Amyotrophic Lateral Sclerosis Fibroblasts Research Articles

Gene expression profiles in sporadic ALS fibroblasts define disease subtypes and the metabolic effects of the investigational drug EH301.

Metabolic alterations shared between the nervous system and skin fibroblasts have emerged in amyotrophic lateral sclerosis (ALS). Recently, we found that a subgroup of sporadic ALS (sALS) fibroblasts (sALS1) is characterized by metabolic profiles distinct from other sALS cases (sALS2) and controls, suggesting that metabolic therapies could be effective in sALS. The metabolic modulators nicotinamide riboside and pterostilbene (EH301) are under clinical development for the treatment of ALS. Here, we studied the transcriptome and metabolome of sALS cells to understand the molecular bases of sALS metabotypes and the impact of EH301. Metabolomics and transcriptomics were investigated at baseline and after EH301 treatment. Moreover, weighted gene coexpression network analysis (WGCNA) was used to investigate the association of the metabolic and clinical features. We found that the sALS1 transcriptome is distinct from sALS2 and that EH301 modifies gene expression differently in sALS1, sALS2 and the controls. Furthermore, EH301 had strong protective effects against metabolic stress, an effect linked to the antiinflammatory and antioxidant pathways. WGCNA revealed that the ALS functional rating scale and metabotypes are associated with gene modules enriched for the cell cycle, immunity, autophagy and metabolic genes, which are modified by EH301. The meta-analysis of publicly available transcriptomic data from induced motor neurons by Answer ALS confirmed the functional associations of genes correlated with disease traits. A subset of genes differentially expressed in sALS fibroblasts was used in a machine learning model to predict disease progression. In conclusion, multiomic analyses highlighted the differential metabolic and transcriptomic profiles in patient-derived fibroblast sALS, which translate into differential responses to the investigational drug EH301.

Targeting S100A4 with niclosamide attenuates inflammatory and profibrotic pathways in models of amyotrophic lateral sclerosis

BackgroundAn increasing number of studies evidences that amyotrophic lateral sclerosis (ALS) is characterized by extensive alterations in different cell types and in different regions besides the CNS. We previously reported the upregulation in ALS models of a gene called fibroblast-specific protein-1 or S100A4, recognized as a pro-inflammatory and profibrotic factor. Since inflammation and fibrosis are often mutual-sustaining events that contribute to establish a hostile environment for organ functions, the comprehension of the elements responsible for these interconnected pathways is crucial to disclose novel aspects involved in ALS pathology.MethodsHere, we employed fibroblasts derived from ALS patients harboring the C9orf72 hexanucleotide repeat expansion and ALS patients with no mutations in known ALS-associated genes and we downregulated S100A4 using siRNA or the S100A4 transcriptional inhibitor niclosamide. Mice overexpressing human FUS were adopted to assess the effects of niclosamide in vivo on ALS pathology.ResultsWe demonstrated that S100A4 underlies impaired autophagy and a profibrotic phenotype, which characterize ALS fibroblasts. Indeed, its inhibition reduces inflammatory, autophagic, and profibrotic pathways in ALS fibroblasts, and interferes with different markers known as pathogenic in the disease, such as mTOR, SQSTM1/p62, STAT3, α-SMA, and NF-κB. Importantly, niclosamide in vivo treatment of ALS-FUS mice reduces the expression of S100A4, α-SMA, and PDGFRβ in the spinal cord, as well as gliosis in central and peripheral nervous tissues, together with axonal impairment and displays beneficial effects on muscle atrophy, by promoting muscle regeneration and reducing fibrosis.ConclusionOur findings show that S100A4 has a role in ALS-related mechanisms, and that drugs such as niclosamide which are able to target inflammatory and fibrotic pathways could represent promising pharmacological tools for ALS.

Amyotrophic lateral sclerosis alters the metabolic aging profile in patient derived fibroblasts

Aging is a major risk factor for neurodegenerative diseases, including amyotrophic lateral sclerosis (ALS). As metabolic alterations are a hallmark of aging and have previously been observed in ALS, it is important to examine the effect of aging in the context of ALS metabolic function. Here, using a newly established phenotypic metabolic approach, we examined the effect of aging on the metabolic profile of fibroblasts derived from ALS cases compared to controls. We found that ALS fibroblasts have an altered metabolic profile, which is influenced by age. In control cases, we found significant increases with age in NADH metabolism in the presence of several metabolites including lactic acid, trehalose, uridine and fructose, which was not recapitulated in ALS cases. Conversely, we found a reduction of NADH metabolism with age of biopsy, age of onset and age of death in the presence of glycogen in the ALS cohort. Furthermore, we found that NADH production correlated with disease progression rates in relation to a number of metabolites including inosine and α-ketoglutaric acid. Inosine or α-ketoglutaric acid supplementation in ALS fibroblasts was bioenergetically favourable. Overall, we found aging related defects in energy substrates that feed carbon into glycolysis at various points as well as the tricarboxylic acid (TCA) cycle in ALS fibroblasts, which was validated in induced neuronal progenitor cell derived iAstrocytes. Our results suggest that supplementing those pathways may protect against age related metabolic dysfunction in ALS.

Hsp90-mediated regulation of DYRK3 couples stress granule disassembly and growth via mTORC1 signaling.

Stress granules (SGs) are dynamic condensates associated with protein misfolding diseases. They sequester stalled mRNAs and signaling factors, such as the mTORC1 subunit raptor, suggesting that SGs coordinate cell growth during and after stress. However, the molecular mechanisms linking SG dynamics and signaling remain undefined. We report that the chaperone Hsp90 is required for SG dissolution. Hsp90 binds and stabilizes the dual‐specificity tyrosine‐phosphorylation‐regulated kinase 3 (DYRK3) in the cytosol. Upon Hsp90 inhibition, DYRK3 dissociates from Hsp90 and becomes inactive. Inactive DYRK3 is subjected to two different fates: it either partitions into SGs, where it is protected from irreversible aggregation, or it is degraded. In the presence of Hsp90, DYRK3 is active and promotes SG disassembly, restoring mTORC1 signaling and translation. Thus, Hsp90 links stress adaptation and cell growth by regulating the activity of a key kinase involved in condensate disassembly and translation restoration.

Chronic stress induces formation of stress granules and pathological TDP-43 aggregates in human ALS fibroblasts and iPSC-motoneurons

Amyotrophic lateral sclerosis (ALS) and frontotemporal dementia (FTD) are fatal neurodegenerative diseases characterized by the presence of neuropathological aggregates of phosphorylated TDP-43 (P-TDP-43) protein. The RNA-binding protein TDP-43 participates also to cell stress response by forming stress granules (SG) in the cytoplasm to temporarily arrest translation. The hypothesis that TDP-43 pathology directly arises from SG has been proposed but is still under debate because only sub-lethal stress conditions have been tested experimentally so far. In this study we reproduced a mild and chronic oxidative stress by sodium arsenite to better mimic the persistent and subtle alterations occurring during the neurodegenerative process in primary fibroblasts and induced pluripotent stem cell-derived motoneurons (iPSC-MN) from ALS patients carrying mutations in TARDBP and C9ORF72 genes. We found that not only the acute sub-lethal stress usually used in literature, but also the chronic oxidative insult was able to induce SG formation in both primary fibroblasts and iPSC-MN. We also observed the recruitment of TDP-43 into SG only upon chronic stress in association to the formation of distinct cytoplasmic P-TDP-43 aggregates and a significant increase of the autophagy marker p62. A quantitative analysis revealed differences in both the number of cells forming SG in mutant ALS and healthy control fibroblasts, suggesting a specific genetic contribution to cell stress response, and in SG size, suggesting a different composition of these cytoplasmic foci in the two stress conditions. Upon removal of arsenite, the recovery from chronic stress was complete for SG and P-TDP-43 aggregates at 72 h with the exception of p62, which was reduced but still persistent, supporting the hypothesis that autophagy impairment may drive pathological TDP-43 aggregates formation. The gene-specific differences observed in fibroblasts in response to oxidative stress were not present in iPSC-MN, which showed a similar formation of SG and P-TDP-43 aggregates regardless their genotype. Our results show that SG and P-TDP-43 aggregates may be recapitulated in patient-derived neuronal and non-neuronal cells exposed to prolonged oxidative stress, which may be therefore exploited to study TDP-43 pathology and to develop individualized therapeutic strategies for ALS/FTD.

ALS skin fibroblasts reveal oxidative stress and ERK1/2-mediated cytoplasmic localization of TDP-43

The main hallmark of many forms of familiar and sporadic amyotrophic lateral sclerosis (ALS) is a reduction in nuclear TDP-43 protein and its inclusion in cytoplasmic aggregates in motor neurons. In order to understand which cellular and molecular mechanisms underlie the mislocalization of TDP-43, we examined human skin fibroblasts from two individuals with familial ALS, both with mutations in TDP-43, and two individuals with sporadic ALS, both without TDP-43 mutations or mutations in other ALS related genes. We found that all ALS fibroblasts had a partially cytoplasmic localization of TDP-43 and had reduced cell metabolism as compared to fibroblasts from apparently healthy individuals. ALS fibroblasts showed an increase in global protein synthesis and an increase in 4E-BP1 and rpS6 phosphorylation, which is indicative of mTORC1 activity. We also observed a decrease in glutathione (GSH), which suggests that oxidative stress is elevated in ALS. ERK1/2 activity regulated the extent of oxidative stress and the localization of TDP-43 in the cytoplasm in all ALS fibroblasts. Lastly, ALS fibroblasts showed reduced stress granule formation in response to H2O2 stress. In conclusion, these findings identify specific cellular and molecular defects in ALS fibroblasts, thus providing insight into potential mechanisms that may also occur in degenerating motor neurons.

Metabo-lipidomics of Fibroblasts and Mitochondrial-Endoplasmic Reticulum Extracts from ALS Patients Shows Alterations in Purine, Pyrimidine, Energetic, and Phospholipid Metabolisms.

Amyotrophic lateral sclerosis (ALS) is characterized by a wide metabolic remodeling, as shown by recent metabolomics and lipidomics studies performed in samples from patient cohorts and experimental animal models. Here, we explored the metabolome and lipidome of fibroblasts from sporadic ALS patients (n = 13) comparatively to age- and sex-matched controls (n = 11), and the subcellular fraction containing the mitochondria and endoplasmic reticulum (mito-ER), given that mitochondrial dysfunctions and ER stress are important features of ALS patho-mechanisms. We also assessed the mitochondrial oxidative respiration and the mitochondrial genomic (mtDNA) sequence, although without yielding significant differences. Compared to controls, ALS fibroblasts did not exhibit a mitochondrial respiration defect nor an increased proportion of mitochondrial DNA mutations. In addition, non-targeted metabolomics and lipidomics analyses identified 124 and 127 metabolites, and 328 and 220 lipids in whole cells and the mito-ER fractions, respectively, along with partial least-squares-discriminant analysis (PLS-DA) models being systematically highly predictive of the disease. The most discriminant metabolomic features were the alteration of purine, pyrimidine, and energetic metabolisms, suggestive of oxidative stress and of pro-inflammatory status. The most important lipidomic feature in the mito-ER fraction was the disturbance of phosphatidylcholine PC (36:4p) levels, which we had previously reported in the cerebrospinal fluid of ALS patients and in the brain from an ALS mouse model. Thus, our results reveal that fibroblasts from sporadic ALS patients share common metabolic remodeling, consistent with other metabolic studies performed in ALS, opening perspectives for further exploration in this cellular model in ALS.

CMT AND NEUROGENIC DISEASE: P.346Small molecule image-based screen identifies modulators of PML nuclear body phenotype in ALS models

Dominant mutations in the gene encoding the nucleic acid binding protein FUS cause ∼5% of familial amyotrophic lateral sclerosis (ALS). While some FUS mutants mislocalize to the cytoplasm due to disruption of a nuclear localization sequence, many remain predominantly nuclear and may exert a gain of toxicity within the nucleus. We seek to discern the mechanism(s) by which FUS mutants ultimately injure aging motor neurons and to develop effective therapeutic approaches to defend against these insults. We identified a novel and robust nuclear phenotype caused by FUS mutants: impaired stress-responsive processing of sub-nuclear assemblies known as promyelocytic leukemia (PML) nuclear bodies. PML nuclear bodies occur in many cell types (including CNS and muscle) and mediate stress-responsive regulation of nuclear protein homeostasis, transcription, DNA-damage pathways, and cellular senescence, yet their potential role in ALS has not been explored. We observed that PML bodies were abnormally enlarged both in cell lines and in human ALS fibroblasts expressing mutant FUS. Exposure to mild oxidative stress or proteasome inhibition aggravated this phenotype in FUS mutant cells. We developed a high-content imaging-based assay to screen for small molecule compounds that exacerbate or ameliorate the PML body abnormality. Using the LOPAC library of 1,280 pharmacologically active compounds, we identified a set of hits that implicate impaired cellular redox homeostasis as an important determinant of the phenotype and confirmed this using human ALS fibroblasts. We have established transgenic mice harboring ALS-linked FUS variants and observed age-dependent loss of the connection between motor nerves and muscle in mice that express the hFUS-R495X mutant. We are using a lentiviral reporter to test whether a subset of the prioritized hit compounds modulate defects of nuclear protein homeostasis in cultured primary neurons, glia, or muscle cells obtained from FUS mutant mice.

TLQP Peptides in Amyotrophic Lateral Sclerosis: Possible Blood Biomarkers with a Neuroprotective Role

While the VGF-derived TLQP peptides have been shown to prevent neuronal apoptosis, and to act on synaptic strengthening, their involvement in Amyotrophic Lateral Sclerosis (ALS) remains unclarified. We studied human ALS patients’ plasma (taken at early to late disease stages) and primary fibroblast cultures (patients vs controls), in parallel with SOD1-G93A transgenic mice (taken at pre-, early- and late symptomatic stages) and the mouse motor neuron cell line (NSC-34) treated with Sodium Arsenite (SA) to induce oxidative stress. TLQP peptides were measured by enzyme-linked immunosorbent assay, in parallel with gel chromatography characterization, while their localization was studied by immunohistochemistry. In controls, TLQP peptides, including forms compatible with TLQP-21 and 62, were revealed in plasma and spinal cord motor neurons, as well as in fibroblasts and NSC-34 cells. TLQP peptides were reduced in ALS patients’ plasma starting in the early disease stage (14% of controls) and remaining so at the late stage (16% of controls). In mice, a comparable pattern of reduction was shown (vs wild type), in both plasma and spinal cord already in the pre-symptomatic phase (about 26% and 70%, respectively). Similarly, the levels of TLQP peptides were reduced in ALS fibroblasts (31% of controls) and in the NSC-34 treated with Sodium Arsenite (53% of decrease), however, the exogeneous TLQP-21 improved cell viability (SA-treated cells with TLQP-21, vs SA-treated cells only: about 83% vs. 75%). Hence, TLQP peptides, reduced upon oxidative stress, are suggested as blood biomarkers, while TLQP-21 exerts a neuroprotective activity.

Fibroblast bioenergetics to classify amyotrophic lateral sclerosis patients

BackgroundThe objective of this study was to investigate cellular bioenergetics in primary skin fibroblasts derived from patients with amyotrophic lateral sclerosis (ALS) and to determine if they can be used as classifiers for patient stratification.MethodsWe assembled a collection of unprecedented size of fibroblasts from patients with sporadic ALS (sALS, n = 171), primary lateral sclerosis (PLS, n = 34), ALS/PLS with C9orf72 mutations (n = 13), and healthy controls (n = 91). In search for novel ALS classifiers, we performed extensive studies of fibroblast bioenergetics, including mitochondrial membrane potential, respiration, glycolysis, and ATP content. Next, we developed a machine learning approach to determine whether fibroblast bioenergetic features could be used to stratify patients.ResultsCompared to controls, sALS and PLS fibroblasts had higher average mitochondrial membrane potential, respiration, and glycolysis, suggesting that they were in a hypermetabolic state. Only membrane potential was elevated in C9Orf72 lines. ATP steady state levels did not correlate with respiration and glycolysis in sALS and PLS lines. Based on bioenergetic profiles, a support vector machine (SVM) was trained to classify sALS and PLS with 99% specificity and 70% sensitivity.ConclusionssALS, PLS, and C9Orf72 fibroblasts share hypermetabolic features, while presenting differences of bioenergetics. The absence of correlation between energy metabolism activation and ATP levels in sALS and PLS fibroblasts suggests that in these cells hypermetabolism is a mechanism to adapt to energy dissipation. Results from SVM support the use of metabolic characteristics of ALS fibroblasts and multivariate analysis to develop classifiers for patient stratification.

FUS Mutant Human Motoneurons Display Altered Transcriptome and microRNA Pathways with Implications for ALS Pathogenesis.

SummaryThe FUS gene has been linked to amyotrophic lateral sclerosis (ALS). FUS is a ubiquitous RNA-binding protein, and the mechanisms leading to selective motoneuron loss downstream of ALS-linked mutations are largely unknown. We report the transcriptome analysis of human purified motoneurons, obtained from FUS wild-type or mutant isogenic induced pluripotent stem cells (iPSCs). Gene ontology analysis of differentially expressed genes identified significant enrichment of pathways previously associated to sporadic ALS and other neurological diseases. Several microRNAs (miRNAs) were also deregulated in FUS mutant motoneurons, including miR-375, involved in motoneuron survival. We report that relevant targets of miR-375, including the neural RNA-binding protein ELAVL4 and apoptotic factors, are aberrantly increased in FUS mutant motoneurons. Characterization of transcriptome changes in the cell type primarily affected by the disease contributes to the definition of the pathogenic mechanisms of FUS-linked ALS.

Gene expression profiles and protein-protein interaction networks in amyotrophic lateral sclerosis patients with C9orf72 mutation.

BackgroundAmyotrophic lateral sclerosis (ALS) is a neurodegenerative disease that involves the death of neurons. ALS is associated with many gene mutations as previously studied. In order to explore the molecular mechanisms underlying ALS with C9orf72 mutation, gene expression profiles of ALS fibroblasts and control fibroblasts were subjected to bioinformatics analysis. Genes with critical functional roles can be detected by a measure of node centrality in biological networks. In gene co-expression networks, highly connected genes called as candidate hubs have been associated with key disease-related pathways. Herein, this method was applied to find the hub genes related to ALS disease.MethodsIllumina HiSeq microarray gene expression dataset GSE51684 was retrieved from Gene Expression Omnibus (GEO) database which included four Sporadic ALS, twelve Familial ALS and eight control samples. Differentially Expressed Genes (DEGs) were identified using the Student’s t test statistical method and gene co-expression networking. Gene ontology (GO) function and KEGG pathway enrichment analysis of DEGs were performed using the DAVID online tool. Protein-protein interaction (PPI) networks were constructed by mapping the DEGs onto protein-protein interaction data from publicly available databases to identify the pathways where DEGs are involved in. PPI interaction network was divided into subnetworks using MCODE algorithm and was analyzed using Cytoscape.ResultsThe results revealed that the expression of DEGs was mainly involved in cell adhesion, cell-cell signaling, Extra cellular matrix region GO processes and focal adhesion, neuroactive ligand receptor interaction, Extracellular matrix receptor interaction. Tumor necrosis factor (TNF), Endothelin 1 (EDN1), Angiotensin (AGT) and many cell adhesion molecules (CAM) were detected as hub genes that can be targeted as novel therapeutic targets for ALS disease.ConclusionThese analyses and findings enhance the understanding of ALS pathogenesis and provide references for ALS therapy.Electronic supplementary materialThe online version of this article (doi:10.1186/s13023-016-0531-y) contains supplementary material, which is available to authorized users.

Identification of Apo B48 and other novel biomarkers in amyotrophic lateral sclerosis patient fibroblasts.

Amyotrophic lateral sclerosis (ALS) is a debilitating fatal neurodegenerative disorder. 90-95% of ALS cases are sporadic with no clear risk factors associated with the disease. Identification of biomarkers associated with ALS may lead to early detection and make it more amenable to therapeutic intervention. SILAC was used to quantitatively analyze the proteomes of ALS and control human fibroblasts. Out of total of 861 proteins identified, 33 were found to be differentially regulated. ApoB48 and Hsp20 were downregulated, while Fibulin-1 was upregulated. We report the differential regulation of these proteins in ALS fibroblasts, and their potential as novel biomarkers and possible drug targets for ALS.

Bioenergetic markers in skin fibroblasts of sporadic amyotrophic lateral sclerosis and progressive lateral sclerosis patients.

Energy metabolism could influence amyotrophic lateral sclerosis (ALS) and progressive lateral sclerosis (PLS) pathogenesis and the response to therapy. We developed a novel assay to simultaneously assess mitochondrial content and membrane potential in patients' skin fibroblasts. In ALS and PLS fibroblasts, membrane potential was increased and mitochondrial content decreased, relative to healthy controls. In ALS higher mitochondrial membrane potential correlated with age at diagnosis, and in PLS it correlated with disease severity. These unprecedented findings in ALS and PLS fibroblasts could shed new light onto disease pathogenesis and help in developing biomarkers to predict disease evolution and the individual response to therapy in motor neuron diseases.

Superoxide dismutase 1 mutation in a cellular model of amyotrophic lateral sclerosis shifts energy generation from oxidative phosphorylation to glycolysis

Amyotrophic lateral sclerosis (ALS) is a fatal neurodegenerative disorder involving the progressive degeneration of motor neurons in the brain and spinal cord. Mitochondrial dysfunction plays a key role in ALS disease progression and has been observed in several ALS cellular and animal models. Here, we show that fibroblasts isolated from ALS cases with a Cu/Zn superoxide dismutase (SOD1) I113T mutation recapitulate these mitochondrial defects. Using a novel technique, which measures mitochondrial respiration and glycolytic flux simultaneously in living cells, we have shown that SOD1 mutation causes a reduction in mitochondrial respiration and an increase in glycolytic flux. This causes a reduction in adenosine triphosphate produced by oxidative phosphorylation and an increase in adenosine triphosphate produced by glycolysis. Switching the energy source from glucose to galactose caused uncoupling of mitochondria with increased proton leak in SOD1I113T fibroblasts. Assessment of the contribution of fatty acid oxidation to total respiration, suggested that fatty acid oxidation is reduced in SOD1 ALS fibroblasts, an effect which can be mimicked by starving the control cells of glucose. These results highlight the importance of understanding the interplay between the major metabolic pathways, which has the potential to lead to strategies to correct the metabolic dysregulation observed in ALS cases.

SOD1 mRNA expression in sporadic amyotrophic lateral sclerosis

The mutated Cu,Zn-superoxide dismutase gene (SOD1) (E.C. No. 1.15.1.1) is generally recognized as a pathological cause of 20% of the familial form of Amyotrophic Lateral Sclerosis (ALS). However, several pieces of evidence also show that wild-type SOD1, under conditions of cellular stress, is implicated in a significant fraction of sporadic ALS cases, which represent 90% of ALS patients. Herein, we describe an abnormally high level of SOD1 transcript in spinal cord, brain stem and lymphocytes of sporadic ALS patients. Protein expression studies show a similar or lower amount of SOD1 in affected brain areas and lymphocytes, respectively. No differences are found in brain regions (cerebellum and non-motor cerebral cortex) not involved in the ALS neurodegenerative processes. In this report, cell and disease specificity are shown since no mRNA SOD1 increase is observed in sporadic ALS fibroblasts or in lymphocytes of patients affected by Alzheimer's disease. These findings provide new insight and understanding of the pathologic causes of sporadic forms of ALS and allow a possible explanation for the molecular involvement of wild-type SOD1.

Calcium homeostasis in fibroblasts from patients with amyotrophic lateral sclerosis

Amyotrophic lateral sclerosis (ALS) is a chronic neurodegenerative disorder of the motor system in the CNS characterized by motor neuron death in the spinal cord, brain stem and cortex. Readily available tissues such as fibroblasts from ALS patients can serve as simple model systems to study the molecular mechanisms leading to degenerative disorders. We have used Fura-2 fluorescence microscopy and single-cell imaging to study the spatiotemporal dynamics of intracellular free calcium ([Ca 2+] i) in primary cultures of fibroblasts from skin biopsies from ALS and normal subjects. Increases in [Ca 2+] i were induced by stimulation with bradykinin (100 nM); neurotensin (50 nM); N-formyl-Met-Leu-Phe (chemotactic peptide) (1 μM); [Arg 8]-vasopressin (1 μM) and histamine (10 μM). The levels of [Ca 2+] i in 80–120 individual cells per agonist were monitored for 15 min. No significant differences were found in the resting levels of [Ca 2+] i in control (102 ± 4 nM) and ALS (98 ± 6 nM) fibroblasts and in the maximal [Ca 2+] i levels after stimulation with N-formyl-Met-Leu-Phe, [Arg 8]-vasopressin, and histamine. Significantly lower [Ca 2+] i transients were found in fibroblasts from ALS donors compared to controls when stimulated with neurotensin ( p < 0.002) and bradykinin ( p < 0.005). The percentage of individual cells reacting to a given agonist (40–100%) was similar in both groups. The molecular basis of the impaired calcium homeostasis in fibroblasts from ALS patients is not known, but a generalized membrane defect can be excluded since the [Ca 2+] i responses are defective only when bradykinin or neurotensin are used as agonists.