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Medicine » "Update on Amyotrophic Lateral Sclerosis", book edited by Humberto Foyaca Sibat and Lourdes de Fatima Ibañez Valdés, ISBN 978-953-51-2601-0, Print ISBN 978-953-51-2600-3, Published: September 14, 2016 under CC BY 3.0 license. © The Author(s).

Chapter 10

Neuronal Intermediate Filaments in Amyotrophic Lateral Sclerosis

By Philippe Codron, Julien Cassereau, Joël Eyer and Franck Letournel
DOI: 10.5772/63161

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Schematic representation of adult neuronal IF subunits. All NIF subunits share a highly conserved central helical domain of 310 amino acid residues involved in the formation of coiled‐coil structures. Flanking this central rod domain are the amino‐ and the carboxy‐terminal domains conferring functional specificity to the different types of NIF proteins. The NFM and NFH carboxy‐terminal regions contain Lys‐Ser‐Pro (KSP) repeats, which can be phosphorylated. Abbreviations: NF, neurofilament; NFL, NF‐light; NFM, NF‐medium; NFH, NF‐heavy; C, carboxy‐terminal; N, amino‐terminal.
Figure 1. Schematic representation of adult neuronal IF subunits. All NIF subunits share a highly conserved central helical domain of 310 amino acid residues involved in the formation of coiled‐coil structures. Flanking this central rod domain are the amino‐ and the carboxy‐terminal domains conferring functional specificity to the different types of NIF proteins. The NFM and NFH carboxy‐terminal regions contain Lys‐Ser‐Pro (KSP) repeats, which can be phosphorylated. Abbreviations: NF, neurofilament; NFL, NF‐light; NFM, NF‐medium; NFH, NF‐heavy; C, carboxy‐terminal; N, amino‐terminal.
Schematic model of IF assembly in mature neurons. Two NIF subunits (NFL and either NFH or NFM) form head‐to‐tail coiled‐coil dimers (a), anti‐parallel half‐staggered tetramers (b), protofilaments (c) and 10‐nm NF (d). C‐terminal domains of NFM and NFH form lateral projections and participate in the stabilisation of the filament network [33].
Figure 2. Schematic model of IF assembly in mature neurons. Two NIF subunits (NFL and either NFH or NFM) form head‐to‐tail coiled‐coil dimers (a), anti‐parallel half‐staggered tetramers (b), protofilaments (c) and 10‐nm NF (d). C‐terminal domains of NFM and NFH form lateral projections and participate in the stabilisation of the filament network [33].
Schematic representation of the cytoskeleton organisation in axons. The components of the axoplasm are organised into a three‐dimensional array interconnected by NFM and NFH tails and plakin‐family proteins [39].
Figure 3. Schematic representation of the cytoskeleton organisation in axons. The components of the axoplasm are organised into a three‐dimensional array interconnected by NFM and NFH tails and plakin‐family proteins [39].
Neuropathological features in ALS. Immunohistochemistry for neurofilaments subunit (phosphorylated form): diffuse labelling in neuronal swelling perikarya (a) and axonal spheroids (b) in ventral horn of cervical spine. Scale bars, 20 μm.
Figure 4. Neuropathological features in ALS. Immunohistochemistry for neurofilaments subunit (phosphorylated form): diffuse labelling in neuronal swelling perikarya (a) and axonal spheroids (b) in ventral horn of cervical spine. Scale bars, 20 μm.

Neuronal Intermediate Filaments in Amyotrophic Lateral Sclerosis

Philippe Codron1, 2, 3, Julien Cassereau2, 3, Joël Eyer4 and Franck Letournel1, 4
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Neuronal intermediate filaments (NIFs) are the most abundant cytoskeletal element in mature neurons. They are composed of different protein subunits encoded by separate genes such as neurofilament light chain (NFL), neurofilament medium chain (NFM), neurofilament heavy chain (NFH), ɑ‐internexin and peripherin. NIFs are dynamic structures playing important functions in cell architecture and differentiation, interactions between proteins or subcellular organelles, and in axonal calibre determination and myelination. Consequently, their presence modulates electrophysiological properties of axons. NIFs have long been assigned a role in the pathogenesis of amyotrophic lateral sclerosis (ALS). Indeed, accumulation and abnormal phosphorylation of NIF subunits in motor neuron are one of the major pathological features in both sporadic and familial forms of the disease. Moreover, mutations in the NFH and peripherin genes and elevated cerebrospinal fluid NIF levels reported in ALS cases, associated with studies in transgenic mice, provided the evidence that primary defects in NIFs could be causative for motor neuron disease. However, the processes leading to the NIF abnormalities and the links to the pathogenesis of ALS remain unclear, leaving a challenging open field for further investigations in this highly disabilitating disease. Here, we review the main characteristics of these NIFs and their involvement in the pathomechanisms of ALS.

Keywords: Intermediate filaments, Neurofilaments, cytoskeleton, amyotrophic lateral sclerosis, tubulin, microtubules, axonal transport

1. Neuronal intermediate filaments

1.1. Characteristics

Intermediate filaments (IFs) are components of the cytoskeleton, together with microtubules (MTs) and microfilaments. IFs are defined by their diameter when examined by transmission electronic microscopy (10 nm), which is intermediate between microtubules (15 nm) and microfilaments (6 nm). They also differ from these two structures by the various sizes and primary organisation of their constitutive proteins, their non‐polar architecture and their relative insolubility. Intermediate filaments form a large family of proteins; they are classified into five types according to their gene organisation, size, structure and cell‐type expression (Table 1). IFs expressed in neurons of the central and peripheral nervous systems are called neuronal intermediate filaments (NIFs) and include nestin, synemin, vimentin, α‐internexin, peripherin and neurofilaments (NFs) that are composed of three subunits, neurofilament light chain (NFL), neurofilament medium chain (NFM) and neurofilament heavy chain (NFH) (for low‐, medium‐, and high‐molecular‐weight NFs) [15].

Neurons express differentially IF proteins depending on their developing stage and their localisation in the nervous system. While nestin, synemin and vimentin are mainly expressed during the neuronal development, NFs, peripherin and ɑ‐internexin are the main intermediate filament subunits in mature neurons from the central and peripheral nervous system [6]. In this chapter, we focus on those three subtypes of NIFs.

IAcid keratinsEpithelia
IIBasic keratinsEpithelia
PeripherinPNS neurons
IVNeurofilaments (NFL, NFM, NFH)PNS and CNS neurons
ɑ‐InternexinCNS neurons
NestinCNS stem cells
VNuclear laminsNucleus

Table 1.

Classification of intermediate filaments.

[i] - IFs found in mature neurons are NFL, NFM, NFH, peripherin and α‐internexin. Abbreviations: GFAP, glial fibrillary acidic protein; CNS, central nervous system; PNS, peripheral nervous system [7].

1.2. Expression and post‐translational modifications

Genes coding for NFL and NFM (NEFL and NEFM) are closely linked on chromosome 8 (8p21), while NFH gene (NEFH) is located on chromosome 22 (22q12.2) [810]. Peripherin is encoded by PRPH located on chromosome 12 (q12–q13) [11], and ɑ‐internexin is encoded by INA located on chromosome 10 (10q24.33) [3]. As for other IFs, NFs, peripherin and ɑ‐internexin share a common tripartite structure, with non‐helical amino‐ and carboxy‐terminal regions (head and tail domains) flanking a 46‐nm‐long central α‐helical rod domain composed of approximately 310 highly conserved amino acids [9, 10, 12] (Figure 1). These segments are joined by short non‐helical linker sequences, aligning the individual IF subunits prior to filament assembly. While peripherin and NFL have a short‐tail domain, those of NFM and NFH are longer and contain numerous KSP (Lys‐Ser‐Pro) repeats that can be phosphorylated on serine (S) residues. These sites are frequently modified by phosphorylation, glycosylation, nitration, oxidation and ubiquitination, which can impact NIF interactions and dynamics [6].


Figure 1.

Schematic representation of adult neuronal IF subunits. All NIF subunits share a highly conserved central helical domain of 310 amino acid residues involved in the formation of coiled‐coil structures. Flanking this central rod domain are the amino‐ and the carboxy‐terminal domains conferring functional specificity to the different types of NIF proteins. The NFM and NFH carboxy‐terminal regions contain Lys‐Ser‐Pro (KSP) repeats, which can be phosphorylated. Abbreviations: NF, neurofilament; NFL, NF‐light; NFM, NF‐medium; NFH, NF‐heavy; C, carboxy‐terminal; N, amino‐terminal.

Multiple aspects of IF biology are regulated by their post‐translational modifications. The phosphorylation state of NIF proteins depends on a dynamic balance between the activities of kinases and phosphatases. Phosphorylation of the head domain by secondary‐messenger‐dependent protein kinase A (PKA) and protein kinase C (PKC) prevents NIF subunits assembly or leads to the disassembly of pre‐existing filaments [13, 14]. Phosphorylation of the KSP motifs on NFM and NFH tail domains by cyclin‐kinase Cdk5 and microtubule‐associated protein (MAP) kinase promotes the formation of cross‐bridges with MTs and slows NF axonal transport [15, 16]. Phosphorylation of the head and tail domains is closely related; indeed, phosphorylation of NFM head domain by PKA reduces the phosphorylation of tail domain by MAP kinases [17]. This mechanism could be a way to protect neurons from abnormal accumulation of phosphorylated NIFs in perikarya. NIF dephosphorylation is mainly catalysed by phosphatase 2A; dephosphorylation of the head domain is necessary to allow NIF polymerization and transport into the axon, while dephosphorylation of the tail domain facilitates their interaction with other cytoskeletal proteins and their degradation [18, 19].

NIFs are also post‐translationally modified by glycosylation and nitration. Glycosylation resides on attachment of O‐linked N‐acetyl glucosamine (O‐GlcNAc) to S and threonine (T) residues; the precise function of glycosylation is still unknown, but several clues suggest a role in the NIF assembly [20]. NIF nitration is catalysed by superoxide dismutase 1 (SOD1) on tyrosine residues; the nitration of NIFs changes hydrophobic residues into negatively charged hydrophilic residues, thereby disrupting their assembly and stability.

1.3. Transport, assembly and degradation

Following their synthesis in the cell body, NIF proteins are assembled into filamentous structures and transported into the axons. They are transported bidirectionally in the axon along microtubules using kinesin (anterograde) or dynein (retrograde) motor proteins [21, 22]. Studies analysing the transport of green‐fluorescent protein (GFP)‐tagged NIF subunits have shown that NIFs are transported intermittently in axons, their movements being interrupted by prolonged pauses. Only a small fraction of NIFs moves at any given time and direction, and approximately 97% of NIFs spent their time pausing [2325]. The direction of NIF transport is modulated by their phosphorylation status, since phosphorylation promotes their release from kinesin and increases their affinity for dynein [22, 26].


Figure 2.

Schematic model of IF assembly in mature neurons. Two NIF subunits (NFL and either NFH or NFM) form head‐to‐tail coiled‐coil dimers (a), anti‐parallel half‐staggered tetramers (b), protofilaments (c) and 10‐nm NF (d). C‐terminal domains of NFM and NFH form lateral projections and participate in the stabilisation of the filament network [33].

NIF subunits can assemble into filaments as soon as they are expressed in neurons, depending on their post‐translational modifications. Subunits can also disassemble and reassemble during their transport. NIF assembly does not require nucleotide binding or hydrolysis. The first step of the filament formation is the dimerisation of an NFL subunit with either an NFM or an NFH subunit, via the association of their rod domains to form parallel side‐to‐side coiled‐coil dimers. Two coiled‐coil dimers line up in a half‐staggered manner, forming an anti‐parallel tetramer. Tetramers combine to form protofilaments, which finally assemble to constitute the final 10‐nm filament [27, 28] (Figure 2). The C‐terminal domains of NFM and NFH form lateral projections extending from the filament core [29]. Those projections participate to the stabilisation of the filament network and interact with other filament structures and subcellular organelles. Peripherin and α‐internexin can co‐assemble with NFL, NFM and NFH to form NIFs in mature neurons, respectively, in the peripheral and in the central nervous system [3032]. Thus, NIFs are heteropolymers composed of different subunits, with a ratio changing during neuronal development and activity. This stoichiometry is particularly important and can lead to severe NF disorganisation when unbalanced.

In normal neurons, non‐phosphorylated NIFs are found primarily in the soma and proximal axons, while phosphorylated NIFs are located more distal in axons and in terminals [34]. Inside the axon, NIFs are organised into a three‐dimensional array interconnected with the other components of the cytoskeleton by several cross‐bridges. NIFs, microtubules and actin filaments are interlinked by proteins of the plakin family including, among others, plectin, bullous pemphigoid antigen‐1 protein (BPAG1), actin cross‐linking factor 7 (ACF7), desmoplakin, envoplakin and periplakin [3538]. Lateral projections of NFH and NFM tails also fasten adjacent structures (Figure 3).


Figure 3.

Schematic representation of the cytoskeleton organisation in axons. The components of the axoplasm are organised into a three‐dimensional array interconnected by NFM and NFH tails and plakin‐family proteins [39].

Following their synthesis, assembly and disassembly, NIFs are slowly transported towards the nerve terminal where they are degraded by specific calcium‐activated proteases, such as calpain I, and neutral proteases. NIFs are also degraded by non‐specific proteases like cathepsin D, trypsin and α‐chymotrypsin. As mentioned above, post‐translational modifications regulate NIF degradation: for example, phosphorylation protects NIFs from proteolysis, while ubiquitination facilitates their degradation [40, 41].

1.4. Roles

As members of the cytoskeletal system, NIFs work together with microtubules and microfilaments to enhance structural integrity and cell shape [42]. In the last decades, it has become increasingly apparent that IFs, instead of being inert, are in fact highly dynamic structures [43] relaying signals from the plasma membrane to the nucleus [44], orchestrating the position and function of cellular organelles [45] and regulating protein synthesis [46]. These interactions are principally mediated through NIF‐associated proteins that can modulate NIF structure and function. Linker proteins such as Fodrin, Hamartin or MAP2 are responsible for NIF interactions with filaments and organelles [29, 47, 48], whereas enzymes (principally kinases and phosphatases) modulate their architecture, assembly and spacing.

Another major role recognised for NIFs is to modulate the calibre of axons, with a direct repercussion on the axonal conduction velocity, myelin thickness and inter‐nodal length. Indeed, NIF density is correlated with axonal calibre in sciatic nerve fibres of rats and mice [49]. Moreover, the axonal radial growth during axonal development or regeneration coincides with the entry of NFs into axons [50]. In the same way, triple heterozygous knockout mice (NFL±, NFM± and NFH±), with a reduction of NF content but with a normal structure and stoichiometry of the NIF network, exhibit a 50% decrease of the axonal diameter in L5 ventral root [51]. Finally, the disruption of the NFM gene expression or the deletion of its carboxy‐terminal domain in mice reduces the inter‐filament spacing and axonal calibre, illustrating the preponderant role of NFM in determining axonal diameter [52, 53]. The phosphorylation state of NFM and NFH carboxy‐terminal domains might be linked to axon calibre control by regulating NF transport and inter‐filament spacing, but the exact mechanisms remain unknown.

Thus, NIFs have a central role in cell architecture, dynamics of the organelles, axon structure and calibre. Therefore, defects in their metabolism could lead to neurodegenerative processes.

2. Implication in amyotrophic lateral sclerosis

2.1. Clinical features

Amyotrophic lateral sclerosis (ALS) is a progressive neurodegenerative disease characterised by the loss of motor neurons of the spinal cord, brain stem and motor cortex. Common clinical symptoms of the disease are progressive paralysis, muscle atrophy and death within 2–5 years usually from respiratory failure [54]. Although most cases are sporadic (sALS), approximately 10% of ALS patients have a positive family history (fALS). To date, there is no curative treatment of the disease.

Primary evidence for a contribution of NIFs in ALS pathogenesis came from neuropathological observations. Most of all, ALS is characterised by the loss and degeneration of upper motor neurons in the motor cortex (Betz cells), and lower motor neurons in the brainstem (cranial motor nuclei) and spinal cord (anterior horn) [55]. One of the hallmarks of both sporadic and familial ALS is the presence of inclusion bodies in the perikarya of degenerating motor neurons, described as Lewy body‐like inclusions (LBLIs), Skein‐like inclusions (SLIs) or hyaline conglomerate inclusions (HCIs). Other typical images observed in the disease are motor neurons with swollen argyrophilic perikarya, and large swellings of the proximal part of the axons called spheroids. In immunocytochemical studies, these abnormalities have been shown to contain several proteins, such as ubiquitin or stable tubule‐only polypeptide (STOP) [56], but they are particularly reactive for neurofilament subunits [57, 58] and peripherin [59, 60] (Figure 4). Interestingly, NIF inclusions in the cell body and the proximal axon are hyperphosphorylated, while as mentioned above in normal neurons NIFs are dephosphorylated in those sites and only phosphorylated in more distal part of the axon.


Figure 4.

Neuropathological features in ALS. Immunohistochemistry for neurofilaments subunit (phosphorylated form): diffuse labelling in neuronal swelling perikarya (a) and axonal spheroids (b) in ventral horn of cervical spine. Scale bars, 20 μm.

Evidence for the involvement of NIFs in the pathogenesis of ALS has been reinforced in the last 20 years by the discovery of NIF gene mutations linked to the disease. Indeed, codon deletions and insertions in PRPH and NEFH genes have been identified in several sporadic ALS patients [6164]. Although these mutations are not considered as a cause of familial ALS, they could be a risk factor for sporadic ALS occurrence.

Other evidences came from several studies showing that cerebrospinal fluid NIF levels are significantly higher in ALS patients than in patients with other neurodegenerative diseases, especially for those with rapidly progressive disease [65, 66]. Although their contributions to ALS pathogenesis remain unclear, all these clinical and neuropathological features suggest that NIFs represent a component of the pathological mechanisms of the disease.

2.2. Animal model contributions

On the basis of these findings, several animal models have been developed, including mice knockout for NIF genes, and mice expressing mouse, human and modified NIF subunits. While deletions of NIF genes have limited phenotype and thus are not extensively used to study ALS pathogenesis, the axonal calibre reduction seen in knockout mice for NFL, NFM and NFH genes demonstrated that neurofilaments play an important role in the radial growth of axons (Table 2). Interestingly, transgenic mice overexpressing either NFL, NFM, NFH, human NFH, peripherin or a mutated NFL show clinical and/or neuropathological alterations similar to those found in ALS (Table 3). Finally, in order to investigate NF dynamics, NFH‐LacZ and NFH‐GFP mice have been generated; while NFs are retained in cell bodies and deficient in axons in NFH‐LacZ mice, the fluorescent fusion protein is normally transported along axons in NFH‐GFP mice, suggesting that β‐galactosidase reporter alters the fusion protein dynamics whereas GFP does not [67, 68]. All these animal models are therefore very useful to study the processes underlying NIF accumulation and their role in motor neuron death.

MiceMotor dysfunctionAxonal calibre reductionReferences
NFL -/-No>50%[69]
NFM -/-No>50%[70]
NFH -/-No10%[71]
α‐Internexin -/-NoNo[72]
Peripherin -/-NoNo[73]

Table 2.

Knockout mice for NIF genes.

MiceMotor dysfunctionNF inclusionsReferences
Mouse NFLYesSpinal motor neurons and DRG[74]
Mouse NFMNoSpinal motor neurons and DRG[75]
Mouse NFHNoSpinal motor neurons and DRG[76]
Human NFLNoThalamus and cortex[77]
Human NFMNoCortex and forebrain[78]
Human NFHYesSpinal motor neurons and DRG[79]
Mutated NFL (tail)YesSpinal motor neurons and DRG[80]
α‐InternexinNoPurkinje cells[81]
PeripherinYesSpinal motor neurons[82]

Table 3.

Mice overexpressing neuronal IF genes or expressing mutated neuronal IF proteins.

2.3. Pathophysiological hypotheses

Accumulation of neurofilaments in motor neurons undeniably participates in the pathogenesis of ALS, breaking perikarya and axonal structures, disrupting organelles dynamics and interactions, and affecting axonal transport. However, it is still difficult to determine whether NIF aggregations are the cause or consequence of the disease. For example, the motor neuron loss caused by SOD1G85R mutation is still present despite the absence of NFL in transgenic mice [83, 84], but the animal's lifespan is prolonged by approximately 15%, suggesting an increased neuron toxicity when NFs are present in SOD1‐mediated disease.

The mechanisms governing the formation of IF aggregates in ALS remain unclear because multiple factors can potentially induce the accumulation of NIFs. Firstly, these accumulations could result from perturbations of NIF transport through their abnormal phosphorylation, leading to accumulation in cell bodies and in proximal axons. Glutamate excitotoxicity could be involved in this process by activating mitogen‐activated protein kinases and protein kinase N1 [85, 86]. Direct disruption of the transport motors themselves could also result in NIF accumulation, as it has been demonstrated in transgenic mice harbouring mutations or modified expression in kinesin and dynein genes [87]. Finally, one of the emerging hypotheses is that the aggregation of NIFs in ALS could result from their altered stoichiometry. Indeed, overexpression of NFL, NFM or NFH in mice provokes NF aggregations and morphological alterations similar to those found in ALS [7476]. Remarkably, the motor neuron disease caused by excess of human NFH in transgenic mice can be rescued by a correct stoichiometry with the co‐expression of human NFL transgene in a dosage‐dependent fashion [88]. In a similar way, the onset of peripherin‐mediated disease in transgenic mice overexpressing PRPH is accelerated by the deficiency of NEFL [82], peripherin interacting with NFM and NFH to form disorganised NIF structures. Another interesting point supporting this hypothesis is that NFL mRNA level is 70% decreased in degenerating motor neurons from ALS patients [89]. This could be due to reduced transcript stability, with a possible involvement of mutated SOD1 and TAR DNA‐binding protein (TDP‐43) that can bind and destabilise NFL mRNA [90, 91].

2.4. The paradox concerning perikaryal versus axonal aggregation of NIF, and the protective effect of perycarial NFH accumulation

Transgenic mice carrying mutant SOD1 transgenes develop neuronal, clinical and pathological features similar to those observed in ALS [92]. Surprisingly, the removal of axonal NIF by crossing the SOD1 transgenic mice with the NFH‐LacZ transgenic mice does not affect the pathogenesis induced by SOD1 suggesting that axonal neurofilament aggregation is not the cause of ALS [93]. On the other side, overexpression of mouse NFL and NFH in SOD1G93A mice and overexpression of human NFH in SOD1G37R mice increase their lifespan by, respectively, 15 and 65%, associated with an increase of perycarial NF inclusions and a decrease of axonal spheroids (Table 4). Taken together, these last results suggest a protective effect of perikaryal accumulation of NFH proteins in motor neuron disease caused by mutant SOD1. Several hypotheses have been proposed to explain this protective effect. One possibility is that NF proteins may act as calcium chelators thanks to their multiple calcium‐binding sites [94]. It also cannot be excluded that the accumulation of NFs could interfere with glutamate receptors and prevent glutamate excitotoxicity [95]. Finally, NF inclusions may act as a phosphorylation sink for cyclin‐dependent kinase 5 or for toxic oxygen radical species induced by mutant SOD1, thereby reducing damage to other essential cellular components [96].

MiceLifespanPerycarial NF inclusionsReferences
SODG85R – NFL -/-Increased by 15%No change[84]
SODG93A – NFL overexpressionIncreased by 15%Increased[97]
SODG93A – NFH overexpressionIncreased by 15%Increased[97]
SODG37R – human NFH overexpressionIncreased by 65%Increased[98]

Table 4.

Effects of NF changes in SOD1‐mediated disease.

3. Future directions

Implications of NIF abnormalities in the pathogenesis of ALS remain unclear. Despite extensive studies over the past 20 years, it is still unknown how these abnormalities occur and what are their exact contributions to the disease pathogenesis. Understanding how they are formed remains an important objective in the study of both sporadic and familial forms of the disease. Perhaps, the analysis of future generation of mouse models with new familial ALS mutations or conditional control of abnormal NIF proteins will help to address this issue.


1 - Izmiryan A, Cheraud Y, Khanamiryan L, Leterrier JF, Federici T, Peltekian E, et al. Different expression of synemin isoforms in glia and neurons during nervous system development. Glia. 2006 Aug 15;54(3):204–13.
2 - Julien JP, Mushynski WE. Neurofilaments in health and disease. Prog Nucleic Acid Res Mol Biol. 1998;61:1–23.
3 - Kaplan MP, Chin SS, Fliegner KH, Liem RK. Alpha‐internexin, a novel neuronal intermediate filament protein, precedes the low molecular weight neurofilament protein (NF‐L) in the developing rat brain. J Neurosci. 1990 Aug;10(8):2735–48.
4 - Lendahl U, Zimmerman LB, McKay RD. CNS stem cells express a new class of intermediate filament protein. Cell. 1990 Feb 23;60(4):585–95.
5 - Portier MM, de Néchaud B, Gros F. Peripherin, a new member of the intermediate filament protein family. Dev Neurosci. 1983–1984;6(6):335–44.
6 - Perrot R, Berges R, Bocquet A, Eyer J. Review of the multiple aspects of neurofilament functions, and their possible contribution to neurodegeneration. Mol Neurobiol. 2008 Aug;38(1):27–65.
7 - Liu Q, Xie F, Siedlak SL, Nunomura A, Honda K, Moreira PI, et al. Neurofilament proteins in neurodegenerative diseases. Cell Mol Life Sci. 2004 Dec;61(24):3057–75.
8 - Hurst J, Flavell D, Julien JP, Meijer D, Mushynski W, Grosveld F. The human neurofilament gene (NEFL) is located on the short arm of chromosome 8. Cytogenet Cell Genet. 1987;45(1):30–2.
9 - Lees JF, Shneidman PS, Skuntz SF, Carden MJ, Lazzarini RA. The structure and organization of the human heavy neurofilament subunit (NF‐H) and the gene encoding it. EMBO J. 1988 Jul;7(7):1947–55.
10 - Myers MW, Lazzarini RA, Lee VM, Schlaepfer WW, Nelson DL. The human mid‐size neurofilament subunit: a repeated protein sequence and the relationship of its gene to the intermediate filament gene family. EMBO J. 1987 Jun;6(6):1617–26.
11 - Moncla A, Landon F, Mattei MG, Portier MM. Chromosomal localisation of the mouse and human peripherin genes. Genet Res. 1992 Apr;59(2):125–9.
12 - Foley J, Ley CA, Parysek LM. The structure of the human peripherin gene (PRPH) and identification of potential regulatory elements. Genomics. 1994 Jul 15;22(2):456–61.
13 - Hisanaga S, Gonda Y, Inagaki M, Ikai A, Hirokawa N. Effects of phosphorylation of the neurofilament L protein on filamentous structures. Cell Regul. 1990 Jan;1(2):237–48.
14 - Sihag RK, Jaffe H, Nixon RA, Rong X. Serine‐23 is a major protein kinase A phosphorylation site on the amino‐terminal head domain of the middle molecular mass subunit of neurofilament proteins. J Neurochem. 1999 Feb;72(2):491–9.
15 - Ackerley S, Thornhill P, Grierson AJ, Brownlees J, Anderton BH, Leigh PN, et al. Neurofilament heavy chain side arm phosphorylation regulates axonal transport of neurofilaments. J Cell Biol. 2003 May 12;161(3):489–95.
16 - Nixon RA, Brown BA, Marotta CA. Posttranslational modification of a neurofilament protein during axoplasmic transport: implications for regional specialization of CNS axons. J Cell Biol. 1982 Jul;94(1):150–8.
17 - Zheng Y‐L, Li B‐S, Veeranna null, Pant HC. Phosphorylation of the head domain of neurofilament protein (NF‐M): a factor regulating topographic phosphorylation of NF‐M tail domain KSP sites in neurons. J Biol Chem. 2003 Jun 27;278(26):24,026–32.
18 - Saito T, Shima H, Osawa Y, Nagao M, Hemmings BA, Kishimoto T, et al. Neurofilament‐associated protein phosphatase 2A: its possible role in preserving neurofilaments in filamentous states. Biochemistry. 1995 Jun 6;34(22):7376–84.
19 - Veeranna null, Shetty KT, Link WT, Jaffe H, Wang J, Pant HC. Neuronal cyclin‐dependent kinase‐5 phosphorylation sites in neurofilament protein (NF‐H) are dephosphorylated by protein phosphatase 2A. J Neurochem. 1995 Jun;64(6):2681–90.
20 - Dong DL, Xu ZS, Chevrier MR, Cotter RJ, Cleveland DW, Hart GW. Glycosylation of mammalian neurofilaments. Localization of multiple O‐linked N‐acetylglucosamine moieties on neurofilament polypeptides L and M. J Biol Chem. 1993 Aug 5;268(22):16,679–87.
21 - Shah JV, Flanagan LA, Janmey PA, Leterrier JF. Bidirectional translocation of neurofilaments along microtubules mediated in part by dynein/dynactin. Mol Biol Cell. 2000 Oct;11(10):3495–508.
22 - Yabe JT, Pimenta A, Shea TB. Kinesin‐mediated transport of neurofilament protein oligomers in growing axons. J Cell Sci. 1999 Nov;112(Pt 21):3799–814.
23 - Roy S, Coffee P, Smith G, Liem RK, Brady ST, Black MM. Neurofilaments are transported rapidly but intermittently in axons: implications for slow axonal transport. J Neurosci. 2000 Sep 15;20(18):6849–61.
24 - Trivedi N, Jung P, Brown A. Neurofilaments switch between distinct mobile and stationary states during their transport along axons. J Neurosci. 2007 Jan 17;27(3):507–16.
25 - Wang L, Ho CL, Sun D, Liem RK, Brown A. Rapid movement of axonal neurofilaments interrupted by prolonged pauses. Nat Cell Biol. 2000 Mar;2(3):137–41.
26 - Motil J, Chan WK‐H, Dubey M, Chaudhury P, Pimenta A, Chylinski TM, et al. Dynein mediates retrograde neurofilament transport within axons and anterograde delivery of NFs from perikarya into axons: regulation by multiple phosphorylation events. Cell Motil Cytoskeleton. 2006 May;63(5):266–86.
27 - Angelides KJ, Smith KE, Takeda M. Assembly and exchange of intermediate filament proteins of neurons: neurofilaments are dynamic structures. J Cell Biol. 1989 Apr;108(4):1495–506.
28 - Heins S, Wong PC, Müller S, Goldie K, Cleveland DW, Aebi U. The rod domain of NF‐L determines neurofilament architecture, whereas the end domains specify filament assembly and network formation. J Cell Biol. 1993 Dec;123(6 Pt 1):1517–33.
29 - Hirokawa N, Glicksman MA, Willard MB. Organization of mammalian neurofilament polypeptides within the neuronal cytoskeleton. J Cell Biol. 1984 Apr;98(4):1523–36.
30 - Beaulieu JM, Robertson J, Julien JP. Interactions between peripherin and neurofilaments in cultured cells: disruption of peripherin assembly by the NF‐M and NF‐H subunits. Biochem Cell Biol. 1999;77(1):41–5.
31 - Yuan A, Sasaki T, Kumar A, Peterhoff CM, Rao MV, Liem RK, et al. Peripherin is a subunit of peripheral nerve neurofilaments: implications for differential vulnerability of CNS and PNS axons. J Neurosci. 2012 Jun 20;32(25):8501–8.
32 - Yuan A, Rao MV, Sasaki T, Chen Y, Kumar A, Veeranna null, et al. Alpha‐internexin is structurally and functionally associated with the neurofilament triplet proteins in the mature CNS. J Neurosci. 2006 Sep 27;26(39):10,006–19.
33 - Szaro BG, Strong MJ. Post‐transcriptional control of neurofilaments: new roles in development, regeneration and neurodegenerative disease. Trends Neurosci. 2010 Jan;33(1):27–37.
34 - Sternberger LA, Sternberger NH. Monoclonal antibodies distinguish phosphorylated and nonphosphorylated forms of neurofilaments in situ. Proc Natl Acad Sci USA. 1983 Oct;80(19):6126–30.
35 - Kowalczyk AP, Bornslaeger EA, Norvell SM, Palka HL, Green KJ. Desmosomes: intercellular adhesive junctions specialized for attachment of intermediate filaments. Int Rev Cytol. 1999;185:237–302.
36 - Ruhrberg C, Hajibagheri MA, Simon M, Dooley TP, Watt FM. Envoplakin, a novel precursor of the cornified envelope that has homology to desmoplakin. J Cell Biol. 1996 Aug;134(3):715–29.
37 - Stappenbeck TS, Green KJ. The desmoplakin carboxyl terminus coaligns with and specifically disrupts intermediate filament networks when expressed in cultured cells. J Cell Biol. 1992 Mar;116(5):1197–209.
38 - Yang Y, Dowling J, Yu QC, Kouklis P, Cleveland DW, Fuchs E. An essential cytoskeletal linker protein connecting actin microfilaments to intermediate filaments. Cell. 1996 Aug 23;86(4):655–65.
39 - Lariviere RC, Julien J‐P. Functions of intermediate filaments in neuronal development and disease. J Neurobiol. 2004 Jan;58(1):131–48.
40 - Goldstein ME, Sternberger NH, Sternberger LA. Phosphorylation protects neurofilaments against proteolysis. J Neuroimmunol. 1987 Mar;14(2):149–60.
41 - Gou JP, Leterrier JF. Possible involvement of ubiquitination in neurofilament degradation. Biochem Biophys Res Commun. 1995 Dec 14;217(2):529–38.
42 - Fuchs E, Cleveland DW. A structural scaffolding of intermediate filaments in health and disease. Science. 1998 Jan 23;279(5350):514–9.
43 - Helfand BT, Chang L, Goldman RD. Intermediate filaments are dynamic and motile elements of cellular architecture. J Cell Sci. 2004 Jan 15;117(Pt 2):133–41.
44 - Chang L, Goldman RD. Intermediate filaments mediate cytoskeletal crosstalk. Nat Rev Mol Cell Biol. 2004 Aug;5(8):601–13.
45 - Toivola DM, Tao G‐Z, Habtezion A, Liao J, Omary MB. Cellular integrity plus: organelle‐related and protein‐targeting functions of intermediate filaments. Trends Cell Biol. 2005 Nov;15(11):608–17.
46 - Kim S, Wong P, Coulombe PA. A keratin cytoskeletal protein regulates protein synthesis and epithelial cell growth. Nature. 2006 May 18;441(7091):362–5.
47 - Frappier T, Stetzkowski‐Marden F, Pradel LA. Interaction domains of neurofilament light chain and brain spectrin. Biochem J. 1991 Apr 15;275(Pt 2):521–7.
48 - Haddad LA, Smith N, Bowser M, Niida Y, Murthy V, Gonzalez‐Agosti C, et al. The TSC1 tumor suppressor hamartin interacts with neurofilament‐L and possibly functions as a novel integrator of the neuronal cytoskeleton. J Biol Chem. 2002 Nov 15;277(46):44,180–6.
49 - Friede RL, Samorajski T. Axon caliber related to neurofilaments and microtubules in sciatic nerve fibers of rats and mice. Anat Rec. 1970 Aug;167(4):379–87.
50 - Hoffman PN, Griffin JW, Price DL. Control of axonal caliber by neurofilament transport. J Cell Biol. 1984 Aug;99(2):705–14.
51 - Nguyen MD, Larivière RC, Julien JP. Reduction of axonal caliber does not alleviate motor neuron disease caused by mutant superoxide dismutase 1. Proc Natl Acad Sci USA. 2000 Oct 24;97(22):12,306–11.
52 - Elder GA, Friedrich VL, Bosco P, Kang C, Gourov A, Tu PH, et al. Absence of the mid‐sized neurofilament subunit decreases axonal calibers, levels of light neurofilament (NF‐L), and neurofilament content. J Cell Biol. 1998 May 4;141(3):727–39.
53 - Rao MV, Campbell J, Yuan A, Kumar A, Gotow T, Uchiyama Y, et al. The neurofilament middle molecular mass subunit carboxyl‐terminal tail domains is essential for the radial growth and cytoskeletal architecture of axons but not for regulating neurofilament transport rate. J Cell Biol. 2003 Dec 8;163(5):1021–31.
54 - Kiernan MC, Vucic S, Cheah BC, Turner MR, Eisen A, Hardiman O, et al. Amyotrophic lateral sclerosis. Lancet. 2011 Mar 12;377(9769):942–55.
55 - Hirano A. Neuropathology of ALS An overview. Neurology. 1996 Oct 1;47(4 Suppl 2):63S–66S.
56 - Letournel F, Bocquet A, Dubas F, Barthelaix A, Eyer J. Stable tubule only polypeptides (STOP) proteins co‐aggregate with spheroid neurofilaments in amyotrophic lateral sclerosis. J Neuropathol Exp Neurol. 2003 Dec;62(12):1211–9.
57 - Munoz DG, Greene C, Perl DP, Selkoe DJ. Accumulation of phosphorylated neurofilaments in anterior horn motoneurons of amyotrophic lateral sclerosis patients. J Neuropathol Exp Neurol. 1988 Jan;47(1):9–18.
58 - Troost D, Sillevis Smitt PA, de Jong JM, Swaab DF. Neurofilament and glial alterations in the cerebral cortex in amyotrophic lateral sclerosis. Acta Neuropathol. 1992;84(6):664–73.
59 - Corbo M, Hays AP. Peripherin and neurofilament protein coexist in spinal spheroids of motor neuron disease. J Neuropathol Exp Neurol. 1992 Sep;51(5):531–7.
60 - He CZ, Hays AP. Expression of peripherin in ubiquinated inclusions of amyotrophic lateral sclerosis. J Neurol Sci. 2004 Jan 15;217(1):47–54.
61 - Al‐Chalabi A, Andersen PM, Nilsson P, Chioza B, Andersson JL, Russ C, et al. Deletions of the heavy neurofilament subunit tail in amyotrophic lateral sclerosis. Hum Mol Genet. 1999 Feb;8(2):157–64.
62 - Figlewicz DA, Krizus A, Martinoli MG, Meininger V, Dib M, Rouleau GA, et al. Variants of the heavy neurofilament subunit are associated with the development of amyotrophic lateral sclerosis. Hum Mol Genet. 1994 Oct;3(10):1757–61.
63 - Gros‐Louis F, Larivière R, Gowing G, Laurent S, Camu W, Bouchard J‐P, et al. A frameshift deletion in peripherin gene associated with amyotrophic lateral sclerosis. J Biol Chem. 2004 Oct 29;279(44):45,951–6.
64 - Leung CL, He CZ, Kaufmann P, Chin SS, Naini A, Liem RKH, et al. A pathogenic peripherin gene mutation in a patient with amyotrophic lateral sclerosis. Brain Pathol. 2004 Jul;14(3):290–6.
65 - Boylan KB, Glass JD, Crook JE, Yang C, Thomas CS, Desaro P, et al. Phosphorylated neurofilament heavy subunit (pNF‐H) in peripheral blood and CSF as a potential prognostic biomarker in amyotrophic lateral sclerosis. J Neurol Neurosurg Psychiatr. 2013 Apr;84(4):467–72.
66 - Tortelli R, Ruggieri M, Cortese R, D'Errico E, Capozzo R, Leo A, et al. Elevated cerebrospinal fluid neurofilament light levels in patients with amyotrophic lateral sclerosis: a possible marker of disease severity and progression. Eur J Neurol. 2012 Dec;19(12):1561–7.
67 - Eyer J, Peterson A. Neurofilament‐deficient axons and perikaryal aggregates in viable transgenic mice expressing a neurofilament‐beta‐galactosidase fusion protein. Neuron. 1994 Feb;12(2):389–405.
68 - Letournel F, Bocquet A, Perrot R, Dechaume A, Guinut F, Eyer J, et al. Neurofilament high molecular weight‐green fluorescent protein fusion is normally expressed in neurons and transported in axons: a neuronal marker to investigate the biology of neurofilaments. Neuroscience. 2006;137(1):103–11.
69 - Zhu Q, Couillard‐Després S, Julien JP. Delayed maturation of regenerating myelinated axons in mice lacking neurofilaments. Exp Neurol. 1997 Nov;148(1):299–316.
70 - Elder GA, Friedrich VL, Margita A, Lazzarini RA. Age‐related atrophy of motor axons in mice deficient in the mid‐sized neurofilament subunit. J Cell Biol. 1999 Jul 12;146(1):181–92.
71 - Jacomy H, Zhu Q, Couillard‐Després S, Beaulieu JM, Julien JP. Disruption of type IV intermediate filament network in mice lacking the neurofilament medium and heavy subunits. J Neurochem. 1999 Sep;73(3):972–84.
72 - Levavasseur F, Zhu Q, Julien JP. No requirement of alpha‐internexin for nervous system development and for radial growth of axons. Brain Res Mol Brain Res. 1999 May 21;69(1):104–12.
73 - Larivière RC, Nguyen MD, Ribeiro‐da‐Silva A, Julien J‐P. Reduced number of unmyelinated sensory axons in peripherin null mice. J Neurochem. 2002 May;81(3):525–32.
74 - Xu Z, Cork LC, Griffin JW, Cleveland DW. Increased expression of neurofilament subunit NF‐L produces morphological alterations that resemble the pathology of human motor neuron disease. Cell. 1993 Apr 9;73(1):23–33.
75 - Wong PC, Marszalek J, Crawford TO, Xu Z, Hsieh ST, Griffin JW, et al. Increasing neurofilament subunit NF‐M expression reduces axonal NF‐H, inhibits radial growth, and results in neurofilamentous accumulation in motor neurons. J Cell Biol. 1995 Sep;130(6):1413–22.
76 - Marszalek JR, Williamson TL, Lee MK, Xu Z, Hoffman PN, Becher MW, et al. Neurofilament subunit NF‐H modulates axonal diameter by selectively slowing neurofilament transport. J Cell Biol. 1996 Nov;135(3):711–24.
77 - Julien JP, Tretjakoff I, Beaudet L, Peterson A. Expression and assembly of a human neurofilament protein in transgenic mice provide a novel neuronal marking system. Genes Dev. 1987 Dec;1(10):1085–95.
78 - Gama Sosa MA, Friedrich VL, DeGasperi R, Kelley K, Wen PH, Senturk E, et al. Human midsized neurofilament subunit induces motor neuron disease in transgenic mice. Exp Neurol. 2003 Nov;184(1):408–19.
79 - Côté F, Collard JF, Julien JP. Progressive neuronopathy in transgenic mice expressing the human neurofilament heavy gene: a mouse model of amyotrophic lateral sclerosis. Cell. 1993 Apr 9;73(1):35–46.
80 - Lee MK, Marszalek JR, Cleveland DW. A mutant neurofilament subunit causes massive, selective motor neuron death: implications for the pathogenesis of human motor neuron disease. Neuron. 1994 Oct;13(4):975–88.
81 - Ching GY, Chien CL, Flores R, Liem RK. Overexpression of alpha‐internexin causes abnormal neurofilamentous accumulations and motor coordination deficits in transgenic mice. J Neurosci. 1999 Apr 15;19(8):2974–86.
82 - Beaulieu JM, Nguyen MD, Julien JP. Late onset of motor neurons in mice overexpressing wild‐type peripherin. J Cell Biol. 1999 Nov 1;147(3):531–44.
83 - Larivière RC, Beaulieu J‐M, Nguyen MD, Julien J‐P. Peripherin is not a contributing factor to motor neuron disease in a mouse model of amyotrophic lateral sclerosis caused by mutant superoxide dismutase. Neurobiol Dis. 2003 Jul;13(2):158–66.
84 - Williamson TL, Bruijn LI, Zhu Q, Anderson KL, Anderson SD, Julien JP, et al. Absence of neurofilaments reduces the selective vulnerability of motor neurons and slows disease caused by a familial amyotrophic lateral sclerosis‐linked superoxide dismutase 1 mutant. Proc Natl Acad Sci USA. 1998 Aug 4;95(16):9631–6.
85 - Ackerley S, Grierson AJ, Brownlees J, Thornhill P, Anderton BH, Leigh PN, et al. Glutamate slows axonal transport of neurofilaments in transfected neurons. J Cell Biol. 2000 Jul 10;150(1):165–76.
86 - Manser C, Stevenson A, Banner S, Davies J, Tudor EL, Ono Y, et al. Deregulation of PKN1 activity disrupts neurofilament organisation and axonal transport. FEBS Lett. 2008 Jun 25;582(15):2303–8.
87 - Chevalier‐Larsen E, Holzbaur ELF. Axonal transport and neurodegenerative disease. Biochim Biophys Acta. 2006 Dec;1762(11–12):1094–108.
88 - Meier J, Couillard‐Després S, Jacomy H, Gravel C, Julien JP. Extra neurofilament NF‐L subunits rescue motor neuron disease caused by overexpression of the human NF‐H gene in mice. J Neuropathol Exp Neurol. 1999 Oct;58(10):1099–110.
89 - Wong NK, He BP, Strong MJ. Characterization of neuronal intermediate filament protein expression in cervical spinal motor neurons in sporadic amyotrophic lateral sclerosis (ALS). J Neuropathol Exp Neurol. 2000 Nov;59(11):972–82.
90 - Ge W‐W, Wen W, Strong W, Leystra‐Lantz C, Strong MJ. Mutant copper‐zinc superoxide dismutase binds to and destabilizes human low molecular weight neurofilament mRNA. J Biol Chem. 2005 Jan 7;280(1):118–24.
91 - Strong MJ, Volkening K, Hammond R, Yang W, Strong W, Leystra‐Lantz C, et al. TDP43 is a human low molecular weight neurofilament (hNFL) mRNA‐binding protein. Mol Cell Neurosci. 2007 Jun;35(2):320–7.
92 - Tu PH, Raju P, Robinson KA, Gurney ME, Trojanowski JQ, Lee VM. Transgenic mice carrying a human mutant superoxide dismutase transgene develop neuronal cytoskeletal pathology resembling human amyotrophic lateral sclerosis lesions. Proc Natl Acad Sci USA. 1996 Apr 2;93(7):3155–60.
93 - Eyer J, Cleveland DW, Wong PC, Peterson AC. Pathogenesis of two axonopathies does not require axonal neurofilaments. Nature. 1998 Feb 5;391(6667):584–7.
94 - Roy J, Minotti S, Dong L, Figlewicz DA, Durham HD. Glutamate potentiates the toxicity of mutant Cu/Zn‐superoxide dismutase in motor neurons by postsynaptic calcium‐dependent mechanisms. J Neurosci. 1998 Dec 1;18(23):9673–84.
95 - Ehlers MD, Fung ET, O'Brien RJ, Huganir RL. Splice variant‐specific interaction of the NMDA receptor subunit NR1 with neuronal intermediate filaments. J Neurosci. 1998 Jan 15;18(2):720–30.
96 - Nguyen MD, Larivière RC, Julien JP. Deregulation of Cdk5 in a mouse model of ALS: toxicity alleviated by perikaryal neurofilament inclusions. Neuron. 2001 Apr;30(1):135–47.
97 - Kong J, Xu Z. Overexpression of neurofilament subunit NF‐L and NF‐H extends survival of a mouse model for amyotrophic lateral sclerosis. Neurosci Lett. 2000 Mar 3;281(1):72–4.
98 - Couillard‐Després S, Zhu Q, Wong PC, Price DL, Cleveland DW, Julien JP. Protective effect of neurofilament heavy gene overexpression in motor neuron disease induced by mutant superoxide dismutase. Proc Natl Acad Sci USA. 1998 Aug 4;95(16):9626–30.