The Genetics of Parkinson’s Disease
A comprehensive, academically cited review of every gene implicated in Parkinson’s disease — from rare monogenic forms to common GWAS risk loci, genetic testing, gene therapy, and precision medicine.
1. Introduction to Parkinson’s Disease Genetics
Parkinson’s disease (PD) is the second most common progressive neurodegenerative disorder, affecting approximately 1-2% of the population over age 65, with prevalence rising to 4-5% in those over 85 (de Lau & Breteler, The Lancet Neurology, 2006). While the majority of cases are classified as idiopathic or sporadic, the genetic architecture of PD has been progressively elucidated over the past three decades, revealing a complex interplay between rare high-penetrance mutations, common low-effect risk variants, and environmental factors.
The genetic landscape of PD can be broadly categorized as follows:
- Monogenic (single-gene) forms account for approximately 5-10% of all PD cases and explain roughly 30% of familial cases and 3-5% of sporadic cases (Klein & Westenberger, Cold Spring Harbor Perspectives in Medicine, 2012).
- Common genetic risk variants identified through genome-wide association studies (GWAS) now number over 134 loci, with 90+ independently confirmed (Global Parkinson’s Genetics Program [GP2], 2025).
- GBA1 and LRRK2 variants together represent the most frequently identified genetic factors, found in approximately 10-15% of genetically tested PD patients (Parkinson’s Foundation PD GENEration, Alcalay et al., Brain, 2024).
The genes implicated in PD converge on several major cellular pathways: mitochondrial quality control, lysosomal function, vesicle trafficking and endosomal sorting, alpha-synuclein proteostasis, immune and inflammatory signaling, and synaptic function (Blauwendraat et al., The Lancet Neurology, 2020).
2. Autosomal Dominant Genes
2.1 SNCA (Alpha-Synuclein) — PARK1/PARK4
| Property | Details |
|---|---|
| Chromosome | 4q22.1 |
| Inheritance | Autosomal dominant |
| Protein | Alpha-synuclein (140 amino acids, presynaptic neuronal protein) |
| PARK Locus | PARK1 (missense mutations) / PARK4 (genomic multiplications) |
Mechanism: Alpha-synuclein is the principal protein constituent of Lewy bodies, the neuropathological hallmark of PD. Missense mutations — including A53T, A30P, E46K, H50Q, G51D, and A53E — alter protein folding and promote pathological aggregation. Gene duplications and triplications increase protein dosage, with a clear dose-response relationship: triplications cause earlier onset (typically in the fourth decade) with rapid progression and dementia, while duplications more closely resemble late-onset idiopathic PD (Singleton et al., Science, 2003; Chartier-Harlin et al., The Lancet, 2004).
Historical significance: SNCA was the first PD gene identified, discovered in 1997 by Polymeropoulos and colleagues in Italian-Greek kindreds carrying the A53T mutation (Polymeropoulos et al., Science, 1997). This landmark discovery established the genetic basis of PD and placed alpha-synuclein at the center of PD pathogenesis research.
Population specificity: SNCA missense mutations remain rare overall. The A53T variant was originally identified in Italian and Greek families. SNCA is also the most significant common genetic risk locus for sporadic PD identified in GWAS (Nalls et al., The Lancet Neurology, 2019).
2.2 LRRK2 (Leucine-Rich Repeat Kinase 2) — PARK8
| Property | Details |
|---|---|
| Chromosome | 12q12 (51 exons) |
| Inheritance | Autosomal dominant with incomplete penetrance |
| Protein | Dardarin (2,527 amino acids; dual kinase and GTPase activities) |
| PARK Locus | PARK8 |
Mechanism: LRRK2 is a large multidomain protein kinase involved in vesicle trafficking, autophagy, mitochondrial function, immune signaling, and cytoskeletal dynamics. The G2019S mutation — the most common pathogenic variant — results in increased kinase activity. LRRK2 is highly expressed in immune cells (monocytes, B cells, microglia) and plays a critical role in innate immunity and neuroinflammation. Mutant LRRK2 enhances alpha-synuclein aggregation, phosphorylates RAB GTPases, and interacts with the PINK1/Parkin mitophagy pathway (Healy et al., The Lancet Neurology, 2008; Steger et al., eLife, 2016).
Prevalence: LRRK2 G2019S is the most common known cause of monogenic PD, accounting for 1-2% of sporadic PD and 3-6% of familial dominant PD in European populations. Penetrance is estimated at 25-42.5% by age 80, modified by polygenic risk scores (Lee et al., Movement Disorders, 2017; Biernacka et al., The Lancet Neurology, 2024).
Population specificity:
- North African Berber/Arab: Approximately 30-41% of PD cases carry G2019S; the highest known carrier frequency (1 in 30) among healthy Moroccan Berbers (Lesage et al., The New England Journal of Medicine, 2006).
- Ashkenazi Jewish: 15-30% of familial PD, ~6% of sporadic PD; shared common founder from approximately the 2nd century CE (Ozelius et al., The New England Journal of Medicine, 2006).
- Basque: G2019S and R1441G mutations are common in this population.
- Asian populations: Very rare (<0.01%) (Tan et al., Human Mutation, 2019).
Clinical features: Late-onset (median 56 years), clinically resembles idiopathic PD. Slowly progressive, predominantly motor subtype with relatively fewer non-motor symptoms including less hyposmia, less REM sleep behavior disorder, and less cognitive impairment compared to idiopathic PD (Marras et al., Movement Disorders, 2016).
2.3 VPS35 (Vacuolar Protein Sorting 35) — PARK17
| Property | Details |
|---|---|
| Chromosome | 16q11.2 |
| Inheritance | Autosomal dominant |
| Protein | VPS35; core component of the retromer complex |
| PARK Locus | PARK17 |
Mechanism: VPS35 is essential for endosomal protein sorting and recycling via the retromer complex. The D620N mutation — the only confirmed pathogenic variant — disrupts cargo sorting, impairs WASH complex recruitment, reduces alpha-synuclein degradation, causes mitochondrial fragmentation, and can induce LRRK2 hyperactivation (Vilariño-Güell et al., American Journal of Human Genetics, 2011; Zimprich et al., American Journal of Human Genetics, 2011).
Clinical features: Median onset approximately 50 years. Clinically indistinguishable from idiopathic PD but generally milder course with good levodopa response. Found in both familial and rare sporadic cases worldwide at very low frequency.
3. Autosomal Recessive Genes
3.1 PRKN / Parkin — PARK2
| Property | Details |
|---|---|
| Chromosome | 6q25.2-q27 (12 exons; one of the largest human genes) |
| Inheritance | Autosomal recessive |
| Protein | Parkin; an E3 ubiquitin ligase |
| PARK Locus | PARK2 |
Mechanism: Parkin functions as an E3 ubiquitin ligase that works cooperatively with PINK1 in mitochondrial quality control. When PINK1 accumulates on damaged mitochondria, it phosphorylates and recruits Parkin, which ubiquitinates outer mitochondrial membrane proteins to initiate mitophagy — the selective clearance of damaged mitochondria (Narendra et al., The Journal of Cell Biology, 2008; Matsuda et al., The Journal of Cell Biology, 2010).
Prevalence: The most common known cause of autosomal recessive early-onset PD, accounting for approximately 50% of autosomal recessive parkinsonism in Europe, up to 42.2% of cases with onset at age 20 or younger, and approximately 18% of simplex cases with onset before age 45. Estimated genetic prevalence: 22 per 100,000 in non-Finnish Europeans (Lubbe et al., medRxiv, 2024). Originally described in Japanese families in the 1970s as autosomal recessive juvenile parkinsonism (Kitada et al., Nature, 1998).
Clinical features: Onset before age 40 (median 31 years, range 3-81 years), sometimes juvenile onset (<20 years). Characterized by foot dystonia, sleep benefit, slow progression, and excellent sustained levodopa response.
3.2 PINK1 (PTEN-Induced Putative Kinase 1) — PARK6
| Property | Details |
|---|---|
| Chromosome | 1p36.12 |
| Inheritance | Autosomal recessive |
| Protein | PINK1; a 581-amino acid mitochondrial serine/threonine kinase |
| PARK Locus | PARK6 |
Mechanism: PINK1 senses mitochondrial damage. In healthy mitochondria, PINK1 is imported and rapidly degraded. When mitochondria are damaged (loss of membrane potential), PINK1 accumulates on the outer mitochondrial membrane, where it phosphorylates ubiquitin and Parkin, activating Parkin’s E3 ligase activity and initiating mitophagy (Valente et al., Science, 2004). A major breakthrough in 2025 resolved the human PINK1 protein structure for the first time, revealing the molecular mechanism of its activation (Kumar et al., Nature, 2025). Over 70 pathogenic PINK1 variants have been identified.
Clinical features: Early onset, clinically indistinguishable from Parkin-linked PD, with slow progression and good levodopa response. More frequent psychiatric symptoms (depression, anxiety, psychosis) compared to idiopathic PD.
3.3 DJ-1 — PARK7
| Property | Details |
|---|---|
| Chromosome | 1p36.23 |
| Inheritance | Autosomal recessive |
| Protein | DJ-1 (Parkinsonism-associated deglycase); 189 amino acids, homodimer |
| PARK Locus | PARK7 |
Mechanism: DJ-1 is a multifunctional protein involved in sensing and protecting against oxidative stress, maintaining mitochondrial homeostasis (membrane potential, ATP production, complex I assembly), chaperone-mediated autophagy, dopamine homeostasis, and repair of methylglyoxal-glycated nucleotides. DJ-1 operates in a pathway parallel to PINK1/Parkin (Bonifati et al., Science, 2003).
Prevalence: The rarest of the three established autosomal recessive PD genes. Accounts for a small fraction of early-onset recessive PD worldwide.
4. Genes Causing Atypical/Complex Parkinsonism
These genes cause forms of parkinsonism that frequently present with additional neurological features beyond classic PD.
| Gene | PARK Locus | Chromosome | Inheritance | Clinical Syndrome |
|---|---|---|---|---|
| ATP13A2 | PARK9 | 1p36.13 | AR | Kufor-Rakeb syndrome — juvenile-onset with dementia, supranuclear gaze palsy, spasticity (Ramirez et al., Nature Genetics, 2006) |
| PLA2G6 | PARK14 | 22q13.1 | AR | Adult-onset dystonia-parkinsonism; also causes infantile neuroaxonal dystrophy (Paisan-Ruiz et al., Brain, 2009) |
| FBXO7 | PARK15 | 22q12.3 | AR | Early-onset parkinsonian-pyramidal syndrome with spasticity (Shojaee et al., Neurology, 2008) |
| DNAJC6 | PARK19 | 1p31.3 | AR | Juvenile atypical parkinsonism; auxilin deficiency disrupts synaptic vesicle recycling (Edvardson et al., PLOS ONE, 2012) |
| SYNJ1 | PARK20 | 21q22.11 | AR | Parkinsonism with poor levodopa response, dystonia, seizures (Krebs et al., PLOS Genetics, 2013) |
| DCTN1 | — | 2p13.1 | AD | Perry syndrome — parkinsonism with depression, weight loss, central hypoventilation (Farrer et al., Nature Genetics, 2009) |
| RAB39B | — | Xq28 | X-linked | Early-onset parkinsonism with intellectual disability and Lewy body pathology (Wilson et al., American Journal of Human Genetics, 2014) |
5. Recently Implicated Genes (Awaiting Independent Replication)
These genes have been reported in PD families but have not yet been robustly replicated across independent studies. Their pathogenicity remains debated in the literature.
| Gene | PARK Locus | Chromosome | Inheritance | Status |
|---|---|---|---|---|
| CHCHD2 | PARK22 | 7p11.2 | AD | Variants largely in East Asian populations; replication limited |
| VPS13C | PARK23 | 15q22.2 | AR | Stronger evidence; loss of function causes mitochondrial dysfunction (Lesage et al., Nature Genetics, 2016) |
| TMEM230 | — | 20p12.3 | AD | Independent replication has largely failed in Caucasian populations |
| LRP10 | — | 14q11.2 | AD | Under investigation; initial family report pending confirmation |
| EIF4G1 | PARK18 | 3q27.1 | AD | Not independently replicated |
| UCHL1 | PARK5 | 4p13 | AD | Single family; common variants may modify risk |
6. Genetic Risk Factor Genes
6.1 GBA1 (Glucocerebrosidase) — The Most Common Genetic Risk Factor
| Property | Details |
|---|---|
| Chromosome | 1q21.1 (pseudogene GBAP located 6.9 kb downstream) |
| Inheritance | Complex: heterozygous variants act as risk factors (20-30x increased risk); homozygous/compound heterozygous mutations cause Gaucher disease |
| Protein | Glucocerebrosidase (GCase); lysosomal hydrolase (497 amino acids) |
Mechanism: GBA1 variants contribute to PD through multiple interconnected mechanisms: (1) reduced GCase activity impairs lysosomal degradation of glucosylceramide, leading to substrate accumulation and impaired alpha-synuclein clearance; (2) misfolded GCase triggers ER stress and the unfolded protein response; (3) GCase deficiency promotes alpha-synuclein aggregation while alpha-synuclein reciprocally inhibits GCase activity, creating a pathogenic feedback loop; and (4) disrupted autophagy-lysosomal pathway (Sidransky et al., The New England Journal of Medicine, 2009; Mazzulli et al., Cell, 2011).
Prevalence: Found in 5-20% of PD patients depending on population and sequencing depth. Variants classified as “severe” (associated with type II/III Gaucher disease) confer higher PD risk and earlier onset than “mild” variants (type I Gaucher disease).
Population specificity:
- Ashkenazi Jewish: Highest prevalence worldwide — 18-31% of PD patients carry GBA1 variants. The most common variant is p.N370S. Gaucher disease carrier frequency in this population is approximately 6% (Aharon-Peretz et al., The New England Journal of Medicine, 2004).
- Non-Ashkenazi populations: p.E326K is the most common PD-associated variant globally.
Therapeutic relevance: At least six ongoing clinical trials specifically recruit GBA-PD patients. Therapeutic strategies include GCase enzyme enhancement (ambroxol), substrate reduction therapy, and gene therapy (AAV9-GBA1) (Mullin et al., JAMA Neurology, 2020).
Other genetic risk factor genes: TMEM175 (lysosomal K+/H+ channel, chromosome 4p16.3), SCARB2 (GCase transport receptor, chromosome 4q21.1), and SMPD1 (acid sphingomyelinase, chromosome 11p15.4) further underscore the central role of lysosomal dysfunction in PD pathogenesis.
7. GWAS Susceptibility Loci
The largest PD genome-wide association study to date (GP2, 2025) identified 134 loci, of which 59 are novel. A 2024 multi-ancestry meta-analysis encompassing 49,049 cases, 18,785 proxy cases, and 2,458,063 controls identified 78 independent genome-wide significant loci including 12 potentially novel loci (Nalls et al., The Lancet Neurology, 2019; Kim et al., Nature Genetics, 2024).
| Gene/Locus | Chromosome | Function |
|---|---|---|
| SNCA | 4q22.1 | Alpha-synuclein; strongest GWAS signal for sporadic PD |
| MAPT | 17q21.31 | Microtubule-associated protein tau; H1 haplotype increases PD risk |
| HLA-DRB5 | 6p21.32 | MHC class II antigen; immune function and neuroinflammation |
| BST1 | 4p15.32 | Bone marrow stromal cell antigen; immune cell proliferation |
| GAK | 4p16.3 | Cyclin G-associated kinase; clathrin-mediated endocytosis |
| TMEM175 | 4p16.3 | Lysosomal K+/H+ channel; lysosomal pH regulation |
| RIT2 | 18q12.3 | Ras-like protein 2; neuronal signaling |
| BAG3 | 10q26.11 | Chaperone-assisted selective autophagy |
| FYN | 6q21 | Tyrosine kinase; tau phosphorylation, alpha-synuclein signaling |
| NOD2 | 16q12.1 | Innate immunity; shared risk locus with Crohn’s disease |
| CTSB | 8p23.1 | Cathepsin B; lysosomal protease |
| GPNMB | 7p15.1 | Glycoprotein NMB; lysosomal/immune function |
| RAB7L1 | 1q32 | RAB GTPase; vesicle trafficking; interacts with LRRK2 |
Novel loci from the 2024 multi-ancestry meta-analysis include MTF2, PIK3CA, ADD1, SYBU, IRS2, USP8, PIGL, FASN, MYLK2, USP25, EP300, and PPP6R2 (Kim et al., Nature Genetics, 2024).
8. Immune and Neuroinflammation Genes
The immune/inflammatory pathway is increasingly recognized as central to PD pathogenesis. Key genetic evidence includes:
- HLA region (6p21.32): Common variants in HLA-DRB5/DRA are robustly associated with PD risk. HLA-DR-positive microglia are found throughout the nigrostriatal tract in PD brains (Hamza et al., Nature Genetics, 2010).
- LRRK2: Highly expressed in monocytes, microglia, and lymphocytes. Expression is upregulated in PD immune cells. LRRK2 modulates Toll-like receptor signaling and is also a susceptibility locus for Crohn’s disease and leprosy, reinforcing the immune connection (Gardet et al., PLOS ONE, 2010).
- PINK1/Parkin: Loss of Parkin leads to mitochondrial DNA leakage and activation of the cGAS-STING innate immune pathway, triggering neuroinflammation (Sliter et al., Nature, 2018).
9. Recent Discoveries (2024-2025)
| Gene | Year | Key Finding |
|---|---|---|
| RAB32 | 2024 | Ser71Arg variant identified as autosomal dominant PD cause; directly phosphorylated by LRRK2, unifying major PD pathways (Kholaparthy et al., The Lancet Neurology, 2024) |
| PSAP (PARK24) | 2024 | Prosaposin; precursor of saposins that activate lysosomal hydrolases including GCase; functionally connected to GBA1 pathway |
| PSMF1 | 2024 | Linked to early-onset PD with mitochondrial dysfunction (European Academy of Neurology, 2024) |
| SHLP2 | 2024 | Protective variant in mitochondrial microprotein reduces PD risk by ~50% (Yen et al., Molecular Psychiatry, 2024) |
| GUCY2C | 2024 | Loss of GUCY2C leads to mitochondrial dysfunction and dopamine neuron loss; potential therapeutic target |
10. Complete PARK Loci Reference Table
| PARK | Gene | Chromosome | Inheritance | Status |
|---|---|---|---|---|
| PARK1 | SNCA (missense) | 4q22.1 | AD | Confirmed |
| PARK2 | PRKN (Parkin) | 6q25.2-q27 | AR | Confirmed |
| PARK3 | Unknown | 2p13 | AD | Gene unidentified |
| PARK4 | SNCA (multiplications) | 4q22.1 | AD | Confirmed (=PARK1) |
| PARK5 | UCHL1 | 4p13 | AD | Single family; not replicated |
| PARK6 | PINK1 | 1p36.12 | AR | Confirmed |
| PARK7 | DJ-1 | 1p36.23 | AR | Confirmed |
| PARK8 | LRRK2 | 12q12 | AD | Confirmed |
| PARK9 | ATP13A2 | 1p36.13 | AR | Confirmed (Kufor-Rakeb) |
| PARK10 | USP24 (putative) | 1p32 | Susceptibility | Gene uncertain |
| PARK11 | GIGYF2 | 2q37.1 | AD | Not replicated |
| PARK12 | Unknown | Xq21-q25 | X-linked | Gene unidentified |
| PARK13 | HTRA2 | 2p13.1 | Uncertain | Uncertain |
| PARK14 | PLA2G6 | 22q13.1 | AR | Confirmed (atypical) |
| PARK15 | FBXO7 | 22q12.3 | AR | Confirmed (atypical) |
| PARK16 | RAB7L1/SLC41A1 | 1q32 | Susceptibility | GWAS risk locus |
| PARK17 | VPS35 | 16q11.2 | AD | Confirmed |
| PARK18 | EIF4G1 | 3q27.1 | AD | Not replicated |
| PARK19 | DNAJC6 | 1p31.3 | AR | Confirmed (atypical) |
| PARK20 | SYNJ1 | 21q22.11 | AR | Confirmed (atypical) |
| PARK21 | DNAJC13 | 3q22.1 | AD | Limited replication |
| PARK22 | CHCHD2 | 7p11.2 | AD | Emerging (East Asian) |
| PARK23 | VPS13C | 15q22.2 | AR | Stronger evidence |
| PARK24 | PSAP | 10q22.1 | AR | Recently identified |
11. Converging Cellular Pathways
The genes implicated in PD converge on eight major cellular pathways, suggesting that PD is not a single disease but a syndrome arising from dysfunction in interconnected biological processes:
| Pathway | Key Genes |
|---|---|
| 1. Alpha-synuclein proteostasis | SNCA, GBA1, LRRK2, VPS35, ATP13A2 |
| 2. Mitochondrial quality control / Mitophagy | PINK1, PRKN, DJ-1, VPS35, FBXO7, CHCHD2, VPS13C |
| 3. Lysosomal function | GBA1, ATP13A2, TMEM175, SCARB2, SMPD1, PSAP |
| 4. Endosomal / vesicle trafficking | VPS35, LRRK2, RAB7L1, RAB32, RAB39B, DNAJC6, SYNJ1, GAK |
| 5. Ubiquitin-proteasome system | PRKN, UCHL1, FBXO7 |
| 6. Immune / inflammatory signaling | HLA-DRB5, LRRK2, BST1, NOD2 |
| 7. Lipid metabolism | PLA2G6, GBA1 |
| 8. Synaptic function | SNCA, SYNJ1, DNAJC6, SYT11, SV2C |
12. Genetic Testing for Parkinson’s Disease
12.1 Available Testing Methods
- Clinical gene panels: Multi-gene panels (e.g., Mayo Clinic PARDP panel, Invitae Hereditary PD Panel) test for established PD genes. The standard seven-gene panel used in PD GENEration covers: GBA1, LRRK2, PRKN, SNCA, PINK1, PARK7 (DJ-1), and VPS35.
- Whole genome sequencing (WGS): PD GENEration transitioned to WGS in 2024, enabling detection of variants beyond the primary seven-gene panel.
- Direct-to-consumer testing: 23andMe tests only two variants (in LRRK2 and GBA1), which is extremely limited. A negative DTC result does not rule out genetic PD.
12.2 Who Should Be Tested
- Early-onset PD (before age 50)
- Family history (two or more first-degree relatives with PD)
- High-risk ancestry (Ashkenazi Jewish, North African Berber, Spanish Basque)
- Clinical trial eligibility (particularly for GBA1 and LRRK2 targeted trials)
- Universal testing is increasingly advocated: PD GENEration found that 9% of people with no high-risk factors still carry a reportable variant (Alcalay et al., Brain, 2024)
12.3 The PD GENEration Study
PD GENEration, powered by the Parkinson’s Foundation, is the largest global initiative offering free genetic testing and counseling for people with PD. Key milestones as of 2025:
- Over 22,000 participants tested
- 12.2-13% had a reportable genetic variant (substantially higher than earlier estimates of 5-10%)
- Transitioned to whole genome sequencing (WGS) in 2024
- Began returning secondary health findings (November 2024)
- Expanded internationally to Latin America, Israel, Canada
- Partnership with Morehouse School of Medicine for Black and African American inclusion
13. Gene Therapy Approaches
| Approach | Target | Status (2025) | Mechanism |
|---|---|---|---|
| AADC Gene Therapy | AAV2-AADC to putamen | Phase 3 (exPDite-2; NCT06944522) | Restores dopamine synthesis from L-DOPA; applicable to all PD regardless of genotype |
| GBA1 Gene Therapy | AAV9-GBA1 via intracisternal infusion | Phase 1/2 (NCT04127578) | Corrects glucocerebrosidase deficiency in GBA1-PD |
| LRRK2 Kinase Inhibitors | BIIB122 (small molecule) | Phase 2b (LUMA trial) | Reduces pathological LRRK2 kinase activity |
| LRRK2 ASO | BIIB094 (intrathecal) | Phase 1 (NCT03976349) | Reduces LRRK2 protein levels independent of specific mutations |
| SNCA ASO | Alpha-synuclein mRNA reduction | Phase 1 (NCT04165486) | Reduces alpha-synuclein expression |
| SNCA CRISPR | CRISPR-dCas9 methylation | Preclinical | Targeted epigenetic silencing of SNCA |
| GAD Gene Therapy | AAV-GAD to STN | Phase 1/2 (MeiraGTx) | Increases GABA to reduce STN overactivity |
14. Precision Medicine and Personalized Treatment
PD is increasingly recognized as a syndrome encompassing multiple pathophysiological subtypes rather than a single disease entity. Genetic characterization provides a molecular basis for personalized treatment strategies:
| Genetic Subtype | Targeted Approach |
|---|---|
| GBA1-PD | GCase activators (ambroxol), substrate reduction therapy, AAV9-GBA1 gene therapy |
| LRRK2-PD | LRRK2 kinase inhibitors, antisense oligonucleotides, PROTAC degraders |
| SNCA-PD | Alpha-synuclein ASOs, zinc finger repressors, CRISPR methylation, immunotherapy |
| PINK1/PRKN-PD | Mitochondrial enhancers, PINK1 activators, kinetin |
| All PD | AADC gene therapy, GAD gene therapy (symptomatic) |
Current challenges: Most PD remains genetically unexplained (only 5-10% monogenic; GWAS loci explain a fraction of heritability). Incomplete penetrance complicates risk prediction. Gene-environment interactions are poorly understood. Genomic diversity is lacking — most GWAS are European-centric (Blauwendraat et al., The Lancet Neurology, 2020).
15. Genetic Counseling for Parkinson’s Disease
Pre-test counseling should address: goals of testing, possible outcomes (positive, negative, variant of uncertain significance), implications for family members, emotional and psychological impact, and limitations of current knowledge. Post-test counseling should cover: result interpretation, discussion of penetrance and risk, family planning implications, clinical trial eligibility, and psychological support (Roberts et al., Genetics in Medicine, 2021).
Gene-specific considerations:
- GBA1 carriers: Counseling about Gaucher disease carrier status, variable penetrance (most carriers will not develop PD), and implications for offspring.
- LRRK2 G2019S carriers: Penetrance 25-42.5% by age 80; risk modified by polygenic background; clinical trial eligibility.
- Recessive genes (PRKN/PINK1/DJ-1): 25% recurrence risk for siblings of affected individuals; heterozygous carrier status for parents.
- Pre-symptomatic/at-risk relatives: Should be approached with caution due to psychological burden and current lack of preventive treatments.
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