State‐of‐the‐art therapies for Rett syndrome Panayotis, Nicolas; Ehinger, Yann; Felix, Marie Solenne ...
Developmental medicine and child neurology,
February 2023, Letnik:
65, Številka:
2
Journal Article
Recenzirano
Odprti dostop
Rett syndrome (RTT) is an X‐linked neurogenetic disorder caused by mutations of the MECP2 (methyl‐CpG‐binding protein 2) gene. Over two decades of work established MeCP2 as a protein with pivotal ...roles in the regulation of the epigenome, neuronal physiology, synaptic maintenance, and behaviour. Given the genetic aetiology of RTT and the proof of concept of its reversal in a mouse model, considerable efforts have been made to design therapeutic approaches to re‐express MeCP2. By being at the forefront of the development of innovative gene therapies, research on RTT is of paramount importance for the treatment of monogenic neurological diseases. Here we discuss the recent advances and challenges of promising genetic strategies for the treatment of RTT including gene replacement therapies, gene/RNA editing strategies, and reactivation of the silenced X chromosome.
What this paper adds
Recent advances shed light on the promises of gene replacement therapy with new vectors designed to control the levels of MeCP2 expression.
New developments in DNA/RNA editing approaches or reactivation of the silenced X chromosome open the possibility to re‐express the native MeCP2 locus at endogenous levels.
Current strategies still face limitations in transduction efficiency and future work is needed to improve brain delivery.
What this paper adds
Recent advances shed light on the promises of gene replacement therapy with new vectors designed to control the levels of MeCP2 expression.
New developments in DNA/RNA editing approaches or reactivation of the silenced X chromosome open the possibility to re‐express the native MeCP2 locus at endogenous levels.
Current strategies still face limitations in transduction efficiency and future work is needed to improve brain delivery.
In this article, we review the recent advances and challenges in the development of innovative therapeutic strategies to treat Rett syndrome, including gene replacement therapy, DNA/RNA editing, and reactivation of the inactive X‐chromosome.
This open access book offers an updated examination of the institutionalisation of political science in sixteen latecomer or peripheral countries in Europe. Its main theme is how political science as ...a science of democracy is influenced and how it responds to the challenges of the new millennium. The chapters, built upon a common theoretical framework of institutionalisation, are evidence-based and comparative. Overall, the book diagnoses diversity among the country cases due to their take-off points and varied political and economic trajectories.
Abstract
Uniaxial strain‐controlled fatigue tests were carried out on a 304L austenitic stainless‐steel specimens in air at 300°C and in pressurized water reactor (PWR), without or with the ...application of a mean stress, at different total strain amplitudes. For strain amplitude no less than 0.2%, a deleterious effect of PWR water on fatigue life is observed, associated with the enhancement of both crack initiation and propagation. Besides, the fatigue life is reduced by the application of a mean stress for a fixed strain amplitude in a given environment. In particular, due to the acceleration of crack initiation stage by an enhancement of the plastic strain accumulation, the PWR water effect on fatigue life is re‐activated for strain amplitude below 0.2% in the presence of a mean stress. The fatigue life reduction under mean stress application is mostly related to the maximum stress level and strain amplitude, rather than the generated ratcheting strain.
Highlights
The results of strain‐controlled fatigue tests in air and in PWR water are presented.
The application of a mean stress affects the fatigue strength in both environments.
The effect of environment and mean stress on initiation and propagation is analyzed.
A modified SWT equation is proposed.
This contribution gives a comprehensive review about the progress in preparation methods, properties and applications of the different synthetic talc types: i) crystalline nanotalc synthesized by ...hydrothermal treatment; ii) amorphous and/or short‐range order nanotalc obtained by precipitation, and iii) organic–inorganic hybrid talc‐like structures obtained through a sol–gel process or a chemical grafting. Several advantages of nanotalc such as high chemical purity, high surface area, tunable submicronic size, high thermal stability, and hydrophilic character (leading to be the first fluid mineral) are emphasized. Synthetic nanotalc applications are also considered including its use as nanofiller in composite materials, as absorbers of organic compounds, as anticorrosion coatings and as agents for cosmetic applications. Regarding their high industrial application potential, intensive research has been carried out to better understand their behavior and develop processes to produce them. To facilitate further research and development, scientific and technical challenges are discussed in this Review article.
In the making: The growing interest in synthetic talc for polymer reinforcement and new cosmetic formulations has motivated research to propose novel synthesis routes based on the chemistry of materials. In this context, over the past 30 years, the synthesis process of talc has evolved noticeably leading to processes which could fulfill industrial requirements. In this Review, the different natures, the synthesis methods and the applications of synthetic nanotalc are enlightened with a focus on the crystalline nanotalc.
Arbuscular mycorrhizal fungi Mathieu, Stephanie; Cusant, Loïc; Roux, Christophe ...
New phytologist,
December 2018, Letnik:
220, Številka:
4
Journal Article
Recenzirano
Odprti dostop
Arbuscular mycorrhizal fungi (AMF) are ubiquitous plant symbionts with an intriguing population biology. Conspecific AMF strains can vary substantially at the genetic and phenotypic levels, leading ...to direct and quantifiable variation in plant growth. Recent studies have shown that high intraspecific diversity is very common in AMF, and not only found in model species. Studies have also revealed how the phenotype of conspecific isolates varies depending on the plant host, highlighting the functional relevance of intraspecific phenotypic plasticity for the AMF ecology and mycorrhizal symbiosis. Recent work has also demonstrated that conspecific isolates of the model AMF Rhizophagus irregularis harbor large and highly variable pangenomes, highlighting the potential role of intraspecific genome diversity for the ecological adaptation of these symbionts.
This paper revisits the concept of crisis within the field of crisis management and puts forward a series of avenues for building a theory of crisis that is in closer relation with the mainstream of ...organization theory. We suggest that if crisis management still limits itself to the analysis of exceptional situations, it might never go beyond the sphere of exception management and will for a long time remain an isolated discipline with little room for innovation and progress. As an alternative we analyze crises as a process of incubation that starts long before the triggering event. This proposition implies revisiting other related notions that have seldom been discussed by authors: first the status and place of the triggering event that should be viewed both as a fault line and a hinge between a degenerative organizational past evolution and a future of change; second, the temporality of a crisis so as to extract it from the urgency it is traditionally associated with; third and contrary to authors who see in the crisis a collapse of meaning and of sensemaking, we analyze it as a surge of meaning that fosters organizational change and transformations.
Rett syndrome (RTT) is a severe X-linked neurodevelopmental disorder that is primarily caused by mutations in the methyl CpG binding protein 2 gene (MECP2). RTT is the second most prevalent genetic ...cause of intellectual disability in girls, and there is currently no cure for the disease. We have previously shown that gene therapy using a self-complementary AAV9 viral vector expressing a codon-optimized Mecp2 version (AAV9-MCO) significantly improved symptoms and increased survival in male Mecp2-deficient mice. Here, we pursued our studies and investigated the safety and efficacy of long-term gene therapy in the genetically relevant RTT mouse model: the heterozygous (HET) Mecp2 deficient female mouse. These mice were injected with the AAV9-MCO vector through the tail vein and an array of behavioral tests was performed. At 16- and 30-weeks post-injection, this treatment was able to rescue apneas and improved the spontaneous locomotor deficits and circadian locomotor activity in Mecp2 HET mice treated with AAV9-MCO at a dose of 5 × 1011 vg/mouse.
To examine whether a higher dose of vector could result in increased improvements, we injected Mecp2 HET mice with a higher MCO vector dose (1012 vg/mouse), which resulted in some severe, sometimes lethal, side effects. In order to confirm these effects, a new cohort of Mecp2 HET mice were administered increasing doses of MCO vector (1011, 5 × 1011 and 1012 vg/mouse). Again, two weeks after vector administration, some Mecp2 HET mice were found dead while others displayed severe side effects and had to be euthanized. These deleterious effects were not observed in Mecp2 HET mice injected with a high dose of AAV9-GFP and were directly proportionate to vector dosage (0, 23 or 54% mortality at an AAV9-MCO dose of 1011, 5 × 1011, 1012 vg/mouse, respectively), and no such lethality was observed in wild-type (WT) mice.
In the Mecp2 HET mice treated with the high and medium AAV9-MCO doses, blood chemistry analysis and post-mortem histology showed liver damage with drastically elevated levels of liver transaminases and disorganized liver architecture. Apoptosis was confirmed by the presence of TUNEL- and cleaved-caspase 3-positive cells in the Mecp2 HET mice treated with the higher doses of AAV9-MCO. We then studied the involvement of the unfolded protein response (UPR) in triggering apoptosis since it can be activated by AAV vectors. Increased expression of the C/EBP homologous protein (CHOP), one of UPR downstream effectors, was confirmed in Mecp2 HET mice after vector administration.
The toxic reaction seen in some treated mice indicates that, although gene therapy for RTT improved breathing deficits observed in Mecp2 HET mice, further studies are needed to better understand the underlying mechanisms and caution must be exercised before similar attempts are undertaken in female Rett patients.
•Treatment of female RTT mice with AAV9-MCO only rescued apneas occurrence.•Using a higher vector dose caused severe off target effects specific to RTT mice.•Post-mortem analysis revealed damaged liver with high CHOP levels and TUNEL expression.•Off target Mecp2 expression may have led to UPR activation and subsequent apoptosis.•These contrasting results underscore the need for additional work to limit side effects.
Objective
Early onset epileptic encephalopathy with suppression‐burst is one of the most severe epilepsy phenotypes in human patients. A significant proportion of cases have a genetic origin, and the ...most frequently mutated gene is KCNQ2, encoding Kv7.2, a voltage‐dependent potassium channel subunit, leading to so‐called KCNQ2‐related epileptic encephalopathy (KCNQ2‐REE). To study the pathophysiology of KCNQ2‐REE in detail and to provide a relevant preclinical model, we generated and described a knock‐in mouse model carrying the recurrent p.(Thr274Met) variant.
Methods
We introduced the p.(Thr274Met) variant by homologous recombination in embryonic stem cells, injected into C57Bl/6N blastocysts and implanted in pseudopregnant mice. Mice were then bred with 129Sv Cre‐deleter to generate heterozygous mice carrying the p.(Thr274Met), and animals were maintained on the 129Sv genetic background. We studied the development of this new model and performed in vivo electroencephalographic (EEG) recordings, neuroanatomical studies at different time points, and multiple behavioral tests.
Results
The Kcnq2Thr274Met/+ mice are viable and display generalized spontaneous seizures first observed between postnatal day 20 (P20) and P30. In vivo EEG recordings show that the paroxysmal events observed macroscopically are epileptic seizures. The brain of the Kcnq2Thr274Met/+ animals does not display major structural defects, similar to humans, and their body weight is normal. Kcnq2Thr274Met/+ mice have a reduced life span, with a peak of unexpected death occurring for 25% of the animals by 3 months of age. Epileptic seizures were generally not observed when animals grew older. Behavioral characterization reveals important deficits in spatial learning and memory in adults but no gross abnormality during early neurosensory development.
Significance
Taken together, our results indicate that we have generated a relevant model to study the pathophysiology of KCNQ2‐related epileptic encephalopathy and perform preclinical research for that devastating and currently intractable disease.
Arbuscular mycorrhizal fungi (AMF) are known to improve plant fitness through the establishment of mycorrhizal symbioses. Genetic and phenotypic variations among closely related AMF isolates can ...significantly affect plant growth, but the genomic changes underlying this variability are unclear.
To address this issue, we improved the genome assembly and gene annotation of the model strain Rhizophagus irregularis DAOM197198, and compared its gene content with five isolates of R. irregularis sampled in the same field.
All isolates harbor striking genome variations, with large numbers of isolate-specific genes, gene family expansions, and evidence of interisolate genetic exchange. The observed variability affects all gene ontology terms and PFAM protein domains, as well as putative mycorrhiza-induced small secreted effector-like proteins and other symbiosis differentially expressed genes. High variability is also found in active transposable elements.
Overall, these findings indicate a substantial divergence in the functioning capacity of isolates harvested from the same field, and thus their genetic potential for adaptation to biotic and abiotic changes. Our data also provide a first glimpse into the genome diversity that resides within natural populations of these symbionts, and open avenues for future analyses of plant–AMF interactions that link AMF genome variation with plant phenotype and fitness.
A recent study published by Mateus et al. 1 claimed that 18 "mating-related" genes are differentially expressed in the model arbuscular mycorrhizal fungus (AMF) Rhizophagus irregularis when ...genetically distinct fungal strains co-colonize a host plant. To clarify the level of evidence for this interesting conclusion, we first aimed to validate the functional annotation of these 18 R. irregularis genes using orthology predictions. These analyses revealed that, although sequence relationship exists, only 2 of the claimed 18 R. irregularis mating genes are potential orthologues to validated fungal mating genes. We also investigated the RNA-seq data from Mateus et al. 1 using classical RNA-seq methods and statistics. This analysis found that the over-expression during strain co-existence was not significant at the typical cut-off of the R. irregularis strains DAOM197198 and B1 in plants. Overall, we do not find convincing evidence that the genes involved have functions in mating, or that they are reproducibly up or down regulated during co-existence in plants.
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