Local translation in nervous system pathologies

[EN] Dendrites and axons can extend dozens to hundreds of centimeters away from the cell body so that a single neuron can sense and respond to thousands of stimuli. Thus, for an accurate function of dendrites and axons the neuronal proteome needs to be asymmetrically distributed within neurons. Protein asymmetry can be achieved by the transport of the protein itself or the transport of the mRNA that is then translated at target sites in neuronal processes. The latter transport mechanism implies local translation of localized mRNAs. The role of local translation in nervous system (NS) development and maintenance is well established, but recently there is growing evidence that this mechanism and its deregulation are also relevant in NS pathologies, including neurodegenerative diseases. For instance, upon pathological signals diseaserelated proteins can be locally synthesized in dendrites and axons. Locally synthesized proteins can exert their effects at or close to the site of translation, or they can be delivered to distal compartments like the nucleus and induce transcriptional responses that lead to neurodegeneration, nerve regeneration and other cell-wide responses. Relevant key players in the process of local protein synthesis are RNA binding proteins (RBPs), responsible for mRNA transport to neurites. Several neurological and neurodegenerative disorders, including amyotrophic lateral sclerosis or spinal motor atrophy, are characterized by mutations in genes encoding for RBPs and consequently mRNA localization and local translation are impaired. In other diseases changes in the local mRNA repertoire and altered local protein synthesis have been reported. In this review, we will discuss how deregulation of localized translation at different levels can contribute to the development and progression of nervous system pathologies.This work was partially funded by grants awarded to JB (MICINN grants SAF2016-76347-R, RYC-2016-19837, and PID2019-110721RB-I00; The Alzheimer’s Association grants AARG-19-618303 and AARG-19-618303-RAPID). MG and AC are GV fellows; MB-U is a UPV/EHU fellow

RNA Localization and Local Translation in Glia in Neurological and Neurodegenerative Diseases: Lessons from Neurons

Cell polarity is crucial for almost every cell in our body to establish distinct structural and functional domains. Polarized cells have an asymmetrical morphology and therefore their proteins need to be asymmetrically distributed to support their function. Subcellular protein distribution is typically achieved by localization peptides within the protein sequence. However, protein delivery to distinct cellular compartments can rely, not only on the transport of the protein itself but also on the transport of the mRNA that is then translated at target sites. This phenomenon is known as local protein synthesis. Local protein synthesis relies on the transport of mRNAs to subcellular domains and their translation to proteins at target sites by the also localized translation machinery. Neurons and glia specially depend upon the accurate subcellular distribution of their proteome to fulfil their polarized functions. In this sense, local protein synthesis has revealed itself as a crucial mechanism that regulates proper protein homeostasis in subcellular compartments. Thus, deregulation of mRNA transport and/or of localized translation can lead to neurological and neurodegenerative diseases. Local translation has been more extensively studied in neurons than in glia. In this review article, we will summarize the state-of-the art research on local protein synthesis in neuronal function and dysfunction, and we will discuss the possibility that local translation in glia and deregulation thereof contributes to neurological and neurodegenerative diseases.This paper was partially funded by grants awarded to J.B. (MICINN grants SAF2016-76347-R, RYC-2016-19837 and PID2019-110721RB-I00; The Alzheimer’s Association grant AARG-19-618303) and E.A. (MICINN grant PID2019-108465RB-I00; Basque Government grant PIBA-2020-1-0012). M.B.-U. is a UPV/EHU fellow; A.G.-B. is a FPU (FPU17/04891) fellow; M.G. and A.d.l.C. are GV fellows

Apoptosis in the trabecular meshwork of glaucomatous patients

We established and validated an in toto method to perform TdT-mediated dUTP nick end labeling to study apoptosis in human trabecular meshwork tissue obtained during trabeculectomy in glaucoma patients. In specimens from patients with primary open-angle glaucoma and primary angle-closure glaucoma, we detected a tendency for more apoptotic cells to accumulate in patients with primary open-angle glaucoma. The utility of this method to study apoptosis in the trabecular meshwork is discussed, as well as its application as a tool in biologic samples

Aβ oligomers promote oligodendrocyte differentiation and maturation via integrin β1 and Fyn kinase signaling

Alzheimer´s disease (AD) is characterized by a progressive cognitive decline that correlates with the levels of amyloid β-peptide (Aβ) oligomers. Strong evidences connect changes of oligodendrocyte function with the onset of neurodegeneration in AD. However, the mechanisms controlling oligodendrocyte responses to Aβ are still elusive. Here, we tested the role of Aβ in oligodendrocyte differentiation, maturation, and survival in isolated oligodendrocytes and in organotypic cerebellar slices. We found that Aβ peptides specifically induced local translation of 18.5-kDa myelin basic protein (MBP) isoform in distal cell processes concomitant with an increase of process complexity of MBPexpressing oligodendrocytes. Aβ oligomers required integrin β1 receptor, Src-family kinase Fyn and Ca2+/CaMKII as effectors to modulate MBP protein expression. The pharmacological inhibition of Fyn kinase also attenuated oligodendrocyte differentiation and survival induced by Aβ oligomers. Similarly, using ex vivo organotypic cerebellar slices Aβ promoted MBP upregulation through Fyn kinase, and modulated oligodendrocyte population dynamics by inducing cell proliferation and differentiation. Importantly, application of Aβ to cerebellar organotypic slices enhanced remyelination and oligodendrocyte lineage recovery in lysolecithin (LPC)-induced demyelination. These data reveal an important role of Aβ in oligodendrocyte lineage function and maturation, which may be relevant to AD pathogenesis.This study was supported by the Basque Government (fellowship to T.Q.-L.), University of the Basque Country (UPV/EHU; fellowship to C.O.-S.), CIBERNED and MINECO (fellowship to A.G.-B. FPU17/04891; M.P.S.-R. SAF2013-45084-R and SAF2016-75292-R). We thank S. Marcos, A. Martinez, and L. Escobar for technical assistance

Caracterización del significado funcional de la muerte neural temprana. Procesos de modificación del material genético durante el desarrollo de la retina del ratón

Leída en Universidad Complutense de Madrid. Facultad de Ciencias Químicas el 12-03-2008; 183 págs.El sistema nervioso es un tejido de elevada complejidad, tanto en lo que concierne a los múltiples tipos celulares que lo conforman como a la intrincada red de interconexiones que soporta su sofisticada función. Toda esa diversidad se genera durante el desarrollo, a partir de un neuroepitelio aparentemente indiferenciado formado por células proliferativas multipotentes. Éstas pasan por estadios secuenciales de célula madre neural, progenitor neural, neuroblasto o glioblasto, hasta que finalmente se convierten en neuronas y células de la glía maduras. Así pues, procesos como la proliferación, la diferenciación, la migración y el crecimiento axonal y dendrítico son fundamentales para generar la arquitectura del sistema nervioso y de los circu itos neuronales. El control de estos procesos celulares depende, como cualquier otro proceso biológico, de un balance preciso entre señales intrínsecas a la propia célula y señales extrínsecas procedentes de las células vecinas y la matriz extracelul ar. Sin embargo, los mecanismos concretos de control que llevan a las células neuroepiteliales a generar tal diversidad aún no están bien descritos (Cremisi et al 2003, Valenciano et al 2008). La muerte celular programada es un proceso fisiológico fu ndamental para la correcta morfogénesis y funcionalidad del sistema nervioso central. Este fenómeno es especialmente relevante en neuronas de proyección, según postula la teoría neurotrófica, pero también afecta a otros tipos de neuronas y células de la glía (Kuan et al 2000; Roth and D¿Sa, 2001; Davies, 2003; Buss et al, 2006). Además, en etapas tempranas del desarrollo, el sistema nervioso está sujeto a distintas fases de muerte celular que afectan a células proliferativas y a neuroblastos y g lioblastos recién diferenciados (de la Rosa and de Pablo, 2000; Yeo and Gautier, 2004; Boya and de la Rosa, 2005; Valenciano et al, 2008). Aunque este proceso de muerte neural temprana, mucho menos estudiado, está siendo aceptado por la comunidad ci entífica (Davies, 2003), sus implicaciones fisiológicas y funcionales se desconocen. Uno de los procesos que desencadena la apoptosis, el fenotipo más frecuente de muerte celular programada durante el desarrollo del sistema nervioso, es la generación de lesiones en el DNA. En concreto, las lesiones que afectan a las dos hebras del DNA son las que más comprometen la viabilidad celular. El presente trabajo se basa en las observaciones obtenidas en ratones nulos para diversos genes de reparación dePeer reviewe

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RAG-2 deficiency results in fewer phosphorylated histone H2AX foci, but increased retinal ganglion cell death and altered axonal growth

12 p.-5 fig.-1 tab.DNA double-strand breaks (DSBs), selectively visualized as gamma-H2AX(+) foci, occur during the development of the central nervous system, including the retina, although their origin and biological significance are poorly understood. Mutant mice with DSB repair mechanism defects exhibit increased numbers of gamma-H2AX(+) foci, increased cell death during neural development, and alterations in axonogenesis in the embryonic retina. The aim of this study was to identify putative sources of DSBs. One of the identified DSBs sources is LINE-1 retrotransposition. While we did not detect changes in LINE-1 DNA content during the early period of cell death associated with retinal neurogenesis, retinal development was altered in mice lacking RAG-2, a component of the RAG-1,2-complex responsible for initiating somatic recombination in lymphocytes. Although gamma-H2AX(+) foci were less abundant in the rag2(-/-) mouse retina, retinal ganglion cell death was increased and axonal growth and navigation were impaired in the RAG-2 deficient mice, a phenotype shared with mutant mice with defective DNA repair mechanisms. These findings demonstrate that RAG-2 is necessary for proper retinal development, and suggest that both DSB generation and repair are genuine processes intrinsic to neural development.This work was supported by the Ministerio de Economía y Competitividad, Spain (Grants SAF2013-41059-R and SAF2016-75681R to EJdlR).Peer reviewe

Increased neuronal death and disturbed axonal growth in the Polμ-deficient mouse embryonic retina

13 p.-8 fig.Programmed cell death occurs naturally at different stages of neural development, including neurogenesis. The functional role of this early phase of neural cell death, which affects recently differentiated neurons among other cell types, remains undefined. Some mouse models defective in DNA double-strand break (DSB) repair present massive cell death during neural development, occasionally provoking embryonic lethality, while other organs and tissues remain unaffected. This suggests that DSBs occur frequently and selectively in the developing nervous system. We analyzed the embryonic retina of a mouse model deficient in the error-prone DNA polymerase μ (Polμ), a key component of the non-homologous end-joining (NHEJ) repair system. DNA DSBs were increased in the mutant mouse at embryonic day 13.5 (E13.5), as well as the incidence of cell death that affected young neurons, including retinal ganglion cells (RGCs). Polμ−/− mice also showed disturbed RGC axonal growth and navigation, and altered distribution of the axonal guidance molecules L1-CAM and Bravo (also known as Nr-CAM). These findings demonstrate that Polμ is necessary for proper retinal development, and support that the generation of DSBs and their repair via the NHEJ pathway are genuine processes involved in neural development.This work was supported by the Ministerio de Ciencia e Innovación, Spain (Grant SAF2010-21879 to EJdlR and PdlV), the Ministerio de Economía y Competitividad, Spain (Grant SAF2013-41059-R to EJdlR and Grant BFU2012-37969 to LB), the Comunidad de Madrid, Spain (Grant S2011/BMD-2361 to LB).Peer reviewe

Reparación de roturas de DNA de doble hebra: implicación de la vía de reparación no homóloga en el desarrollo de la retina

Trabajo presentado en el XXXIV Congreso de la Sociedad Española de Bioquímica y Biología Molecular SEBBM, celebrado en Barcelona (España) del 5 al 8 de septiembre de 2011