Karyomegalic interstitial nephritis and DNA damage-induced polyploidy in fan1 nuclease-defective knock-in mice

The Fan1 endonuclease is required for repair of DNA interstrand cross-links (ICLs). Mutations in human Fan1 cause karyomegalic interstitial nephritis (KIN), but it is unclear whether defective ICL repair is responsible or whether Fan1 nuclease activity is relevant. We show that Fan1 nuclease-defective (Fan1nd/nd) mice develop a mild form of KIN. The karyomegalic nuclei from Fan1nd/nd kidneys are polyploid, and fibroblasts from Fan1nd/nd mice become polyploid upon ICL induction, suggesting that defective ICL repair causes karyomegaly. Thus, Fan1 nuclease activity promotes ICL repair in a manner that controls ploidy, a role that we show is not shared by the Fanconi anemia pathway or the Slx4–Slx1 nuclease also involved in ICL repair

Edge impact damage scenario on stiffened composite structure

Low velocity / low energy edge impact and almost-static experiments have been carried out on carbon fiber reinforced plastic (CFRP) structures. A drop-weight testing machine was used to impact four different UD laminates at 10, 20 and 35 J impact energy levels. In parallel, an almoststatic study has been conducted in order to compare its results with the impact one. Compression after impact tests will supply the residual behavior afterwards. The impact results show that the static and dynamic behaviors are different. A simplified analytical impact model is provided trying to explain the difference between static and dynamic edge impact regardless the stacking or impact energy. It actually well represents the dynamic and static initial stiffness and the crushing plateau. The fiber properties control the initial impact stiffness. In addition, regardless of the impact energy and stacking, a specific "crushing plateau" phenomenon appears. In the almost-static indentation case the properties of the matrix control the initial indentation stiffness. The experimental results will be compared to a numerical model in order to simulate the impact and compression after impact damage

Improved genome editing in human cell lines using the CRISPR method

The Cas9/CRISPR system has become a popular choice for genome editing. In this system, binding of a single guide (sg) RNA to a cognate genomic sequence enables the Cas9 nuclease to induce a double-strand break at that locus. This break is next repaired by an error-prone mechanism, leading to mutation and gene disruption. In this study we describe a range of refinements of the method, including stable cell lines expressing Cas9, and a PCR based protocol for the generation of the sgRNA. We also describe a simple methodology that allows both elimination of Cas9 from cells after gene disruption and re-introduction of the disrupted gene. This advance enables easy assessment of the off target effects associated with gene disruption, as well as phenotype-based structure-function analysis. In our study, we used the Fan1 DNA repair gene as control in these experiments. Cas9/CRISPR-mediated Fan1 disruption occurred at frequencies of around 29%, and resulted in the anticipated spectrum of genotoxin hypersensitivity, which was rescued by re-introduction of Fan1

The Leishmania donovani species complex: A new insight into taxonomy.

Among the 20 or so Leishmania spp. described as pathogenic for humans, those of the Leishmania donovani complex are the exclusive causative agents of systemic and fatal visceral leishmaniasis. Although well studied, the complex is taxonomically controversial, which hampers clinical and epidemiological research. In this work, we analysed 56 Leishmania strains previously identified as L. donovani, Leishmania archibaldi or Leishmania infantum, isolated from humans, dogs and sandfly vectors throughout their distribution area. The strains were submitted to biochemical and genetic analyses and the resulting data were compared for congruence. Our results show: i) a partial concordance between biochemical and genetic-based data, ii) very limited genetic variability within the L. donovani complex, iii) footprints of frequent genetic exchange along an east-west gradient, marked by a widespread diffusion of alleles across the geographical range, and iv) a large-scale geographical spreading of a few genotypes. From a taxonomic point of view, considering the absence of relevant terminology in existing classes, the L. donovani complex could be treated as a single entit

UFMylation of MRE11 is essential for telomere length maintenance and hematopoietic stem cell survival

International audienc

mTert induction in p21-positive cells counteracts capillary rarefaction and pulmonary emphysema

Lung diseases develop when telomeres shorten beyond a critical point. We constructed a mouse model in which the catalytic subunit of telomerase (mTert), or its catalytically inactive form (mTert), is expressed from the p21 locus. Expression of either TERT or TERT reduces global p21 levels in the lungs of aged mice, highlighting TERT non-canonical function. However, only TERT reduces accumulation of very short telomeres, oxidative damage, endothelial cell (ECs) senescence and senile emphysema in aged mice. Single-cell analysis of the lung reveals that p21 (and hence TERT) is expressed mainly in the capillary ECs. We report that a fraction of capillary ECs marked by CD34 and endowed with proliferative capacity declines drastically with age, and this is counteracted by TERT but not TERT. Consistently, only TERT counteracts decline of capillary density. Natural aging effects are confirmed using the experimental model of emphysema induced by VEGFR2 inhibition and chronic hypoxia. We conclude that catalytically active TERT prevents exhaustion of the putative CD34 + EC progenitors with age, thus protecting against capillary vessel loss and pulmonary emphysema.Work in VG’s Lab is supported by “La Ligue Contre le Cancer”, Equipe Labellisée, The Canceropole PACA (Projet Emergent), the “Institut National du Cancer” (INCA), PLBIO 2019, and the cross-cutting Inserm program on aging (AGEMED). SA’s Lab is supported by grants from the Inserm, Ministère de la Recherche, Agence Nationale pour la Recherche (ANR), Institut National du Cancer (INCA), and Fondation pour la Recherche Médicale (FRM), et la Fondation ARC. AL-V’s lab is supported by INCa (PLBIO2019) and La Ligue contre le cancer-Paris (RS21/75-24). SC-A is a recipient of a European CO-FUND PhD fellowship from Institut Curie (European Union’s Horizon 2020 research and innovation program under the Marie Skłodowska-Curie grant agreement No 666003). IF’s lab was funded by grants from the Spanish Ministry of Science and Innovation (PID2019-110339RB-I00) and the Comunidad de Madrid (S2017/BMD-3875). EG’s lab was supported by the Fondation ARC (Program ARC), and the cross-cutting Inserm program on aging (AGEMED). CIPHE is supported by PHENOMIN (French National Infrastructure for mouse Phenogenomics; ANR10-INBS-07)

Could conservative iron chelation lead to neuroprotection in amyotrophic lateral sclerosis?

Iron accumulation has been observed in mouse models and both sporadic and familial forms of Amyotrophic lateral sclerosis. Iron chelation could reduce iron accumulation and the related excess of oxidative stress in the motor pathways. However, classical iron chelation would induce systemic iron depletion. We assess the safety and efficacy of conservative iron chelation (i.e. chelation with low risk of iron depletion) in a murine preclinical model and pilot clinical trial. In Sod1G86R mice, deferiprone increased the mean life span as compared with placebo. The safety was good, without anemia after 12 months of deferiprone in the 23 ALS patients enrolled in the clinical trial. The decreases in the ALS Functional Rating Scale and the body mass index (BMI) were significantly smaller for the first 3 months of deferiprone treatment (30 mg/kg/day) than for the first treatment-free period. Iron levels in the cervical spinal cord, medulla oblongata and motor cortex (according to MRI), as well as cerebrospinal fluid levels of oxidative stress and neurofilament light chains were lower after deferiprone treatment. Our observation leads to the hypothesis that moderate iron chelation regimen that avoids changes in systemic iron levels may constitute a novel therapeutic modality of neuroprotection for ALS

Mort cellulaire induite par les sphingolipides et signalisation calcique chez les végétaux

En réponse à une attaque des plantes par un microorganisme pathogène, les LCBs (« sphingoïd Long Chain Bases ») participent à la mise en place d'une mort cellulaire programmée (PCD). Cependant, peu de connaissances existent sur les mécanismes de signalisation des LCBs chez les plantes. Dans ce contexte, les relations croisées entre calcium et ROS (Reactive Oxygen Species) dans la PCD induite par les LCBs ont été étudiées chez les cellules de tabac BY-2. Ainsi, le calcium cytosolique contrôlerait à la fois la PCD et une voie de défense basale impliquant les ROS, tandis que le calcium nucléaire contrôlerait uniquement la PCD. De plus, une phosphorylation des protéines 14-3-3 et des modifications de leurs protéines cibles ont été démontrées chez Arabidopsis thaliana en réponse aux LCBs. En parallèle, une perte d'interaction dépendante du calcium entre CPK3 et les 14-3-3s a été mise en évidence et CPK3 a été identifiée comme la protéine kinase responsable de la phosphorylation des 14-3-3s.LCBs (Long Chain Bases) are involved in Programmed Cell Death (PCD) induced during plant-microorganism interactions. However, little is known about the mechanisms involved in LCB signaling in plants. In the present work, study of crosstalks between calcium and ROS (Reactive Oxygen Species) in tobacco BY-2 cells showed that cytosolic calcium controls both PCD and basal defence processes involving ROS, whereas nuclear calcium only controls PCD. Moreover, LCBs induce 14-3-3 phosphorylation on serine 58 and modifications of 14-3-3 targets including CPK3 in Arabidopsis thaliana cells. Interestingly, the LCB treatment leads to a calcium-dependent disruption of the CPK3/14-3-3 complex. Finally, CPK3 was identified as a kinase able to phosphorylate 14-3-3s in response to LCBs