There is a need for biomarkers for amyotrophic lateral sclerosis (ALS), to support the diagnosis of the disease, to predict disease progression and to track disease activity and treatment responses. ...Over the last decade multiple studies have investigated the potential of neurofilament levels, both in cerebrospinal fluid and blood, as biomarker for ALS. The most widely studied neurofilament subunits are neurofilament light chain (NfL) and phosphorylated neurofilament heavy chain (pNfH). Neurofilament levels are reflecting neuronal injury and therefore potentially of value in ALS and other neurological disorders. In this mini-review, we summarize and discuss the available evidence about neurofilaments as diagnostic and prognostic biomarker for human ALS.
Recently, mutations in the progranulin (PGRN) gene were found to cause familial and apparently sporadic frontotemporal lobe dementia (FTLD). Moreover, missense changes in PGRN were identified in ...patients with motor neuron degeneration, a condition that is related to FTLD. Most mutations identified in patients with FTLD until now have been null mutations. However, it remains unknown whether PGRN protein levels are reduced in the central nervous system from such patients. The effects of PGRN on neurons also remain to be established. We report that PGRN levels are reduced in the cerebrospinal fluid from FTLD patients carrying a PGRN mutation. We observe that PGRN and GRN E (one of the proteolytic fragments of PGRN) promote neuronal survival and enhance neurite outgrowth in cultured neurons. These results demonstrate that PGRN/GRN is a neurotrophic factor with activities that may be involved in the development of the nervous system and in neurodegeneration.
Loss of function mutations in progranulin (GRN) cause frontotemporal dementia, but how GRN haploinsufficiency causes neuronal dysfunction remains unclear. We previously showed that GRN is ...neurotrophic in vitro. Here, we used an in vivo axonal outgrowth system and observed a delayed recovery in GRN-/- mice after facial nerve injury. This deficit was rescued by reintroduction of human GRN and relied on its C-terminus and on neuronal GRN production. Transcriptome analysis of the facial motor nucleus post injury identified cathepsin D (CTSD) as the most upregulated gene. In aged GRN-/- cortices, CTSD was also upregulated, but the relative CTSD activity was reduced and improved upon exogenous GRN addition. Moreover, GRN and its C-terminal granulin domain granulinE (GrnE) both stimulated the proteolytic activity of CTSD in vitro. Pull-down experiments confirmed a direct interaction between GRN and CTSD. This interaction was also observed with GrnE and stabilized the CTSD enzyme at different temperatures. Investigating the importance of this interaction for axonal regeneration in vivo we found that, although individually tolerated, a combined reduction of GRN and CTSD synergistically reduced axonal outgrowth. Our data links the neurotrophic effect of GRN and GrnE with a lysosomal chaperone function on CTSD to maintain its proteolytic capacity.
Neurodegenerative diseases are characterized by the presence of protein inclusions with a different protein content depending on the type of disease. Amyotrophic lateral sclerosis (ALS) and ...frontotemporal lobar degeneration (FTLD) are no exceptions to this common theme. In most ALS and FTLD cases, the predominant pathological species are RNA-binding proteins. Interestingly, these proteins are both depleted from their normal nuclear localization and aggregated in the cytoplasm. This key pathological feature has suggested a potential dual mechanism with both nuclear loss of function and cytoplasmic gain of function being at play. Yet, why and how this pathological cascade is initiated in most patients, and especially sporadic cases, is currently unresolved. Recent breakthroughs in
C9orf72
ALS/FTLD disease models point at a pivotal role for the nuclear transport system in toxicity. To address whether defects in nuclear transport are indeed implicated in the disease, we reviewed two decades of ALS/FTLD literature and combined this with bioinformatic analyses. We find that both RNA-binding proteins and nuclear transport factors are key players in ALS/FTLD pathology. Moreover, our analyses suggest that disturbances in nucleocytoplasmic transport play a crucial initiating role in the disease, by bridging both nuclear loss and cytoplasmic gain of functions. These findings highlight this process as a novel and promising therapeutic target for ALS and FTLD.
Amyotrophic lateral sclerosis (ALS) is a neurodegenerative disorder that primarily affects the motor system and presents with progressive muscle weakness. Most patients survive for only 2-5 years ...after disease onset, often due to failure of the respiratory muscles. ALS is a familial disease in ∼10% of patients, with the remaining 90% developing sporadic ALS. Over the past decade, major advances have been made in our understanding of the genetics and neuropathology of ALS. To date, around 20 genes are associated with ALS, with the most common causes of typical ALS associated with mutations in
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Advances in our understanding of the genetic basis of ALS have led to the creation of different models of this disease. The molecular pathways that have emerged from these systems are more heterogeneous than previously anticipated, ranging from protein aggregation and defects in multiple key cellular processes in neurons, to dysfunction of surrounding non-neuronal cells. Here, we review the different model systems used to study ALS and discuss how they have contributed to our current knowledge of ALS disease mechanisms. A better understanding of emerging disease pathways, the detrimental effects of the various gene mutations and the causes underlying motor neuron denegation in sporadic ALS will accelerate progress in the development of novel treatments.
Objective:
Early and accurate diagnosis of amyotrophic lateral sclerosis (ALS) is important for patient care and for entry in clinical trials. Retrospective studies suggest that the use of the Awaji ...algorithm for the diagnosis of ALS is more sensitive for early diagnosis than the currently used revised El Escorial criteria.
Methods:
We prospectively compared the revised El Escorial criteria with the Awaji algorithm in patients seen with suspected ALS at the University Hospitals Leuven between January 2008 and April 2010.
Results:
Out of 200 patients referred for the diagnosis of ALS, 66% and 85% could be categorized to definite or probable ALS at first presentation according to the revised El Escorial and the Awaji algorithm, respectively (p < 5.6 × 10−17). This corresponds to a >50% reduction of patients not eligible for clinical trial entry. Application of the Awaji algorithm made the diagnosis of ALS more likely by at least 1 diagnostic category in 25.7% of patients and identified at least 1 additional region with electrodiagnostic signs of ongoing lower motor neuron loss in 46.4% of electrodiagnostic investigations. Application of the Awaji algorithm did not result in a single false‐positive diagnosis of ALS in this study.
Interpretation:
Our data demonstrate that the Awaji algorithm is significantly more sensitive compared to the revised El Escorial criteria, without resulting in false‐positive diagnoses of ALS. It should therefore be used in clinical trials. Ann Neurol 2011;
Amyotrophic lateral sclerosis (ALS) is a late-onset devastating degenerative disease mainly affecting motor neurons. Motor neuron degeneration is accompanied and aggravated by oligodendroglial ...pathology and the presence of reactive astrocytes and microglia. We studied the role of the Notch signaling pathway in ALS, as it is implicated in several processes that may contribute to this disease, including axonal retraction, microgliosis, astrocytosis, oligodendrocyte precursor cell proliferation and differentiation, and cell death. We observed abnormal activation of the Notch signaling pathway in the spinal cord of SOD1G93A mice, a well-established model for ALS, as well as in the spinal cord of patients with sporadic ALS (sALS). This increased activation was particularly evident in reactive GFAP-positive astrocytes. In addition, one of the main Notch ligands, Jagged-1, was ectopically expressed in reactive astrocytes in spinal cord from ALS mice and patients, but absent in resting astrocytes. Astrocyte-specific inactivation of Jagged-1 in presymptomatic SOD1G93A mice further exacerbated the activation of the Notch signaling pathway and aggravated the course of the disease in these animals without affecting disease onset. These data suggest that aberrant Notch signaling activation contributes to the pathogenesis of ALS, both in sALS patients and SOD1G93A mice, and that it is mitigated in part by the upregulation of astrocytic Jagged-1.
•The Notch pathway is overactive in spinal cords of sALS patients and ALS mice.•Reactive astrocytes from sALS patients and ALS mice overexpress Jagged-1 and NICD-1.•Astrocyte-specific inactivation of Jagged-1 accelerates disease progression in ALS mice, after onset.•Jagged-1 inactivation in astrocytes enhances Notch signaling activation in ALS mice.•Reactive astrocytes express Jagged-1 to limit Notch activation by cis-inhibition.
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