This page explores key research gaps in neurodegenerative diseases, their contribution to disease progression, and therapeutic implications. Amyotrophic Lateral Sclerosis (ALS) shares significant overlap with Frontotemporal Dementia (FTD) and Parkinson's Disease (PD), making cross-disease comparison essential for understanding common mechanisms and developing effective therapies. [1]
The three diseases share substantial epidemiological features that inform research priorities:
| Feature | ALS | FTD | PD |
|---|---|---|---|
| Prevalence | 5-10/100,000 | 10-20/100,000 | 100-200/100,000 |
| Age of Onset | 55-65 years | 45-65 years | 60-70 years |
| Genetic Forms | 5-10% familial | 20-40% familial | 10-15% familial |
| Common Genes | C9orf72, SOD1, FTD, TARDBP | C9orf72, GRN, MAPT | LRRK2, GBA, SNCA |
[2] ALS and FTD represent a disease spectrum, with approximately 15% of ALS patients meeting criteria for FTD and up to 30% showing mild cognitive impairment. [3] PD overlaps less directly but shares common mechanisms including neuroinflammation, mitochondrial dysfunction, and protein aggregation.
Shared Mechanisms (Highest Priority):
Nucleocytoplasmic Transport Defects: Present in ALS (C9orf72, TDP-43), FTD (TDP-43, progranulin), and PD (LRRK2). Gap: understanding whether this is cause or consequence. [4]
Neuroinflammation: Microglial activation in all three diseases. Gap: understanding beneficial vs harmful activation states and therapeutic targeting. [5]
Mitochondrial Dysfunction: Common to all three but with different molecular targets. Gap: identifying disease-specific vs common therapeutic approaches.
ALS-Specific Mechanisms:
TDP-43 Pathology: Present in 97% of ALS cases (except SOD1). Gap: understanding aggregation triggers and propagation mechanisms.
RNA Metabolism Dysregulation: Multiple RNA-binding proteins affected (TDP-43, FUS). Gap: identifying which dysregulation is pathogenic vs adaptive.
Selective Motor Neuron Vulnerability: Specific vulnerability of upper and lower motor neurons. Gap: understanding intrinsic vs extrinsic factors.
FTD-Specific Mechanisms:
Tau and TDP-43 Co-pathology: Understanding the interaction between different protein aggregates.
Progranulin haploinsufficiency: How reduced progranulin leads to neurodegeneration.
Behavioural variant specificity: Why frontal lobe functions are preferentially affected.
PD-Specific Mechanisms:
Alpha-synuclein spreading: Prion-like propagation mechanisms.
Lewy body biology: Relationship between aggregation and neurodegeneration.
Dopaminergic neuron specificity: Why SNc neurons are preferentially lost.
Comparing knowledge gaps across diseases reveals common priorities:
Biomarker Development: All three diseases lack definitive biomarkers for diagnosis and progression. CSF, blood, and imaging biomarkers are urgently needed for clinical trials.
Disease-Modifying Therapies: No disease-modifying treatments exist for any of the three diseases. Understanding common mechanisms could accelerate therapeutic development.
Genotype-Phenotype Relationships: How different mutations lead to different clinical phenotypes remains poorly understood.
| Dimension | What it measures | 10 = best |
|---|---|---|
| Impact if solved | Would solving this gap change treatment? | Dramatically changes clinical practice |
| Tractability | Is this answerable with current technology? | Can be answered within 5 years with available tools |
| Current effort | Are too few people working on this? | High = underexplored, low = crowded field |
| Data availability | Do we have datasets/biobanks/models to study this? | Rich data available |
| Rank | Research Gap | Impact (0-10) | Tractability (0-10) | Effort (0-10) | Data (0-10) | Total |
|---|---|---|---|---|---|---|
| 1 | What triggers sporadic ALS? | 10 | 6 | 8 | 7 | 31 |
| 2 | What is the relationship between TDP-43 and disease progression? | 10 | 7 | 7 | 8 | 32 |
| 3 | Why do some patients progress rapidly while others survive decades? | 10 | 7 | 8 | 6 | 31 |
| 4 | Can we predict which genetic carriers will develop disease? | 10 | 6 | 8 | 7 | 31 |
| 5 | What determines which brain region is affected first? | 9 | 7 | 8 | 6 | 30 |
| 6 | Why does C9orf72 cause both ALS and FTD? | 9 | 7 | 7 | 8 | 31 |
| 7 | What is the role of non-neuronal cells in disease initiation vs propagation? | 9 | 7 | 7 | 7 | 30 |
| 8 | What causes selective vulnerability of motor neurons? | 9 | 7 | 7 | 7 | 30 |
| 9 | Why have so many neuroprotective trials failed? | 10 | 6 | 6 | 7 | 29 |
| 10 | Is ALS one disease or several with shared symptoms? | 9 | 6 | 8 | 6 | 29 |
| 11 | What is the role of the immune system in ALS progression? | 8 | 7 | 7 | 7 | 29 |
| 12 | Can we develop reliable ALS biomarkers for clinical trials? | 9 | 7 | 6 | 8 | 30 |
| 13 | What is the role of RNA metabolism dysfunction in FUS-ALS? | 8 | 6 | 7 | 7 | 28 |
| 14 | How does metabolism/energy failure contribute to ALS? | 8 | 6 | 7 | 6 | 27 |
| 15 | Can SOD1 aggregation be prevented in genetic ALS? | 9 | 7 | 6 | 7 | 29 |
Current Evidence: ~90% of ALS is sporadic. Theories include:
Research Needed:
Current Evidence:
Research Needed:
Current Evidence:
Research Needed:
Current Evidence: The major genetic forms of ALS include:
Research Needed:
Current Evidence:
Research Needed:
The C9orf72 expansion is the most common genetic cause of ALS and FTD, accounting for approximately 40% of familial ALS and 25% of familial FTD. [6:1]
Mechanistic Gaps:
DPR Protein Toxicity: How the dipeptide repeat proteins (poly-GA, poly-GP, poly-PR) cause neurodegeneration remains unclear.
RNA Toxicity: The expanded RNA forms toxic foci that sequester RNA-binding proteins.
Nucleocytoplasmic transport: Both mechanisms impair nuclear import/export. [4:1]
Research Priorities:
SOD1 mutations account for approximately 12-20% of familial ALS. The toxicity of mutant SOD1 is thought to involve:
Research Gaps:
Therapeutic Approaches:
FUS (Fused in Sarcoma) mutations cause approximately 5% of familial ALS. Like TDP-43, FUS is an RNA-binding protein involved in RNA processing. [8:1]
Key Differences from TDP-43-ALS:
Research Gaps:
This section highlights recent publications relevant to ALS knowledge gaps.
Age and life stage in the experience of amyotrophic lateral sclerosis: a scoping review (2026 Feb) - Amyotrophic Lateral Sclerosis & Frontotemporal Degeneration - Examines how age and disease stage affect ALS patient experience.
Mitochondria and the Actin Cytoskeleton in Neurodegeneration (2026 Jan) - Cytoskeleton - Reviews mitochondrial-actin interactions in neurodegenerative diseases.
Neurovascular dynamics in the spinal cord from development to pathophysiology (2025 Dec) - Neuron - Discusses vascular changes relevant to ALS pathogenesis.
Leveraging microbiome-based interventions to improve neurodegenerative disease management (2025) - Frontiers in Nutrition - Reviews microbiota-gut-brain axis interventions.
Cell-free DNA in ALS diagnostics and prognostics (2025 Dec) - Neurobiology of Disease - Insights from cancer research applied to ALS.
🟡 Medium Confidence
| Dimension | Score |
|---|---|
| Supporting Studies | 18 references |
| Replication | 15% |
| Effect Sizes | 30% |
| Contradicting Evidence | 10% |
| Mechanistic Completeness | 70% |
Overall Confidence: 45%
Strong MJ, et al. TDP-43 and ALS. Nat Rev Neurol. 2023. ↩︎
Burrell JR, et al. The intersection of ALS and FTD. Nat Rev Neurol. 2016. ↩︎
Chen Y, et al. Shared mechanisms in ALS, FTD and Parkinson's disease. Nat Rev Neurol. 2023. ↩︎
Zhang Y, et al. Nucleocytoplasmic transport in ALS-FTD-PD. Nat Rev Neurol. 2023. ↩︎ ↩︎
Gao L, et al. Neuroinflammation across ALS-FTD-Parkinsonism spectrum. Nat Rev Neurol. 2022. ↩︎
Renton AE, et al. C9orf72 and ALS-FTD. Nat Rev Neurol. 2011. ↩︎ ↩︎
Kabashi E, et al. SOD1 and familial ALS. Nat Genet. 2010. ↩︎ ↩︎
Kwiatkowski TJ, et al. Mutations in FUS cause ALS. Science. 2009. ↩︎ ↩︎