Franck Letournel

G51D α‐synuclein mutation causes a novel Parkinsonian–pyramidal syndrome

To date, 3 rare missense mutations in the SNCA (α‐synuclein) gene and the more frequent duplications or triplications of the wild‐type gene are known to cause a broad array of clinical and pathological symptoms in familial Parkinson disease (PD). Here, we describe a French family with a parkinsonian–pyramidal syndrome harboring a novel heterozygous SNCA mutation.

Mitochondrial complex I deficiency in GDAP1-related autosomal dominant Charcot-Marie-Tooth disease (CMT2K)

Mutations in GDAP1, an outer mitochondrial membrane protein responsible for recessive Charcot-Marie-Tooth disease (CMT4A), have also been associated with CMT2K, a dominant form of the disease. The three CMT2K patients we studied carried a novel dominant GDAP1 mutation, C240Y (c.719G > A). Mitochondrial respiratory chain complex I activity in fibroblasts from CMT2K patients was 40% lower than in controls, whereas the tubular mitochondria were 33% larger in diameter and the mitochondrial mass was 20% greater. Thus, besides the regulatory role GDAP1 plays in mitochondrial network dynamics, it may also be involved in energy production and in the control of mitochondrial volume.

Photo-responsive polymer with erasable and reconfigurable micro- and nano-patterns: An in vitro study for neuron guidance

The interaction of cells with nanoscale topography has proven to be an important modality in controlling cell responses. Topographic parameters on material surfaces play a role in cell growth. We have synthesized a new bio compatible polymer containing photoswitching molecules. Stripepatterned (groove/ridge pattern) were patterned and erased with ease on this bio azopolymer with two different set-ups: one with the projection of an optical interference pattern and the other one by molecular self-organization with one single laser beam. These two set-ups allow the re-writing of pattern after erasing and its inscription in vitro. PC12 cells were cultured on the bio-photoswitching patterned polymer and compared with PC12 cells growing on a well know substrate: poly-L-lysine. This result is of interest for facilitating contact guidance and designing reconfigurable scaffold for neural network formation in vitro.

Mycolactone gene expression is controlled by strong SigA-like promoters with utility in studies of Mycobacterium ulcerans and Buruli ulcer.

Mycolactone A/B is a lipophilic macrocyclic polyketide that is the primary virulence factor produced by Mycobacterium ulcerans, a human pathogen and the causative agent of Buruli ulcer. In M. ulcerans strain Agy99 the mycolactone polyketide synthase (PKS) locus spans a 120 kb region of a 174 kb megaplasmid. Here we have identified promoter regions of this PKS locus using GFP reporter assays, in silico analysis, primer extension, and site-directed mutagenesis. Transcription of the large PKS genes mlsA1 (51 kb), mlsA2 (7 kb) and mlsB (42 kb) is driven by a novel and powerful SigA-like promoter sequence situated 533 bp upstream of both the mlsA1 and mlsB initiation codons, which is also functional in Escherichia coli, Mycobacterium smegmatis and Mycobacterium marinum. Promoter regions were also identified upstream of the putative mycolactone accessory genes mup045 and mup053. We transformed M. ulcerans with a GFP-reporter plasmid under the control of the mls promoter to produce a highly green-fluorescent bacterium. The strain remained virulent, producing both GFP and mycolactone and causing ulcerative disease in mice. Mosquitoes have been proposed as a potential vector of M. ulcerans so we utilized M. ulcerans-GFP in microcosm feeding experiments with captured mosquito larvae. M. ulcerans-GFP accumulated within the mouth and midgut of the insect over four instars, whereas the closely related, non-mycolactone-producing species M. marinum harbouring the same GFP reporter system did not. This is the first report to identify M. ulcerans toxin gene promoters, and we have used our findings to develop M. ulcerans-GFP, a strain in which fluorescence and toxin gene expression are linked, thus providing a tool for studying Buruli ulcer pathogenesis and potential transmission to humans.

Neuropathie démyélinisante au cours d’un traitement par anti-TNF alpha et revue de la littérature

Resume Introduction Les anti-TNF alpha, utilises de facon croissante dans des affections comme la polyarthrite rhumatoide, sont parfois responsables d’atteintes demyelinisantes du systeme nerveux central. Des cas d’atteintes du systeme nerveux peripherique commencent a etre rapportes. Observation Une femme de 39 ans a developpe une neuropathie demyelinisante chronique apres introduction d’un traitement par Adalimumab (Humira ® ). Les traitements par corticoide puis par immunoglobulines intraveineuses se sont reveles inefficaces. L’evolution a ete progressivement favorable six mois apres l’arret de l’Humira ® . Discussion Plusieurs observations recentes rapportent des neuropathies, le plus souvent demyelinisantes, lors de traitements par anti-TNF alpha. Conclusion Une vigilance particuliere concernant l’apparition de signes evocateurs d’atteinte du systeme nerveux peripherique est souhaitable lors de l’utilisation des anti-TNF alpha et l’existence d’une neuropathie pourrait constituer une contre indication a l’utilisation de ces produits.

Diagnostic value of minor salivary glands biopsy for the detection of Lewy pathology.

The recent demonstration of the presence of Lewy pathology in the submandibular glands of Parkinsons disease (PD) patients prompted us to evaluate the diagnostic performance of minor salivary gland biopsy for PD. Minor salivary glands were examined for Lewy pathology using phosphorylated alpha-synuclein antibody in 16 patients with clinically diagnosed PD and 11 control subjects with other neurological disorders. Abnormal accumulation of alpha-synuclein was found in 3 out of 16 PD patients. Two control subjects exhibited weak phosphorylated alpha-synuclein immunoreactivity. Our results do not support the use of minor salivary glands biopsy for the detection of Lewy pathology in living subjects.

Ethambutol-induced optic neuropathy linked to OPA1 mutation and mitochondrial toxicity.

Ethambutol (EMB), widely used in the treatment of tuberculosis, has been reported to cause Lebers hereditary optic neuropathy in patients carrying mitochondrial DNA mutations. We study the effect of EMB on mitochondrial metabolism in fibroblasts from controls and from a man carrying an OPA1 mutation, in whom the drug induced the development of autosomal dominant optic atrophy (ADOA). EMB produced a mitochondrial coupling defect together with a 25% reduction in complex IV activity. EMB induced the formation of vacuoles associated with decreased mitochondrial membrane potential and increased fragmentation of the mitochondrial network. Mitochondrial genetic variations may therefore be predisposing factors in EMB-induced ocular injury.

RISK and SAFE Signaling Pathway Involvement in Apolipoprotein A-I-Induced Cardioprotection

Recent findings indicate that apolipoprotein A-I (ApoA-I) may be a protective humoral mediator involved in remote ischemic preconditioning (RIPC). This study sought to determine if ApoA-I mediates its protective effects via the RISK and SAFE signaling pathways implicated in RIPC. Wistar rats were allocated to one of the following groups. Control: rats were subjected to myocardial ischemia/reperfusion (I/R) without any further intervention; RIPC: four cycles of limb I/R were applied prior to myocardial ischemia; ApoA-I: 10 mg/Kg of ApoA-I were intravenously injected prior to myocardial ischemia; ApoA-I + inhibitor: pharmacological inhibitors of RISK/SAFE pro-survival kinase (Akt, ERK1/2 and STAT-3) were administered prior to ApoA-I injection. Infarct size was significantly reduced in the RIPC group compared to Control. Similarly, ApoA-I injection efficiently protected the heart, recapitulating RIPC-induced cardioprotection. The ApoA-I protective effect was associated with Akt and GSK-3β phosphorylation and substantially inhibited by pretreatment with Akt and ERK1/2 inhibitors. Pretreatment with ApoA-I in a rat model of I/R recapitulates RIPC-induced cardioprotection and shares some similar molecular mechanisms with those of RIPC-involved protection of the heart.

Multicenter Assessment of Immunohistochemical Methods for Pathological Alpha-Synuclein in Sigmoid Colon of Autopsied Parkinson's Disease and Control Subjects

BACKGROUND Conflicting results from studies of Lewy-type α-synucleinopathy (LTS) in colonic biopsies of subjects with Parkinsons disease (PD) prompted a two-part multicenter assessment. The first assessment, now published (Acta Neuropathol Commun 4 : 35, 2016), examined archived colonic biopsies and found that none of the tested methods was adequately sensitive or specific. OBJECTIVE As the amount of nervous tissue in typical colonic biopsies may be insufficient, and the clinical diagnosis of PD not completely accurate, the objective of the current study was to use instead full-thickness sections of sigmoid colon from autopsy-proven PD and normal subjects. METHODS Seven different immunohistochemical (IHC) methods were used, employing five different primary antibodies and four different combinations of epitope exposure and signal development protocols. Specific staining was defined as being restricted to morphological features consistent with neuronal elements. Stained slides from each subject were independently categorized as being positive or negative for LTS, and their density semi-quantitatively graded, by four raters blinded to diagnosis. RESULTS Agreement and mean diagnostic performance varied markedly between raters. With the two most accurate raters, 5 methods achieved diagnostic accuracies of 70% or greater; one method had 100% accuracy and 100% inter-rater agreement. The submucosa had the highest prevalence of pathological LTS staining, followed by the muscularis and mucosa. CONCLUSIONS The major conclusion of this study is that, when sufficient submucosa and LTS is present, and when specific staining is defined as being consistent with neuronal morphology, adequately-trained raters may reliably distinguish PD colon from control using suitable IHC methods.

Mitochondrial DNA A3243G mutation involved in familial diabetes, chronic intestinal pseudo-obstruction and recurrent pancreatitis.

AIMS To report on a family with five members who carry the A3243G mutation in mitochondrial tRNA for leucine 1 (MTTL1) and present with diabetes, chronic intestinal pseudo-obstruction (CIPO) and recurrent pancreatitis, and to screen for this mutation in a cohort of 36 unrelated patients with recurrent pancreatitis. METHODS The mutation was quantified in several tissue samples from patients. Respiratory chain activity was studied in muscle biopsies and fibroblast cultures. In addition, the thymidine phosphorylase gene (TP) involved in mitochondrial neurogastrointestinal encephalomyopathy (MNGIE) and three genes involved in chronic pancreatitis - PRSS1, SPINK1 and CFTR - were sequenced in affected patients. Finally, the MTTL1 gene was examined in 36 unrelated patients who had recurrent pancreatitis, but no mutations in the PRSS1 and SPINK1 genes. RESULTS Heteroplasmy for the mtDNA A3243G mutation was found in all tissue samples from these patients, but no mutations were found in the genes coding for thymidine phosphorylase, PRSS1, SPINK1 and CFTR. Also, none of the 36 unrelated patients with recurrent pancreatitis were carrying any MTTL1 mutations. CONCLUSION The mtDNA A3243G mutation associated with the gastrointestinal manifestations observed in the affected family should be regarded as a possible cause of CIPO and unexplained recurrent pancreatitis. However, the mutation is probably only weakly involved in cases of isolated recurrent pancreatitis.