Generation of a heterozygous and a homozygous CSF1R knockout line from iPSC using CRISPR/Cas9.

Mutations in Colony-stimulating factor 1 receptor (CSF1R) lead to CSF1R-related leukoencephalopathy, also known as Adult-onset leukoencephalopathy with axonal spheroids and pigmented glia (ALSP), a rapidly progressing neurodegenerative disease with severe cognitive and motor impairment. In this study, a homozygous and a heterozygous CSF1R knockout induced pluripotent stem cell (iPSC) line were generated by CRISPR/Cas9-based gene editing. These in vitro models will provide a helpful tool for investigating the still largely unknown pathophysiology of CSF1R-related leukoencephalopathy.

Prediction of the disease course in Friedreich ataxia.

We explored whether disease severity of Friedreich ataxia can be predicted using data from clinical examinations. From the database of the European Friedreich Ataxia Consortium for Translational Studies (EFACTS) data from up to five examinations of 602 patients with genetically confirmed FRDA was included. Clinical instruments and important symptoms of FRDA were identified as targets for prediction, while variables such as genetics, age of disease onset and first symptom of the disease were used as predictors. We used modelling techniques including generalised linear models, support-vector-machines and decision trees. The scale for rating and assessment of ataxia (SARA) and the activities of daily living (ADL) could be predicted with predictive errors quantified by root-mean-squared-errors (RMSE) of 6.49 and 5.83, respectively. Also, we were able to achieve reasonable performance for loss of ambulation (ROC-AUC score of 0.83). However, predictions for the SCA functional assessment (SCAFI) and presence of cardiological symptoms were difficult. In conclusion, we demonstrate that some clinical features of FRDA can be predicted with reasonable error; being a first step towards future clinical applications of predictive modelling. In contrast, targets where predictions were difficult raise the question whether there are yet unknown variables driving the clinical phenotype of FRDA.

Chitotriosidase is a biomarker for adult-onset leukoencephalopathy with axonal spheroids and pigmented glia.

Adult-onset leukoencephalopathy with axonal spheroids and pigmented glia (ALSP) leads to rapidly progressive dementia and is caused by mutations in the gene CSF1R. Neurodegeneration is driven by dysfunction of microglia, the predominant cell type expressing CSF1R in the brain. We assessed chitotriosidase, an enzyme secreted by microglia, in serum and cerebrospinal fluid of patients with ALSP. Chitotriosidase activity was highly increased in cerebrospinal fluid of patients and correlated inversely with disease duration. Of interest, presymptomatic CSF1R mutation carriers did not show elevated chitotriosidase levels. This makes chitotriosidase a promising new biomarker of disease activity for this rare disease.

Heterozygous UCHL1 loss-of-function variants cause a neurodegenerative disorder with spasticity, ataxia, neuropathy, and optic atrophy.

PURPOSE: Biallelic variants in UCHL1 have been associated with a progressive early-onset neurodegenerative disorder, autosomal recessive spastic paraplegia type 79. In this study, we investigated heterozygous UCHL1 variants on the basis of results from cohort-based burden analyses. METHODS: Gene-burden analyses were performed on exome and genome data of independent cohorts of patients with hereditary ataxia and spastic paraplegia from Germany and the United Kingdom in a total of 3169 patients and 33,141 controls. Clinical data of affected individuals and additional independent families were collected and evaluated. Patients' fibroblasts were used to perform mass spectrometry-based proteomics. RESULTS: UCHL1 was prioritized in both independent cohorts as a candidate gene for an autosomal dominant disorder. We identified a total of 34 cases from 18 unrelated families, carrying 13 heterozygous loss-of-function variants (15 families) and an inframe insertion (3 families). Affected individuals mainly presented with spasticity (24/31), ataxia (28/31), neuropathy (11/21), and optic atrophy (9/17). The mass spectrometry-based proteomics showed approximately 50% reduction of UCHL1 expression in patients' fibroblasts. CONCLUSION: Our bioinformatic analysis, in-depth clinical and genetic workup, and functional studies established haploinsufficiency of UCHL1 as a novel disease mechanism in spastic ataxia.

Progression characteristics of the European Friedreich's Ataxia Consortium for Translational Studies (EFACTS): a 4-year cohort study.

BACKGROUND: The European Friedreich's Ataxia Consortium for Translational Studies (EFACTS) investigates the natural history of Friedreich's ataxia. We aimed to assess progression characteristics and to identify patient groups with differential progression rates based on longitudinal 4-year data to inform upcoming clinical trials in Friedreich's ataxia. METHODS: EFACTS is a prospective, observational cohort study based on an ongoing and open-ended registry. Patients with genetically confirmed Friedreich's ataxia were seen annually at 11 clinical centres in seven European countries (Austria, Belgium, France, Germany, Italy, Spain, and the UK). Data from baseline to 4-year follow-up were included in the current analysis. Our primary endpoints were the Scale for the Assessment and Rating of Ataxia (SARA) and the activities of daily living (ADL). Linear mixed-effect models were used to analyse annual disease progression for the entire cohort and subgroups defined by age of onset and ambulatory abilities. Power calculations were done for potential trial designs. This study is registered with ClinicalTrials.gov, NCT02069509. FINDINGS: Between Sept 15, 2010, and Nov 20, 2018, of 914 individuals assessed for eligibility, 602 patients were included. Of these, 552 (92%) patients contributed data with at least one follow-up visit. Annual progression rate for SARA was 0·82 points (SE 0·05) in the overall cohort, and higher in patients who were ambulatory (1·12 [0·07]) than non-ambulatory (0·50 [0·07]). ADL worsened by 0·93 (SE 0·05) points per year in the entire cohort, with similar progression rates in patients who were ambulatory (0·94 [0·07]) and non-ambulatory (0·91 [0·08]). Although both SARA and ADL showed slightly greater worsening in patients with typical onset (symptom onset at ≤24 years) than those with late onset (symptom onset ≥25 years), differences in progression slopes were not significant. For a 2-year parallel-group trial, 230 (115 per group) patients would be required to detect a 50% reduction in SARA progression at 80% power: 118 (59 per group) if only individuals who are ambulatory are included. With ADL as the primary outcome, 190 (95 per group) patients with Friedreich's ataxia would be needed, and fewer patients would be required if only individuals with early-onset are included. INTERPRETATION: Our findings for stage-dependent progression rates have important implications for clinicians and researchers, as they provide reliable outcome measures to monitor disease progression, and enable tailored sample size calculation to guide upcoming clinical trial designs in Friedreich's ataxia. FUNDING: European Commission, Voyager Therapeutics, and EuroAtaxia.

Adult-Onset Leukoencephalopathy With Axonal Spheroids and Pigmented Glia: Review of Clinical Manifestations as Foundations for Therapeutic Development.

A comprehensive review of published literature was conducted to elucidate the genetics, neuropathology, imaging findings, prevalence, clinical course, diagnosis/clinical evaluation, potential biomarkers, and current and proposed treatments for adult-onset leukoencephalopathy with axonal spheroids and pigmented glia (ALSP), a rare, debilitating, and life-threatening neurodegenerative disorder for which disease-modifying therapies are not currently available. Details on potential efficacy endpoints for future interventional clinical trials in patients with ALSP and data related to the burden of the disease on patients and caregivers were also reviewed. The information in this position paper lays a foundation to establish an effective clinical rationale and address the clinical gaps for creation of a robust strategy to develop therapeutic agents for ALSP, as well as design future clinical trials, that have clinically meaningful and convergent endpoints.

Defining diagnostic cutoffs in neurological patients for serum very long chain fatty acids (VLCFA) in genetically confirmed X-Adrenoleukodystrophy.

X-linked Adrenoleukodystrophy (X-ALD) is caused by mutations in the ABCD1 gene resulting in the accumulation of very long chain fatty acids (VLCFA). X-ALD is the most common peroxisomal disorder with adult patients (male and female) presenting with progressive spastic paraparesis with bladder disturbance, sensory ataxia with impaired vibration sense, and leg pain. 80% of male X-ALD patients have an adrenal failure, while adrenal dysfunction is rare in women with X-ALD. The objective of this study was to define optimal serum VLCFA cutoff values in patients with X-ALD-like phenotypes for the differentiation of genetically confirmed X-ALD and Non-X-ALD individuals. Three groups were included into this study: a) X-ALD cases with confirmed ABCD1 mutations (n = 34) and two Non-X-ALD cohorts: b) Patients with abnormal serum VCLFA levels despite negative testing for ABCD1 mutations (n = 15) resulting from a total of 1,953 VLCFA tests c) Phenotypically matching patients as Non-X-ALD controls (n = 104). Receiver operating curve analysis was used to optimize VLCFA cutoff values, which differentiate patients with genetically confirmed X-ALD and Non-X-ALD individuals. The serum concentration of C26:0 was superior to C24:0 for the detection of X-ALD. The best differentiation of Non-X-ALD and X-ALD individuals was obtained with a cutoff value of < 1.0 for the C24:0/C22:0 ratio resulting in a sensitivity of 97%, a specificity of 94.1% and a positive predictive value (PPV) of 83.8% for true X-ALD. Our findings further suggested a cutoff of < 0.02 for the ratio C26:0/C22:0 leading to a sensitivity of 90.9%, a specificity of 95.0%, and a PPV of 80.6%. Pearson correlation indicated a significant positive association between total blood cholesterol and VLCFA values. Usage of serum VLCFA are economical and established biomarkers suitable for the guidance of genetic testing matching the X-ALD phenotype. We suggest using our new optimized cutoff values, especially the two ratios (C24:0/C22:0 and C26:0/C22:0), in combination with standard lipid profiles.

Mitochondrial Morphology, Function and Homeostasis Are Impaired by Expression of an N-terminal Calpain Cleavage Fragment of Ataxin-3.

Alterations in mitochondrial morphology and function have been linked to neurodegenerative diseases, including Parkinson disease, Alzheimer disease and Huntington disease. Metabolic defects, resulting from dysfunctional mitochondria, have been reported in patients and respective animal models of all those diseases. Spinocerebellar Ataxia Type 3 (SCA3), another neurodegenerative disorder, also presents with metabolic defects and loss of body weight in early disease stages although the possible role of mitochondrial dysfunction in SCA3 pathology is still to be determined. Interestingly, the SCA3 disease protein ataxin-3, which is predominantly localized in cytoplasm and nucleus, has also been associated with mitochondria in both its mutant and wildtype form. This observation provides an interesting link to a potential mitochondrial involvement of mutant ataxin-3 in SCA3 pathogenesis. Furthermore, proteolytic cleavage of ataxin-3 has been shown to produce toxic fragments and even overexpression of artificially truncated forms of ataxin-3 resulted in mitochondria deficits. Therefore, we analyzed the repercussions of expressing a naturally occurring N-terminal cleavage fragment of ataxin-3 and the influence of an endogenous expression of the S256 cleavage fragment in vitro and in vivo. In our study, expression of a fragment derived from calpain cleavage induced mitochondrial fragmentation and cristae alterations leading to a significantly decreased capacity of mitochondrial respiration and contributing to an increased susceptibility to apoptosis. Furthermore, analyzing mitophagy revealed activation of autophagy in the early pathogenesis with reduced lysosomal activity. In conclusion, our findings indicate that cleavage of ataxin-3 by calpains results in fragments which interfere with mitochondrial function and mitochondrial degradation processes.

Serum neurofilament light is increased in multiple system atrophy of cerebellar type and in repeat-expansion spinocerebellar ataxias: a pilot study.

Blood biomarkers in degenerative ataxias are still largely missing. Here, we aimed to provide piloting proof-of-concept that serum Neurofilament light (NfL) could offer a promising peripheral blood biomarker in degenerative ataxias. Specifically, as a marker of neuronal damage, NfL might (1) help to differentiate multiple system atrophy of cerebellar type (MSA-C) from sporadic adult-onset ataxia (SAOA), and (2) show increases in repeat-expansion spinocerebellar ataxias (SCAs) which might be amenable to treatment in the future. To explore these two hypotheses, we measured serum NfL levels by single-molecule array (Simoa) technique in 115 subjects, comprising patients with MSA-C (n = 25), SAOA (n = 25), the most frequent repeat-expansion SCAs (SCA 1, 2, 3 and 6) (n = 20), and age-matched controls (n = 45). Compared to controls, NfL was significantly increased in MSA-C, with levels significantly higher than in SAOA (AUC = 0.74 (0.59-0.89), mean and 95% confidence interval, p = .004). NfL was also significantly increased in SCA patients as compared to controls (AUC = 0.91 (0.81-1.00), p < .001), including NfL increases in SCA1 and SCA3. These findings provide first proof-of-concept that NfL might provide a promising peripheral biomarker in degenerative ataxias, e.g. supporting the differentiation of MSA-C from SAOA, and indicating neuronal damage in repeat-expansion SCAs.

Beyond ALS and FTD: the phenotypic spectrum of TBK1 mutations includes PSP-like and cerebellar phenotypes.

Mutations in the TANK-binding kinase 1 gene (TBK1) are a rare, but recurrent cause of amyotrophic lateral sclerosis (ALS) and frontotemporal dementia (FTD). However, the complete phenotypic spectrum of syndromes associated with TBK1 mutations remains to be elucidated. Using next-generation panel-sequencing of neurodegenerative disease genes, we identified a TBK1 index patient presenting with a progressive supranuclear palsy-like syndrome. Consecutively, we screened the whole-exome sequencing data of 439 index subjects presenting with various neurodegenerative syndromes outside the ALS-FTD spectrum for TBK1 mutations. Based on this genetic screen, we identified another TBK1 index patient presenting with progressive cerebellar ataxia. Both index patients carried the established p.Glu643del TBK1 mutation (c.1928_1930delAAG). In the index patients' families, we identified mesencephalic and cerebellar atrophy as recurrent imaging findings of TBK1-associated neurodegeneration, with cerebellar atrophy occurring even in presymptomatic mutation carriers. Our findings demonstrate that the phenotypic spectrum of TBK1 mutations extends beyond ALS and FTD to include also progressive supranuclear palsy-like and cerebellar syndromes, with mesencephalon and cerebellum representing recurrent sites of TBK1-associated neurodegeneration.

A combinatorial approach to identify calpain cleavage sites in the Machado-Joseph disease protein ataxin-3.

Ataxin-3, the disease protein in Machado-Joseph disease, is known to be proteolytically modified by various enzymes including two major families of proteases, caspases and calpains. This processing results in the generation of toxic fragments of the polyglutamine-expanded protein. Although various approaches were undertaken to identify cleavage sites within ataxin-3 and to evaluate the impact of fragments on the molecular pathogenesis of Machado-Joseph disease, calpain-mediated cleavage of the disease protein and the localization of cleavage sites remained unclear. Here, we report on the first precise localization of calpain cleavage sites in ataxin-3 and on the characterization of the resulting breakdown products. After confirming the occurrence of calpain-derived fragmentation of ataxin-3 in patient-derived cell lines and post-mortem brain tissue, we combined in silico prediction tools, western blot analysis, mass spectrometry, and peptide overlay assays to identify calpain cleavage sites. We found that ataxin-3 is primarily cleaved at two sites, namely at amino acid positions D208 and S256 and mutating amino acids at both cleavage sites to tryptophan nearly abolished ataxin-3 fragmentation. Furthermore, analysis of calpain cleavage-derived fragments showed distinct aggregation propensities and toxicities of C-terminal polyglutamine-containing breakdown products. Our data elucidate the important role of ataxin-3 proteolysis in the pathogenesis of Machado-Joseph disease and further emphasize the relevance of targeting this disease pathway as a treatment strategy in neurodegenerative disorders.

Nuclear calcium signaling induces expression of the synaptic organizers Lrrtm1 and Lrrtm2.

Calcium transients in the cell nucleus evoked by synaptic activity in hippocampal neurons function as a signaling end point in synapse-to-nucleus communication. As an important regulator of neuronal gene expression, nuclear calcium is involved in the conversion of synaptic stimuli into functional and structural changes of neurons. Here we identify two synaptic organizers, Lrrtm1 and Lrrtm2, as targets of nuclear calcium signaling. Expression of both Lrrtm1 and Lrrtm2 increased in a synaptic NMDA receptor- and nuclear calcium-dependent manner in hippocampal neurons within 2-4 h after the induction of action potential bursting. Induction of Lrrtm1 and Lrrtm2 occurred independently of the need for new protein synthesis and required calcium/calmodulin-dependent protein kinases and the nuclear calcium signaling target CREB-binding protein. Analysis of reporter gene constructs revealed a functional cAMP response element in the proximal promoter of Lrrtm2, indicating that at least Lrrtm2 is regulated by the classical nuclear Ca(2+)/calmodulin-dependent protein kinase IV-CREB/CREB-binding protein pathway. These results suggest that one mechanism by which nuclear calcium signaling controls neuronal network function is by regulating the expression of Lrrtm1 and Lrrtm2.