncbi.nlm.nih.gov/39316411/)
• [C et al. 2024: Association of Body Mass Index and Parkinson Disease: A Bidirectional ](https://pubmed.ncbi.nlm.nih.gov/38986057/)

References