Guy Lenaers
Angers University, Mitochondrial Medicine Research Centre, Faculty Member
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The sequence of the large subunit ribosomal RNA (LsuRNA) gene of the dinoflagellate Prorocentrum micans has been determined. The inferred rRNA sequence [3408 nucleotides (nt)] is presented in its most probable secondary structure based on... more
The sequence of the large subunit ribosomal RNA (LsuRNA) gene of the dinoflagellate Prorocentrum micans has been determined. The inferred rRNA sequence [3408 nucleotides (nt)] is presented in its most probable secondary structure based on compensatory mutations, energy, and conservation criteria. No introns have been found but a hidden break is present in the second variable domain, 690 nt from the 5' end, as judged by agarose gel electrophoresis and primer extension experiments. Prorocentrum micans LsuRNA length and G+C content are close to those of ciliates and yeast. The conserved portions of the molecule (1900 nt) have been aligned with corresponding sequences from various eukaryotes, including five protista, one metaphyta, and three metazoa. An extensive phylogenetic study was performed, comparing two phenetic methods (neighbor joining on difference matrix, and Fitch and Margoliash on Knuc values matrix) and one cladistic (parsimony). The three methods led to similar tree topologies, except for the emergence of yeast that groups with ciliates and dinoflagellates when phenetic methods are used, but emerges later in the most parsimonious tree. This discrepancy was checked by statistical analyses on reduced trees (limited to four species) inferred using parsimony and evolutionary parsimony methods. The data support the phenetic tree topologies and a close relationship between dinoflagellates, ciliates, and yeast.
Research Interests: Evolutionary Biology, Genetics, Phylogenetics, Molecular Evolution, Biology, and 15 moreMedicine, Phylogeny, Close relationships, Animals, ribosomal RNA, Molecular phylogenetics, Secondary Structure, Phylogenetic Tree, Maximum Parsimony, Gel electrophoresis, Base Sequence, Ribosomal DNA, Nucleotides, Biochemistry and cell biology, and Molecular Sequence Data
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Purpose: Wolfram syndrome is an early onset genetic disease (1/160,000) featuring diabetes mellitus and optic neuropathy, associated to mutation in the WFS1 gene. Mouse model with deleted exon 8 of Wolframin shows pancreatic beta cell... more
Purpose: Wolfram syndrome is an early onset genetic disease (1/160,000) featuring diabetes mellitus and optic neuropathy, associated to mutation in the WFS1 gene. Mouse model with deleted exon 8 of Wolframin shows pancreatic beta cell atrophy, but its visual performance has not been investigated, prompting us to study its visual function and the histopathology of the retina and optic nerve. Methods: Electroretinogram (ERG, retinal function) and visual evoked potentials (VEPs, visual pathway) were performed in Wfs1-/- and Wfs1+/+ mice at 3, 6 and 9 months of age. Fundi were pictured with Micron III apparatus. Retinal ganglion cell (RGC) proportion was determined from Brn3a immuno-labeling of retinal sections. RGC axonal loss was quantified by electron microscopy in transversal optic nerve sections. Results: ERG showed a sex-dependent alteration in Wfs1 mutant mice at 3 months. Photoreceptor response amplitude (a-wave) was increased by 25.5% by Wfs1 mutation in females, while reduced by 28.2% in males. In contrast, positive scotopic threshold responses (pSTR) at the same age were found increased in mutant group by 20.5%. A preliminary study of 7 months male samples showed a severe loss of RGC somas (-50%) and axons in retina and optic nerve respectively. Finally, 7-8 months knocked-in mice presented a severe ocular hypertension. Conclusions: Electrophysiological phenotyping of Wfs1 deleted mouse exon 8 visual function indicate a significant loss of RGC in mutant mouse at 7 month. Structural analysis of retinal ganglion cell somas and axons are conducted to characterize optic neuropathy in these animals.
Research Interests: Biology, Medicine, Optic Nerve, Erg, Retina, and 4 moreRetinal, Atrophy, Optic Neuropathy, and wolfram syndrome
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Hereditary optic neuropathies are caused by the degeneration of retinal ganglion cells whose axons form the optic nerves, with a consistent genetic heterogeneity. As part of our diagnostic activity, we retrospectively evaluated the... more
Hereditary optic neuropathies are caused by the degeneration of retinal ganglion cells whose axons form the optic nerves, with a consistent genetic heterogeneity. As part of our diagnostic activity, we retrospectively evaluated the combination of Leber hereditary optic neuropathy mutations testing with the exon sequencing of 87 nuclear genes on 2186 patients referred for suspected hereditary optic neuropathies. The positive diagnosis rate in individuals referred for Leber hereditary optic neuropathy testing was 18% (199/1126 index cases), with 92% (184/199) carrying one of the three main pathogenic variants of mitochondrial DNA (m.11778G>A, 66.5%; m.3460G>A, 15% and m.14484T>C, 11%). The positive diagnosis rate in individuals referred for autosomal dominant or recessive optic neuropathies was 27% (451/1680 index cases), with 10 genes accounting together for 96% of this cohort. This represents an overall positive diagnostic rate of 30%. The identified top 10 nuclear genes included OPA1, WFS1, ACO2, SPG7, MFN2, AFG3L2, RTN4IP1, TMEM126A, NR2F1 and FDXR. Eleven additional genes, each accounting for less than 1% of cases, were identified in 17 individuals. Our results show that 10 major genes account for more than 96% of the cases diagnosed with our nuclear gene panel.
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Purpose Progressive inherited retinal dystrophies, characterized by degeneration of rod photoreceptors and then cone photoreceptors, are known as retinitis pigmentosa (RP), for which 89 genes have been identified. Today, only five... more
Purpose Progressive inherited retinal dystrophies, characterized by degeneration of rod photoreceptors and then cone photoreceptors, are known as retinitis pigmentosa (RP), for which 89 genes have been identified. Today, only five Moroccan families with RP with a genetic diagnosis have been reported, justifying our investment in providing further clinical and genetic investigations of families with RP in Morocco. Methods The clinical diagnosis based on a combination of a history of night blindness, abnormal rod or rod-cone responses in electroretinography (ERG), and constricted visual field or difficulty perceiving side objects identified three Moroccan families with an RP phenotype. Probands of these families underwent whole exome sequencing (WES), and candidate variants were evaluated for their segregation within family members. Results All patients had a history of night blindness and unrecordable rod and cone ERG traces. In addition, one patient had cystoid macular edema, and an...
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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... more
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.
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All‐trans‐retinal (atRAL) is a highly reactive carbonyl specie, known for its reactivity on cellular phosphatidylethanolamine in photoreceptor. It is generated by photoisomerization of 11‐cis‐retinal chromophore linked to opsin by the... more
All‐trans‐retinal (atRAL) is a highly reactive carbonyl specie, known for its reactivity on cellular phosphatidylethanolamine in photoreceptor. It is generated by photoisomerization of 11‐cis‐retinal chromophore linked to opsin by the Schiff's base reaction. In ABCA4‐associated autosomal recessive Stargardt macular dystrophy, atRAL results in carbonyl and oxidative stress, which leads to bisretinoid A2E, accumulation in the retinal pigment epithelium (RPE). This A2E‐accumulation presents as lipofuscin fluorescent pigment, and its photooxidation causes subsequent damage. Here we describe protection against a lethal dose of atRAL in both photoreceptors and RPE in primary cultures by a lipidic polyphenol derivative, an isopropyl‐phloroglucinol linked to DHA, referred to as IP‐DHA. Next, we addressed the cellular and molecular defence mechanisms in commonly used human ARPE‐19 cells. We determined that both polyunsaturated fatty acid and isopropyl substituents bond to phloroglucinol ...
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SummaryInherited Optic Neuropathies are blinding diseases related to mitochondrial dysfunctions jeopardizing retinal ganglion cell (RGC) survival. There are two main forms: the Leber Hereditary Optic Neuropathy (LHON) related to mutations... more
SummaryInherited Optic Neuropathies are blinding diseases related to mitochondrial dysfunctions jeopardizing retinal ganglion cell (RGC) survival. There are two main forms: the Leber Hereditary Optic Neuropathy (LHON) related to mutations in the mitochondrial genome, and the Kjer dominant optic atrophy (DOA) related to mutations in nuclear genes.Since the initial discovery of the OPA1 gene in 2000 as the major gene causing DOA, the use of WES and re‐sequencing chips disclosed many novel genes responsible for DOA. Interestingly, most of them are involved in mitochondrial dynamics, suggesting that the equilibrium between fission and fusion is crucial for RGC physiology. In this respect, using fluorescence and electron microscopy, we showed that the structure of mitochondria is drastically different according to the myelination status of RGC axons, possibly correlating anterograde and retrograde mitochondrial transport to mitochondrial dynamics. Further metabolomics analysis of an Opa1...
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Research Interests: Biology, Metabolomics, Mitochondria, DNA damage, Medicine, and 12 moreOptical Imaging, Biological Sciences, Mitochondrial DNA, Humans, Mitochondrial Dynamics, RNA-binding proteins, HeLa cells, Oxidative phosphorylation, Oxidation-Reduction, Adenosine Triphosphate, Mitochondrion, and Medical and Health Sciences
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Background: Defects in mitochondrial dynamics have been associated with various disorders, including cardiovascular diseases. OPA1 is essential for mitochondrial inner membrane fusion and mutation in OPA1 is associated with autosomal... more
Background: Defects in mitochondrial dynamics have been associated with various disorders, including cardiovascular diseases. OPA1 is essential for mitochondrial inner membrane fusion and mutation in OPA1 is associated with autosomal dominant optic atrophy. Since OPA1 has been reported to be associated with cell apoptosis, cell proliferation, mitochondrial ATP synthesis, calcium homeostasis and reactive oxygen species (ROS) production, we investigated its role in vascular function and/or structure in physiological and pathological condition like hypertension. Methods and Results: We used the heterozygous Opa1 mouse model carrying the recurrent Opa1 delTTAG mutation and OPA1 silencing in artery smooth muscle and endothelial cells. Electron microscopy revealed altered mitochondrial cristae structure in vascular smooth muscle cells and endothelial cells of Opa1+/- mice, 6 month-old Opa1+/- mice had a normal baseline blood pressure and vascular function (contraction and dilation). A chronic treatment with L-NAME induced hypertension in mice. Systolic blood pressure was significantly greater in Opa1+/- than in wild type (WT) mice. This was associated with a stronger reduction in endothelium-dependent relaxation to acetylcholine of resistance arteries in Opa1+/- than in WT animal. On the other hand, hypertension-induced wall hypertrophy in the aorta was absent in Opa1+/- in association with reduced proliferation and increased apoptosis of vascular cells. Conclusions: Thus mitochondria alteration due to OPA1 down-regulation did not affect baseline blood pressure and vascular tone but induced an excessive elevation in blood pressure in hypertension. These results suggest for the first time that OPA1 may play an important role in protection of the vasculature in pathological conditions such as hypertension.
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ABSTRACT
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Interpretation of variants of uncertain significance is an actual major challenge. We addressed this question on a set of OPA1 missense variants responsible for variable severity of neurological impairments. We used targeted metabolomics... more
Interpretation of variants of uncertain significance is an actual major challenge. We addressed this question on a set of OPA1 missense variants responsible for variable severity of neurological impairments. We used targeted metabolomics to explore the different signatures of OPA1 variants expressed in Opa1 deleted mouse embryonic fibroblasts (Opa1−/− MEFs), grown under selective conditions. Multivariate analyses of data discriminated Opa1+/+ from Opa1−/− MEFs metabolic signatures and classified OPA1 variants according to their in vitro severity. Indeed, the mild p.I382M hypomorphic variant was segregating close to the wild-type allele, while the most severe p.R445H variant was close to Opa1−/− MEFs, and the p.D603H and p.G439V alleles, responsible for isolated and syndromic presentations, respectively, were intermediary between the p.I382M and the p.R445H variants. The most discriminant metabolic features were hydroxyproline, the spermine/spermidine ratio, amino acid pool and sever...
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Research Interests: Biology, Medicine, Humans, Mutation, Male, and 6 moreClinical Sciences, Adult, Annals, Optic Neuropathy, Neurosciences, and Exon
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<p>The TDC and TLBc functional domains are represented on the TBC1D24 protein structure. The amino-acid changes identified in this work (in bold) and the published recessive and dominant mutations responsible for NHSL are shown on... more
<p>The TDC and TLBc functional domains are represented on the TBC1D24 protein structure. The amino-acid changes identified in this work (in bold) and the published recessive and dominant mutations responsible for NHSL are shown on the top, while mutations responsible for DOORS syndrome, familial infantile myoclonic epilepsy, progressive myoclonus epilepsy and early-infantile epileptic encephalopathy-16 are shown below the protein structure.</p
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Research Interests: Chemistry, Biology, Scanning Electron Microscopy, Cell Biology, Transmission Electron Microscopy, and 12 moreMitochondria, Biological Chemistry, Apoptosis, Medicine, Biological Sciences, Humans, Cytochrome C, Biological, CHEMICAL SCIENCES, Membrane Integrity, Mitochondrion, and Medical and Health Sciences
... with Mutations in the Mitochondrial Fusion Machinery Guy Lenaers, Dominique Bonneau, Cécile Delettre, Patrizia Amati-Bonneau, Emmanuelle Sarzi, Dan Miléa, Christophe Verny,Vincent Procaccio, Christian Hamel, and Pascal Reynier ...