Mitochondrial F0F1-ATP synthase governs the induction of mitochondrial fission.

Mitochondrial dynamics is a process that balances fusion and fission events, the latter providing a mechanism for segregating dysfunctional mitochondria. Fission is controlled by the mitochondrial membrane potential (ΔΨm), optic atrophy 1 (OPA1) cleavage, and DRP1 recruitment. It is thought that this process is closely linked to the activity of the mitochondrial respiratory chain (MRC). However, we report here that MRC inhibition does not decrease ΔΨm nor increase fission, as evidenced by hyperconnected mitochondria. Conversely, blocking F0F1-ATP synthase activity induces fragmentation. We show that the F0F1-ATP synthase is sensing the inhibition of MRC activity by immediately promoting its reverse mode of action to hydrolyze matrix ATP and restoring ΔΨm, thus preventing fission. While this reverse mode is expected to be inhibited by the ATPase inhibitor ATPIF1, we show that this sensing is independent of this factor. We have unraveled an unexpected role of F0F1-ATP synthase in controlling the induction of fission by sensing and maintaining ΔΨm.

Transactive response DNA-binding protein 43 is enriched at the centrosome in human cells.

The centrosome, as the main microtubule organizing centre, plays key roles in cell polarity, genome stability and ciliogenesis. The recent identification of ribosomes, RNA-binding proteins and transcripts at the centrosome suggests local protein synthesis. In this context, we hypothesized that TDP-43, a highly conserved RNA binding protein involved in the pathophysiology of amyotrophic lateral sclerosis and frontotemporal lobar degeneration, could be enriched at this organelle. Using dedicated high magnification sub-diffraction microscopy on human cells, we discovered a novel localization of TDP-43 at the centrosome during all phases of the cell cycle. These results were confirmed on purified centrosomes by western blot and immunofluorescence microscopy. In addition, the co-localization of TDP-43 and pericentrin suggested a pericentriolar enrichment of the protein, leading us to hypothesize that TDP-43 might interact with local mRNAs and proteins. Supporting this hypothesis, we found four conserved centrosomal mRNAs and 16 centrosomal proteins identified as direct TDP-43 interactors. More strikingly, all the 16 proteins are implicated in the pathophysiology of TDP-43 proteinopathies, suggesting that TDP-43 dysfunction in this organelle contributes to neurodegeneration. This first description of TDP-43 centrosomal enrichment paves the way for a more comprehensive understanding of TDP-43 physiology and pathology.

Clinical and electrophysiological characteristics of women with X-linked Charcot-Marie-Tooth disease.

BACKGROUND: X-Linked Charcot-Marie-Tooth disease type 1 (CMTX1) is characterized by gender differences in clinical severity. Women are usually clinically affected later and less severely than men. However, their clinical presentation appears to be heterogenous. Our aim was to extend the phenotypic description in a large series of women with CMTX1. METHODS: We retrospectively evaluated 263 patients with CMTX1 from 11 French reference centers. Demographic, clinical, and nerve conduction data were collected. The severity was assessed by CMT Examination Score (CMTES) and Overall Neuropathy Limitations Scale (ONLS) scores. We looked for asymmetrical strength, heterogeneous motor nerve conduction velocity (MNCV), and motor conduction blocks (CB). RESULTS: The study included 137 women and 126 men from 151 families. Women had significantly more asymmetric motor deficits and MNCV than men. Women with an age of onset after 19 years were milder. Two groups of women were identified after 48 years of age. The first group represented 55%, with women progressing as severely as men, however, with a later onset age. The second group had mild or no symptoms. Some 39% of women had motor CB. Four women received intravenous immunoglobulin before being diagnosed with CMTX1. CONCLUSIONS: We identified two subgroups of women with CMTX1 who were over 48 years of age. Additionally, we have demonstrated that women with CMTX can exhibit an atypical clinical presentation, which may result in misdiagnosis. Therefore, in women presenting with chronic neuropathy, the presence of clinical asymmetry, heterogeneous MNCV, and/or motor CB should raise suspicion for X-linked CMT, particularly CMTX1, and be included in the differential diagnosis.

Design and application of a customizable relational DataBase to assess clinicopathological correlations and concomitant pathology in neurodegenerative diseases.

The diagnosis of neurodegenerative diseases is made complex by the heterogenous phenotype of the patients and the regular occurrence of concomitant pathology. Studying clinicopathological correlations in autopsy series is a central approach to improve pathological prediction in clinical practice. However, such method requires a wealth of information, and the use of standard spreadsheet software is hardly suitable. To overcome this constraint, we designed a customizable and freely available neuropathology form with 456 data entry fields driven by an open-source DataBase Management Systems (DBMS) using Structured Query Language (SQL). This approach allowed us to optimize the compilation of clinical and pathological data from our brain collection (264 autopsied patients, 22,885 data points). Information was then easily retrieved using general and specific queries, facilitating the analysis of demographics, clinicopathological correlations, and incidental and concomitant proteinopathies. Tau, amyloid-ß and α-synuclein incidental pathology was observed in respectively 78.1%, 42.8%, and 10.7% of all the patients. These proportions increased with age, reaching 100% for Tau pathology after 80. Concomitant proteinopathy was observed in 46.4% of the patients diagnosed with neurodegenerative diseases and prion disease. We observed a particularly high rate of co-pathology in patients with Dementia with Lewy bodies (81.3% of associated Tau and amyloid-ß pathology) and Creutzfeldt-Jakob disease (68.4% of associated Tau pathology). Finally, we used specific queries to identify old cases that could meet newly defined neuropathological criteria and revised the diagnosis of a 90-year-old patient to LATE Stage 2. Increasing our understanding of clinicopathological correlations in neurodegenerative diseases is crucial given the implications in clinical diagnosis, biomarker identification and targeted therapies assessment. The precise characterization of clinical and pathological data of autopsy series remains a central approach but the large amount of generated data should encourage a more systematic use of DBMS.

Anti-disialosyl-immunoglobulin M chronic autoimmune neuropathies: a nationwide multicenter retrospective study.

BACKGROUND AND PURPOSE: In this retrospective study involving 14 university hospitals from France and Switzerland, the aim was to define the clinicopathological features of chronic neuropathies with anti-disialosyl ganglioside immunoglobulin M (IgM) antibodies (CNDA). RESULTS: Fifty-five patients with a polyneuropathy evolving for more than 2 months and with at least one anti-disialosyl ganglioside IgM antibody, that is, anti-GD1b, -GT1b, -GQ1b, -GT1a, -GD2 and -GD3, were identified. Seventy-eight percent of patients were male, mean age at disease onset was 55 years (30-76) and disease onset was progressive (82%) or acute (18%). Patients presented with limb sensory symptoms (94% of cases), sensory ataxia (85%), oculomotor weakness (36%), limb motor symptoms (31%) and bulbar muscle weakness (18%). Sixty-five percent of patients had a demyelinating polyradiculoneuropathy electrodiagnostic profile and 24% a sensory neuronopathy profile. Anti-GD1b antibodies were found in 78% of cases, whilst other anti-disialosyl antibodies were each observed in less than 51% of patients. Other features included nerve biopsy demyelination (100% of cases), increased cerebrospinal fluid protein content (75%), IgM paraprotein (50%) and malignant hemopathy (8%). Eighty-six percent of CNDA patients were intravenous immunoglobulins-responsive, and rituximab was successfully used as second-line treatment in 50% of cases. Fifteen percent of patients had mild symptoms and were not treated. CNDA course was progressive (55%) or relapsing (45%), and 93% of patients still walked after a mean disease duration of 11 years. CONCLUSION: Chronic neuropathies with anti-disialosyl ganglioside IgM antibodies have a recognizable phenotype, are mostly intravenous immunoglobulins-responsive and present with a good outcome in a majority of cases.

InFUSing antisense oligonucleotides for treating ALS.

The question of a loss or toxic gain of function in FUS-related amyotrophic lateral sclerosis is still debated. Recently, Korobeynikov et al. argued that FUS mutations lead to a gain of function and showed that lowering wild-type and mutant FUS levels could be a promising therapeutic strategy.

Towards personalized medicine for amyotrophic lateral sclerosis.

Mohassel et al. provide unprecedented dichotomy of consequences on sphingolipid biosynthesis between pathogenic variants in the SPTLC1 gene, responsible for either amyotrophic lateral sclerosis (ALS) or hereditary sensory and autonomic neuropathy type 1 (HSAN1). Normalization of sphingolipid levels by siRNA selectively targeting the ALS mutant allele mRNA sheds light on new therapeutic approaches.

Genotype-phenotype correlation in French patients with myelin protein zero gene-related inherited neuropathy.

BACKGROUND AND PURPOSE: Preparations for clinical trials of unfolded protein response (UPR) inhibitors (such as Sephin1) that target the upregulated UPR in patients with Charcot-Marie-Tooth disease (CMT) carrying MPZ mutations are currently underway. The inclusion criteria for these trials are still being formulated. Our objective was to characterize the relation between genotypes and phenotypes in patients with CMT caused by MPZ mutations, and to refine the inclusion criteria for future trials. METHODS: Clinical and neurophysiological data of CMT patients with MPZ mutations were retrospectively collected at 11 French reference centers. RESULTS: Forty-four mutations in MPZ were identified in 91 patients from 61 families. There was considerable heterogeneity. The same mutation was found to cause either axonal or demyelinating neuropathy. Three groups were identified according to the age at disease onset. CMT Examination Score (CMTES) tended to be higher in the early (≤22 years) and adult (23-47 years) onset groups (mean CMTESv2 = 10.4 and 10.0, respectively) than in the late onset group (>47 years, mean CMTESv2 = 8.6, p = 0.47). There was a significant positive correlation between CMTESv2 and the age of patients in Groups I (p = 0.027) and II (p = 0.023), indicating that clinical severity progressed with age in these patients. CONCLUSIONS: To optimize the selection of CMT patients carrying MPZ mutations for the upcoming trials, inclusion criteria should take into account the pathophysiology of the disease (upregulated UPR). Recruited patients should have a mild to moderate disease severity and a disease onset at between 18 and 50 years, as these patients exhibit significant disease progression over time.

Improved detection of mitochondrial DNA instability in mitochondrial genome maintenance disorders.

PURPOSE: Diseases caused by defects in mitochondrial DNA (mtDNA) maintenance machinery, leading to mtDNA deletions, form a specific group of disorders. However, mtDNA deletions also appear during aging, interfering with those resulting from mitochondrial disorders. METHODS: Here, using next-generation sequencing (NGS) data processed by eKLIPse and data mining, we established criteria distinguishing age-related mtDNA rearrangements from those due to mtDNA maintenance defects. MtDNA deletion profiles from muscle and urine patient samples carrying pathogenic variants in nuclear genes involved in mtDNA maintenance (n = 40) were compared with age-matched controls (n = 90). Seventeen additional patient samples were used to validate the data mining model. RESULTS: Overall, deletion number, heteroplasmy level, deletion locations, and the presence of repeats at deletion breakpoints were significantly different between patients and controls, especially in muscle samples. The deletion number was significantly relevant in adults, while breakpoint repeat lengths surrounding deletions were discriminant in young subjects. CONCLUSION: Altogether, eKLIPse analysis is a powerful tool for measuring the accumulation of mtDNA deletions between patients of different ages, as well as in prioritizing novel variants in genes involved in mtDNA stability.

Antibodies to the Caspr1/contactin-1 complex in chronic inflammatory demyelinating polyradiculoneuropathy.

Previous studies have described the clinical, serological and pathological features of patients with chronic inflammatory demyelinating polyradiculoneuropathy (CIDP) and antibodies directed against the paranodal proteins neurofascin-155, contactin-1 (CNTN1), contactin-associated protein-1 (Caspr1), or nodal forms of neurofascin. Such antibodies are useful for diagnosis and potentially treatment selection. However, antibodies targeting Caspr1 only or the Caspr1/CNTN1 complex have been reported in few patients with CIDP. Moreover, it is unclear if these patients belong to the same pathophysiological subgroup. Using cell-based assays in routine clinical testing, we identified sera from patients with CIDP showing strong membrane reactivity when both CNTN1 and Caspr1 were co-transfected (but not when CNTN1 was transfected alone). Fifteen patients (10 male; aged between 40 and 75) with antibodies targeting Caspr1/CNTN1 co-transfected cells were enrolled for characterization. The prevalence of anti-Caspr1/CNTN1 antibodies was 1.9% (1/52) in the Sant Pau CIDP cohort, and 4.3% (1/23) in a German cohort of acute-onset CIDP. All patients fulfilled European Federation of Neurological Societies/Peripheral Nerve Society (EFNS/PNS) definite diagnostic criteria for CIDP. Seven (47%) were initially diagnosed with Guillain-Barré syndrome due to an acute-subacute onset. Six (40%) patients had cranial nerve involvement, eight (53%) reported neuropathic pain and 12 (80%) ataxia. Axonal involvement and acute denervation were frequent in electrophysiological studies. Complete response to intravenous immunoglobulin was not observed, while most (90%) responded well to rituximab. Enzyme-linked immunosorbent assay (ELISA) and teased nerve fibre immunohistochemistry confirmed reactivity against the paranodal Caspr1/CNTN1 complex. Weaker reactivity against Caspr1 transfected alone was also detected in 10/15 (67%). Sera from 13 of these patients were available for testing by ELISA. All 13 samples reacted against Caspr1 by ELISA and this reactivity was enhanced when CNTN1 was added to the Caspr1 ELISA. IgG subclasses were also investigated by ELISA. IgG4 was the predominant subclass in 10 patients, while IgG3 was predominant in other three patients. In conclusion, patients with antibodies to the Caspr1/CNTN1 complex display similar serological and clinical features and constitute a single subgroup within the CIDP syndrome. These antibodies likely target Caspr1 primarily and are detected with Caspr1-only ELISA, but reactivity is optimal when CNTN1 is added to Caspr1 in cell-based assays and ELISA.

Late-onset camptocormia caused by a heterozygous in-frame CAPN3 deletion.

Camptocormia is defined by a pathological involuntary flexion of the thoracic and lumbar spine that is fully reducible in the supine position. Although originally described as a manifestation of conversion disorder, it is more commonly caused by a wide range of neurological diseases, in particular movement and neuromuscular disorders. We describe here a rare case of late onset camptocormia caused by autosomal dominant calpainopathy due to a heterozygous in-frame deletion in CAPN3 leading to loss of a single lysin amino acid in the catalytic domain of calpain-3. Creatine kinase levels, electromyography, and thigh muscle MRI were normal. Muscle biopsy did not show lobulated fibers and calpain-3 protein expression was not decreased, but in vitro functional assays showed impaired proteolytic function of. Lys254del CAPN3. Autosomal dominant calpainopathy should be considered in the differential diagnosis of late onset camptocormia and unexplained paravertebral myopathies even in presence of normal creatine kinase levels, and in absence of lobulated fibers, of decreased calpain-3 protein expression, and of muscle limb involvement.

NeuroQ: A neurophobia screening tool assesses how roleplay challenges neurophobia.

BACKGROUND: Neurophobia is a chronic disease of medical students and junior doctors. Early detection is needed to facilitate prevention and management as this fear can negatively impact patient care. METHODS: We conducted a two-part mono-centric study at the faculty of Medicine, Sorbonne University, in Paris. Part one: a cross-sectional study to validate a newly constructed neurophobia scale, NeuroQ. Part two: a prospective longitudinal study to assess the impact of The Move on student neurophobia using NeuroQ. A population-based sample of second-year medical students of the 2019 and 2020 class of the Faculty of Medicine of Sorbonne University were invited to participate. RESULTS: NeuroQ incorporates the main themes of the neurophobia definition and demonstrates uni-dimensionality. Three hundred and ninety-five medical students participated in the study (mean age was 20.0 years, SD: 2.1 years) assessing the effect of The Move teaching on neurophobia. Two hundred and eighty-eight (72.9%) students were female. After the Move teaching the mean NeuroQ score was significantly lower compared to the baseline NeuroQ score (mean [SD] variation, -1.1 [2.6], p < 0.001). There was a 22.3% relative reduction in the number of neurophobic students after The Move teaching. CONCLUSION: Our results highlight the utility of NeuroQ in assessing (i) baseline neurophobia and (ii) the impact of pre-clinical educational interventions on neurophobia. Furthermore, we have shown the importance of pre-clinical educational interventions, such as The Move, in tackling neurophobia.

Effect of familial clustering in the genetic screening of 235 French ALS families.

OBJECTIVES: To determine whether the familial clustering of amyotrophic lateral sclerosis (ALS) cases and the phenotype of the disease may help identify the pathogenic genes involved. METHODS: We conducted a targeted next-generation sequencing analysis on 235 French familial ALS (FALS), unrelated probands to identify mutations in 30 genes linked to the disease. The genealogy, that is, number of cases and generations with ALS, gender, age, site of onset and the duration of the disease were analysed. RESULTS: Regarding the number of generations, 49 pedigrees had only one affected generation, 152 had two affected generations and 34 had at least three affected generations. Among the 149 pedigrees (63.4%) for which a deleterious variant was found, an abnormal G4C2 expansion in C9orf72 was found in 98 cases as well as SOD1, TARBP or FUS mutations in 30, 9 and 7 cases, respectively. Considering pedigrees from the number of generations, abnormal G4C2 expansion in C9orf72 was more frequent in pedigrees with pairs of affected ALS cases, which represented 65.2% of our cohort. SOD1 mutation involved all types of pedigrees. No TARDBP nor FUS mutation was present in monogenerational pedigrees. TARDBP mutation predominated in bigenerational pedigrees with at least three cases and FUS mutation in multigenerational pedigrees with more than seven cases, on average, and with an age of onset younger than 45 years. CONCLUSION: Our results suggest that familial clustering, phenotypes and genotypes are interconnected in FALS, and thus it might be possible to target the genetic screening from the familial architecture and the phenotype of ALS cases.

Turning up the Green Light.

Fluorescent proteins (FPs) have become indispensable tools in biological research for labeling cells and proteins and sensing their biochemical activity. By introducing 'folding mutations', Campbell et al. engineered a new GFP variant with dramatically enhanced cellular brightness and stability, facilitating advanced cellular bioimaging applications in neuroscience and beyond.

Engineered Microbes for Producing Anticholinergics.

The tropane alkaloids (TAs) hyoscyamine and scopolamine function as acetylcholine receptor antagonists and are used clinically as parasympatholytics to treat neuromuscular disorders in humans. While TAs are synthesized in a small subset of plant families, these specialized metabolites are only accumulated in limited quantities in plant organs. The complex chemical structures of these compounds make their industrial production by chemical synthesis very challenging, Therefore, the supply of these TAs still relies on intensive farming of Duboisia shrubs in tropical countries. Many adverse factors such as climate fluctuations and pandemics can thus influence annual world production. Based on the landmark microbial production of the antimalarial semi-synthetic artemisinin, the Smolke group recently developed a yeast cell factory capable of de novo synthesizing hyoscyamine and scopolamine, thus paving the way for an alternative production of these compounds.

Differences in clinical features between small fiber and sensitive large fiber neuropathies in Sjögren's syndrome.

BACKGROUND: To distinguish large (LFN) and small fiber neuropathies (SFN) in Sjögren's syndrome (SS) requires electroneuromyography (EMG) first, but this is time-consuming and has sometimes a limited accessibility, which can lead to a diagnostic delay. We aimed to identify clinical features that could distinguish SFN from sensitive LFN in SS. METHODS: The study included patients with SS who were monitored in the internal medicine and neurology departments at Angers University Hospital between 2010 and 2016, and who were tested for suspected peripheral neuropathy. Patients with clinical motor involvement were excluded. LFN diagnosis was based on EMG. SFN diagnosis was based on intraepidermal nerve fiber density on skin biopsies in patients with no abnormality on EMG. RESULTS: LFN and SFN were diagnosed respectively in 22 (6.9%) and 17 (5.4%) patients among 317 patients with SS. Prevalence of anti-SSA antibodies was lower in the SFN group compared to the LFN group (p=0.002). The types of paresthesia did not differ between the 2 groups. After adjustment for age and sex, SFN was associated with dysautonomia (p=0.01, OR 8.4 [CI 95%: 1.7-42.4]) and without length-dependent topography (p=0.03, OR 0.2 [0.04-0.8] in comparison with the LFN group. CONCLUSIONS: An association of non-length-dependent pattern and dysautonomia seems to predict the absence of LFN in SS and encourages the search for SFN. In contrary, patients with length-dependent involvement and without dysautonomia should be prioritized for EMG.

Strength of the Association of Elevated Vitamin B12 and Solid Cancers: An Adjusted Case-Control Study.

The association between elevated plasma vitamin B12 (B12) level and solid cancers has been documented by two national registries. However, their design did not allow for the adjustment for other conditions associated with elevated B12. The objectives of this study were to confirm this association after the adjustment for all causes of elevated B12, and to study the variations according to the increasing B12 level, the type of cancers, and the presence of metastases. We compared 785 patients with B12 ≥ 1000 ng/L with 785 controls matched for sex and age with B12 < 1000 ng/L. Analyses were adjusted for the causes of elevated B12: myeloid blood malignancies, acute or chronic liver diseases, chronic kidney failure, autoimmune or inflammatory diseases, and excessive B12 supplementation. A B12 ≥ 1000 ng/L was associated with the presence of solid cancer without metastases (OR 1.96 [95%CI: 1.18 to 3.25]) and with metastases (OR 4.21 [95%CI: 2.67 to 6.64]) after adjustment for all elevated B12-related causes. The strength of the association rose with the increasing B12 level, in particular in cases of metastases. No association between liver cancers and elevated B12 level was found after adjustment for chronic liver diseases. In conclusion, unexplained elevated B12 levels should be examined as a possible marker of solid cancer.

Oxidative stress contributes differentially to the pathophysiology of Charcot-Marie-Tooth disease type 2K.

Charcot-Marie-Tooth (CMT) disease is a common inherited peripheral neuropathy. The CMT2K axonal form is associated with GDAP1 dominant mutations, which according to the affected domain cause a gradient of severity. Indeed, the p.C240Y mutation, located within GDAP1 glutathione S-transferase (GST) domain and associated to a mitochondrial complex I defect, is related to a faster disease progression, compared to other mutations, such as the p.R120W located outside the GST domain. Here, we analysed the pathophysiology of six CMT2K fibroblast cell lines, carrying either the p.C240Y or p.R120W mutations. We show that complex I deficiency leads to a redox potential alteration and a significant reduction of sirtuin 1 (SIRT1) expression, a major deacetylase sensitive to the cellular redox state, and NRF1 the downstream target of SIRT1. In addition, we disclosed that the p.C240Y mutation is associated with a greater mitochondrial oxidative stress than the p.R120W mutation. Moreover, complex I activity is further restored in CMT2K mutant cell lines exposed to resveratrol. Together, these results suggest that the reduction of oxidative stress may constitute a promising therapeutic strategy for CMT2K.

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.