Characterization of molecular mechanisms underlying the axonal Charcot-Marie-Tooth neuropathy caused by MORC2 mutations

[EN] Mutations in MORC2 lead to an axonal form of Charcot-Marie-Tooth (CMT) neuropathy type 2Z. To date, 31 families have been described with mutations in MORC2, indicating that this gene is frequently involved in axonal CMT cases. While the genetic data clearly establish the causative role of MORC2 in CMT2Z, the impact of its mutations on neuronal biology and their phenotypic consequences in patients remains to be clarified. We show that the full-length form of MORC2 is highly expressed in both embryonic and adult human neural tissues and that Morc2 expression is dynamically regulated in both the developing and the maturing murine nervous system. To determine the effect of the most common MORC2 mutations, p.S87L and p.R252W, we used several in vitro cell culture paradigms. Both mutations induced transcriptional changes in patient-derived fibroblasts and when expressed in rodent sensory neurons. These changes were more pronounced and accompanied by abnormal axonal morphology, in neurons expressing the MORC2 p.S87L mutation, which is associated with a more severe clinical phenotype. These data provide insight into the neuronal specificity of the mutated MORC2-mediated phenotype and highlight the importance of neuronal cell models to study the pathophysiology of CMT2Z.Instituto de Salud Carlos III (ISCIII) - Subdireccion General de Evaluacion y Fomento de la Investigacion within the framework of the National R+D+I Plan (PI15/00187 to C. E. and PI16/00403 to T. S.), co-funded with FEDER funds; Ramon Areces Foundation (CIVP17A2810 to C. E.); Generalitat Valenciana (PROMETEO/2018/135 to C. E. and T. S.); AFM-Telethon (21500 to C. E. and R. C.); National Health and Medical Research Council of Australia Grant (APP1046680 to M. K.); Czech Health Research Council (AZV16-30206A to P. L.); Swedish StratNeuro program grant; Swedish Research Council (2015-02394 to R. C.). C. E. had a 'Miguel Servet' contract funded by the ISCIII and the Centro de Investigacion Principe Felipe (CPII14/00002). P. S. is the recipient of a FPU-PhD fellowship funded by the Spanish Ministry of Education, Culture and Sport [FPU15/00964]. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.Sancho, P.; Bartesaghi, L.; Miossec, O.; García-García, F.; Ramírez-Jiménez, L.; Siddell, A.; Ajkesson, E.... (2019). Characterization of molecular mechanisms underlying the axonal Charcot-Marie-Tooth neuropathy caused by MORC2 mutations. Human Molecular Genetics. 28(10):1629-1644. https://doi.org/10.1093/hmg/ddz00616291644281

PRDM12 Is Required for Initiation of the Nociceptive Neuron Lineage during Neurogenesis

Summary: The sensation of pain is essential for the preservation of the functional integrity of the body. However, the key molecular regulators necessary for the initiation of the development of pain-sensing neurons have remained largely unknown. Here, we report that, in mice, inactivation of the transcriptional regulator PRDM12, which is essential for pain perception in humans, results in a complete absence of the nociceptive lineage, while proprioceptive and touch-sensitive neurons remain. Mechanistically, our data reveal that PRDM12 is required for initiation of neurogenesis and activation of a cascade of downstream pro-neuronal transcription factors, including NEUROD1, BRN3A, and ISL1, in the nociceptive lineage while it represses alternative fates other than nociceptors in progenitor cells. Our results thus demonstrate that PRDM12 is necessary for the generation of the entire lineage of pain-initiating neurons. : The sensation of pain, temperature, and itch by neurons of the nociceptive lineage is essential for animal survival. Bartesaghi et al. report that the transcriptional regulator PRDM12 is indispensable in neural crest cells (NCCs) for the initiation of the sensory neuronal differentiation program that generates the entire nociceptive lineage. Keywords: neurogenesis, pain, nociceptive neurons, Prdm12, neural crest cell

Building the Future Therapies for Down Syndrome:The Third International Conference of the T21 Research Society

Research focused on Down syndrome has increased in the last several years to advance understanding of the consequences of trisomy 21 (T21) on molecular and cellular processes and, ultimately, on individuals with Down syndrome. The Trisomy 21 Research Society (T21RS) is the premier scientific organization for researchers and clinicians studying Down syndrome. The Third International Conference of T21RS, held June 6-9, 2019, in Barcelona, Spain, brought together 429 scientists, families, and industry representatives to share the latest discoveries on underlying cellular and molecular mechanisms of T21, define cognitive and behavioral challenges and better understand comorbidities associated with Down syndrome, including Alzheimer's disease and leukemia. Presentation of cutting-edge results in neuroscience, neurology, model systems, psychology, cancer, biomarkers and molecular and phar-ma-cological therapeutic approaches demonstrate the compelling interest and continuing advancement in all aspects of understanding and ameliorating conditions associated with T21

Leghemoglobin is nitrated in functional legume nodules in a tyrosine residue within the heme cavity by a nitrite/ peroxide-dependent mechanism

41 Pags.- 3 Tabls.- 10 Figs. The definitive version is available at: http://onlinelibrary.wiley.com/journal/10.1111/(ISSN)1365-313XProtein Tyr nitration is a post-translational modification yielding 3-nitrotyrosine (NO2-Tyr). Formation of NO2-Tyr is generally considered as a marker of nitroxidative stress and is involved in some human pathophysiological disorders, but it has been poorly studied in plants. Leghemoglobin (Lb) is an abundant hemeprotein of legume nodules that plays an essential role as O2 transporter. Liquid chromatography coupled to tandem mass spectrometry was used for a targeted search and quantification of NO2-Tyr in Lbs. For all Lbs examined, Tyr30, located in the distal heme pocket, is the major target of nitration. Lower amounts were found for NO2-Tyr25 and NO2-Tyr133. Nitrated Lb and other as yet unidentified nitrated proteins were also detected in nodules of plants not receiving NO3- and were found to decrease during senescence. This demonstrates formation of nitric oxide (•NO) and NO2- by alternative means to nitrate reductase, probably via a NO synthase-like enzyme, and strongly suggests that nitrated proteins perform biological functions and are not merely metabolic byproducts. In vitro assays with purified Lbs revealed that Tyr nitration requires NO2- + H2O2 and that peroxynitrite is not an efficient inducer of nitration, possibly by isomerizing it to NO3-. Nitrated Lb is formed via oxoferryl Lb, which generates nitrogen dioxide and tyrosyl radicals. This mechanism is distinctly different from that involved in heme nitration. Formation of NO2-Tyr in Lbs is a consequence of active metabolism in functional nodules, where Lbs may act as a sink of toxic peroxynitrite and may play a protective role in the symbiosis.M.S. was the recipient of a predoctoral contract (Programa Junta de Ampliación de Estudios) from CSIC. L.C.-B. was the recipient of a predoctoral contract (Formación de Personal Investigador) from Ministerio de Economía y Competitividad (MINECO). C.S. was funded by the Austrian Fonds zur Förderung der wis-senschaftlichen Forschung (P23441-B20). This work was mainly supported by MINECO-Fondo Europeo de Desarrollo Regional (AGL2011-24524 and AGL2014-53717-R) and CSIC (Proyecto Intramural Especial 201240E150). Additional funding was provided by grants of Agencia Nacional de Investigación e Innovación (Fondo Clemente Estable, FCE 6605) to S.B. and Universidad de la República and National Institutes of Health (RO1 AI095173) to R.R.Peer reviewe

Pharmacotherapy with Fluoxetine Restores Functional Connectivity from the Dentate Gyrus to Field CA3 in the Ts65Dn Mouse Model of Down Syndrome

Down syndrome (DS) is a high-incidence genetic pathology characterized by severe impairment of cognitive functions, including declarative memory. Impairment of hippocampus-dependent long-term memory in DS appears to be related to anatomo-functional alterations of the hippocampal trisynaptic circuit formed by the dentate gyrus (DG) granule cells - CA3 pyramidal neurons - CA1 pyramidal neurons. No therapies exist to improve cognitive disability in individuals with DS. In previous studies we demonstrated that pharmacotherapy with fluoxetine restores neurogenesis, granule cell number and dendritic morphology in the DG of the Ts65Dn mouse model of DS. The goal of the current study was to establish whether treatment rescues the impairment of synaptic connectivity between the DG and CA3 that characterizes the trisomic condition. Euploid and Ts65Dn mice were treated with fluoxetine during the first two postnatal weeks and examined 45-60 days after treatment cessation. Untreated Ts65Dn mice had a hypotrophyc mossy fiber bundle, fewer synaptic contacts, fewer glutamatergic contacts, and fewer dendritic spines in the stratum lucidum of CA3, the terminal field of the granule cell projections. Electrophysiological recordings from CA3 pyramidal neurons showed that in Ts65Dn mice the frequency of both mEPSCs and mIPSCs was reduced, indicating an overall impairment of excitatory and inhibitory inputs to CA3 pyramidal neurons. In treated Ts65Dn mice all these aberrant features were fully normalized, indicating that fluoxetine can rescue functional connectivity between the DG and CA3. The positive effects of fluoxetine on the DG-CA3 system suggest that early treatment with this drug could be a suitable therapy, possibly usable in humans, to restore the physiology of the hippocampal networks and, hence, memory functions

Theoretical Models of Consciousness: A Scoping Review

The amount of knowledge on human consciousness has created a multitude of viewpoints and it is difficult to compare and synthesize all the recent scientific perspectives. Indeed, there are many definitions of consciousness and multiple approaches to study the neural correlates of consciousness (NCC). Therefore, the main aim of this article is to collect data on the various theories of consciousness published between 2007–2017 and to synthesize them to provide a general overview of this topic. To describe each theory, we developed a thematic grid called the dimensional model, which qualitatively and quantitatively analyzes how each article, related to one specific theory, debates/analyzes a specific issue. Among the 1130 articles assessed, 85 full texts were included in the prefinal step. Finally, this scoping review analyzed 68 articles that described 29 theories of consciousness. We found heterogeneous perspectives in the theories analyzed. Those with the highest grade of variability are as follows: subjectivity, NCC, and the consciousness/cognitive function. Among sub-cortical structures, thalamus, basal ganglia, and the hippocampus were the most indicated, whereas the cingulate, prefrontal, and temporal areas were the most reported for cortical ones also including the thalamo-cortical system. Moreover, we found several definitions of consciousness and 21 new sub-classifications

Loss of CDKL5 impairs survival and dendritic growth of newborn neurons by altering AKT/GSK-3β signaling.

none10noMutations in the X-linked cyclin-dependent kinase-like 5 (CDKL5) gene have been identified in a neurodevelopmental disorder characterized by early-onset intractable seizures, severe developmental delay, intellectual disability, and Rett's syndrome-like features. Since the physiological functions of CDKL5 still need to be elucidated, in the current study we took advantage of a new Cdkl5 knockout (KO) mouse model in order to shed light on the role of this gene in brain development. We mainly focused on the hippocampal dentate gyrus, a region that largely develops postnatally and plays a key role in learning and memory. Looking at the process of neurogenesis, we found a higher proliferation rate of neural precursors in Cdkl5 KO mice in comparison with wild type mice. However, there was an increase in apoptotic cell death of postmitotic granule neuron precursors, with a reduction in total number of granule cells. Looking at dendritic development, we found that in Cdkl5 KO mice the newly-generated granule cells exhibited a severe dendritic hypotrophy. In parallel, these neurodevelopmental defects were associated with impairment of hippocampus-dependent memory. Looking at the mechanisms whereby CDKL5 exerts its functions, we identified a central role of the AKT/GSK-3β signaling pathway. Overall our findings highlight a critical role of CDKL5 in the fundamental processes of brain development, namely neuronal precursor proliferation, survival and maturation. This evidence lays the basis for a better understanding of the neurological phenotype in patients carrying mutations in the CDKL5 gene.noneFuchs C;Trazzi S;Torricella R;Viggiano R;De Franceschi M;Amendola E;Gross C;Calzà L;Bartesaghi R;Ciani EFuchs C;Trazzi S;Torricella R;Viggiano R;De Franceschi M;Amendola E;Gross C;Calzà L;Bartesaghi R;Ciani

Early Pharmacotherapy with Fluoxetine Rescues Dendritic Pathology in the Ts65Dn Mouse Model of Down Syndrome

Down syndrome DS is a genetic pathology characterized by brain hypotrophy and severe cognitive impairment. Although defective neurogenesis is an important determinant of mental disability, a severe dendritic pathology appears to be an equally important factor. A previous study showed that fluoxetine, a selective serotonin reuptake inhibitor, fully restores neurogenesis in the Ts65Dn mouse model of DS. The goal of the current study was to establish whether fluoxetine also restores dendritic development. In mice aged 45 days, treated with fluoxetine in the postnatal period P3-P15, we examined the dendritic arbor of the granule cells of the dentate gyrus (DG). The granule cells of trisomic mice had a severely hypotrophic dendritic arbor, fewer spines and a reduced innervation than euploid mice. Treatment with fluoxetine fully restored all these defects. In Ts65Dn mice, we found reduced levels of serotonin that were restored by treatment. Results show that a pharmacotherapy with fluoxetine is able to rescue not only the number of granule neurons but also their "quality" in terms of correct maturation and connectivity. These findings strongly suggest that fluoxetine may be a drug of choice for the improvement of the major defects in the DS brain and, possibly, of mental retardation

Leghemoglobin is nitrated in functional legume nodules in a tyrosine residue within the heme cavity by a nitrite/ peroxide-dependent mechanism

Trabajo presentado en la 12th International Conference on Reactive Oxygen and Nitrogen Species in Plants: from model systems to field, celebrada en Verona, Italia, del 24 al 26 de junio de 2015Protein Tyr nitration is a post-translational modification yielding 3-nitrotyrosine (NO2-Tyr). Formation of NO2-Tyr is generally considered as a marker of nitroxidative stress and is involved in some human pathophysiological disorders, but it has been poorly studied in plants. Leghemoglobin (Lb) is an abundant hemeprotein of legume nodules that plays an essential role as O2 transporter. Liquid chromatography coupled to tandem mass spectrometry was used for a targeted search and quantification of NO2-Tyr in Lbs. For all Lbs examined, Tyr30, located in the distal heme pocket, is the major target of nitration. Lower amounts were found for NO2-Tyr25 and NO2-Tyr133. Nitrated Lb and other as yet unidentified nitrated proteins were also detected in nodules of plants not receiving NO3- and were found to decrease during senescence. This demonstrates formation of nitric oxide (NO) and NO2- by alternative means to nitrate reductase, probably via a NO synthase-like enzyme, and strongly suggests that nitrated proteins perform biological functions and are not merely metabolic byproducts. In vitro assays with purified Lbs revealed that Tyr nitration requires NO2- + H2O2 and that peroxynitrite is not an efficient inducer of nitration, possibly by isomerizing it to NO3-. Nitrated Lb is formed via oxoferryl Lb, which generates nitrogen dioxide and tyrosyl radicals. This mechanism is distinctly different from that involved in heme nitration. Formation of NO2-Tyr in Lbs is a consequence of active metabolism in functional nodules, where Lbs may act as a sink of toxic peroxynitrite and may play a protective role in the symbiosis.Peer Reviewe

Long-term effect of neonatal inhibition of APP gamma-secretase on hippocampal development in the Ts65Dn mouse model of Down syndrome

Neurogenesis impairment is considered a major determinant of the intellectual disability that characterizes Down syndrome (DS), a genetic condition caused by triplication of chromosome 21. Previous evidence obtained in the Ts65Dn mouse model of DS showed that the triplicated gene APP (amyloid precursor protein) is critically involved in neurogenesis alterations. In particular, excessive levels of AICD (amyloid precursor protein intracellular domain) resulting from APP cleavage by gamma-secretase increase the transcription of Ptch1, a Sonic Hedgehog (Shh) receptor that keeps the mitogenic Shh pathway repressed. Previous evidence showed that neonatal treatment with ELND006, an inhibitor of gamma-secretase, reinstates the Shh pathway and fully restores neurogenesis in Ts65Dn pups. In the framework of potential therapies for DS, it is extremely important to establish whether the positive effects of early intervention are retained after treatment cessation. Therefore, the goal of the current study was to establish whether early treatment with ELND006 leaves an enduring trace in the brain of Ts65Dn mice. Ts65Dn and euploid pups were treated with ELND006 in the postnatal period P3-P15 and the outcome of treatment was examined at ~\ua0one month after treatment cessation. We found that in treated Ts65Dn mice the pool of proliferating cells in the hippocampal dentate gyrus (DG) and total number of granule neurons were still restored as was the number of pre- and postsynaptic terminals in the stratum lucidum of CA3, the site of termination of the mossy fibers from the DG. Accordingly, patch-clamp recording from field CA3 showed functional normalization of the input to CA3. Unlike in field CA3, the number of pre- and postsynaptic terminals in the DG of treated Ts65Dn mice was no longer fully restored. The finding that many of the positive effects of neonatal treatment were retained after treatment cessation provides proof of principle demonstration of the efficacy of early inhibition of gamma-secretase for the improvement of brain development in DS