Genome-wide association studies (GWAS) have revolutionized our understanding of the genetic architecture of neurodegenerative diseases. Unlike rare causative mutations that cause familial forms, GWAS identifies common genetic variants with modest effect sizes that influence disease risk, age at onset, and progression. This hub synthesizes major GWAS findings for Alzheimer's disease (AD) and Parkinson's disease (PD), mapping risk loci to biological pathways and therapeutic targets.
GWAS for neurodegenerative diseases employ case-control designs with increasingly large cohorts. The International Genomics of Alzheimer's Project (IGAP) and Parkinson's Disease Genetics Consortium (PDGC) have identified dozens of risk loci through meta-analyses of tens of thousands of cases and controls.
Key methodological considerations:
| Gene/Region | Chromosome | Odds Ratio | Pathway | Function |
|---|---|---|---|---|
| APOE | 19q13.32 | 3.5-4.0 (ε4) | Lipid metabolism, Aβ clearance | Cholesterol transport, amyloid binding |
| TREM2 | 6p21.1 | 2.6-4.5 | Neuroinflammation, microglia | Triggering receptor on myeloid cells |
| BIN1 | 2q14.3 | 1.2-1.3 | Synaptic function, endocytosis | Bridging integrator 1, tau biology |
| CLU | 8p21.1 | 1.1-1.2 | Protein homeostasis | Clusterin, complement regulation |
| PICALM | 10q24.3 | 1.1-1.2 | Endocytosis, autophagy | Phosphatidylinositol binding |
| CR1 | 1q32.1 | 1.1-1.2 | Neuroinflammation | Complement receptor 1 |
| CD33 | 19q13.41 | 1.1-1.2 | Neuroinflammation | Sialic acid receptor on microglia |
| ABCA7 | 19p13.3 | 1.1-1.2 | Lipid metabolism | ATP-binding cassette transporter |
| PTK2B | 8p21.2 | 1.1 | Synaptic plasticity | Protein tyrosine kinase |
| SORL1 | 11q24.1 | 1.1-1.3 | APP processing | Sortilin-related receptor |
| MEF2C | 5q14.3 | 1.1 | Synaptic plasticity | Myocyte enhancer factor 2C |
| NME8 | 7p31.3 | 1.1 | Axonal function | NM23-H8, sphingolipid metabolism |
| RIN3 | 14q32.12 | 1.1 | Endocytosis | Ras and Rab interactor 3 |
| INPP5D | 2q37.1 | 1.1 | Neuroinflammation | SHIP1, microglial signaling |
| MADD/SPI1 | 11p11.2 | 1.1 | Apoptosis, microglia | SPI1 regulates microglial genes |
AD GWAS loci converge on several key biological pathways:
1. Lipid Metabolism and Cholesterol Transport
2. Microglial Activation and Neuroinflammation
3. Endocytic and Synaptic Function
4. Protein Homeostasis and APP Processing
Recent meta-analyses (IGAP 2019) identified 29 risk loci explaining ~7.7% of SNP heritability. Remaining heritability may reside in rare variants detectable only through sequencing studies.
| Gene/Region | Chromosome | Odds Ratio | Pathway | Function |
|---|---|---|---|---|
| GBA | 1q21 | 2.0-5.0 | Lysosomal function | Glucocerebrosidase, α-syn clearance |
| SNCA | 4q21 | 1.3-1.5 | Protein aggregation | α-synuclein, Lewy body formation |
| LRRK2 | 12q12 | 1.3-2.0 | Protein kinase signaling | Leucine-rich repeat kinase 2 |
| MAPT | 17q21.31 | 1.2-1.4 | Cytoskeleton, tau | Microtubule-associated protein tau |
| PARK16 | 1q32 | 1.3 | Endoplasmic reticulum | ER stress, lipid metabolism |
| BST1 | 4p15 | 1.2 | Calcium signaling | Bone stromal cell antigen |
| SNCA (repeat) | 4q21 | 1.4-1.8 | α-syn propagation | Multiplication leads to PD |
| GCH1 | 14q22 | 1.2 | Dopamine synthesis | GTP cyclohydrolase 1 |
| DR2 (Parkinson) | 11q13 | 1.2 | Dopamine signaling | Dopamine receptor D2 |
| VPS35 | 16q11 | 1.5-2.0 | Endosomal trafficking | Vacuolar protein sorting 35 |
| DNAJC13 | 3q22 | 1.3 | Endosomal function | Co-chaperone |
| OR4K2 | 5q33 | 1.2 | Olfactory function | May relate to olfactory loss |
| CCDC62 | 5q35 | 1.2 | Vesicle trafficking | HIV-1 interaction protein |
| STX1B | 16p12 | 1.1 | Synaptic transmission | Syntaxin 1B |
| FAM47E | 4p14 | 1.1 | Unknown | Function unclear |
PD GWAS reveals distinct mechanistic clusters:
1. Lysosomal and Autophagy Pathways
2. Protein Aggregation and Homeostasis
3. Mitochondrial Function
4. Neuroinflammation
5. Dopamine Metabolism
PD GWAS (Nalls et al. 2019, 2014) identified 90+ risk loci explaining ~16-22% of SNP heritability. Unlike AD, PD shows strong monogenic forms (LRRK2, SNCA, GBA) that inform biological pathways.
Several genetic loci and pathways are shared between AD and PD:
1. Neuroinflammation
2. Lipid Metabolism
3. Endolysosomal Function
4. Protein Aggregation
GWAS findings directly inform drug development:
| GWAS Target | Therapeutic Approach | Status |
|---|---|---|
| TREM2 | Agonist antibodies (AL002) | Phase 2 for AD |
| APOE | Gene therapy, apoE mimetics | Preclinical |
| LRRK2 | Inhibitors (DNL151, BIIB122) | Phase 2 for PD |
| GBA | Substrate reduction therapy | Phase 2 for PD |
| SNCA | Immunotherapy (prasinezumab) | Phase 2 for PD |
| BIN1 | Tau-targeting | Preclinical |
GWAS enables polygenic risk scores (PRS) that: