Neurofilament-light chain (NFL) is a structural protein that provides stability and support to neuronal axons. It is a sensitive biomarker for axonal damage in neurodegenerative diseases, including Alzheimer's disease, Parkinson's disease, and ALS.
Neurofilaments are intermediate filaments (10nm diameter) that form the neuronal cytoskeleton. They consist of three subunits:
- Neurofilament-light (NFL): ~60 kDa
- Neurofilament-medium (NFM): ~95 kDa
- Neurofilament-heavy (NFH): ~200 kDa
NFL forms the core scaffold, with NFM and NFH associating as side-arm proteins.
NFL has a tripartite structure:
- Head domain: Non-alpha helical, involved in assembly
- Rod domain: Alpha-helical coiled-coil, ~310 amino acids
- Tail domain: Variable length, contains phosphorylation sites
The protein is encoded by the NEFL gene on chromosome 8p21.2.
- Axonal stability: Maintains axonal caliber and structural integrity
- Fast axonal transport: Associates with motor proteins for organelle transport
- Myelination regulation: Influences myelination through interactions with myelin-producing cells
- Synaptic function: Involved in synaptic vesicle trafficking
- Axonal damage marker: NFL levels in CSF correlate with disease severity
- Predictive biomarker: Elevated NFL predicts cognitive decline
- Tau correlation: NFL correlates with tau pathology burden
- Disease progression marker: Higher NFL in PD patients with cognitive impairment
- Dopaminergic neuron loss: Reflects degeneration of substantia nigra neurons
- DLB/PDD: Elevated in dementia with Lewy bodies
- Highly sensitive marker: NFL is one of the most promising biomarkers for ALS
- Disease progression: Rapidly increases with disease progression
- Prognostic value: Higher levels correlate with shorter survival
- Therapeutic trials: Used as outcome measure in clinical trials
- Multiple system atrophy (MSA): Elevated NFL in CSF
- Progressive supranuclear palsy (PSP): Marker of disease severity
- Frontotemporal dementia (FTD): Reflects neuronal loss
NFL is measured in:
- Cerebrospinal fluid (CSF): Gold standard
- Blood/plasma: Emerging as less invasive alternative
- Neuroimaging: Developmental as PET ligands
- Biomarker development: NFL-targeted assays for early diagnosis
- Clinical trials: Endpoint measure for drug efficacy
- Personalized medicine: Individual disease monitoring
- Neurofilament light chain as biomarker in ALS (Gaetz et al., 2023)
- NFL in Alzheimer's disease progression (Zetterberg, 2016)
- Blood neurofilament in Parkinson's disease (Lin et al., 2022)
- Nixon RA, et al. Neurofilament proteins in axonal transport. J Neurosci. 1994
- Lee MK, Cleveland DW. Neuronal intermediate filaments. Annu Rev Neurosci. 1996
- Petzold A. Neurofilament phosphoforms: surrogate markers for axonal injury. Ann Neurol. 2005
- Khalil M, et al. Neurofilaments as biomarkers in neurology. Nat Rev Neurol. 2020