Regional distribution of the leucine-rich glioma inactivated (LGI) gene family transcripts in the adult mouse brain

25 p., figuras y bibliografíaThe leucine-rich glioma inactivated (LGI) gene subfamily contains four highly conserved members (LGI1, 2, 3 and 4), which have been described in human, mouse and other mammalians. Although their main roles remain unknown, LGI1 gene mutations have been found in human partial temporal lobe epilepsy. Moreover, previous studies showed that the products of these genes exert their function in the nervous system. The anatomical distribution of these gene transcripts in the brain might give some insight to elucidate their possible function. In this study, the pattern of expression of the four LGI genes was assessed in the brain of C57BL/6J adult mice by in situ hybridization. We found that the LGI1 transcript is mainly expressed in the dentate gyrus and CA3 field of the hippocampus. LGI2 and LGI4 genes, which showed a similar pattern of distribution with minor differences, were mostly expressed in the medial septal area, thalamic reticular nucleus and substantia nigra pars compacta. LGI3-expressing cells were distributed widespread, but were more consistently observed in the hippocampal formation, thalamic and hypothalamic nuclei, substantia nigra and reticular formation. In summary, LGI1 gene expression is very restricted to intrahippocampal circuitry, which might be related to its involvement in temporal lobe epilepsy. The patterns of expression of LGI2 and LGI4 genes are very similar and their distribution in the vertical limb of the diagonal band and in putative hippocampal interneurons, suggest that the function of these genes might be related to the generation of hippocampal theta rhythm. Finally, LGI3 gene widespread expression in the brain suggests that its transcripts might be involved in a common cellular process present in different neuronal types.This work was supported by a grant from the Ministerio de Educación y Ciencia (SAF2006-00724) to J. P-T. Part of F. O-B. work has been supported by the Spanish Health Department (FIS 06-1816).Peer reviewe

p27Kip1 regulates alpha-synuclein expression

Alpha-synuclein (α-SYN) is the main component of anomalous protein aggregates (Lewy bodies) that play a crucial role in several neurodegenerative diseases (synucleinopathies) like Parkinson's disease and multiple system atrophy. However, the mechanisms involved in its transcriptional regulation are poorly understood. We investigated here the role of the cyclin-dependent kinase (Cdk) inhibitor and transcriptional regulator p27Kip1 (p27) in the regulation of α-SYN expression. We observed that selective deletion of p27 by CRISPR/Cas9 technology in neural cells resulted in increased levels of α-SYN. Knock-down of the member of the same family p21Cip1 (p21) also led to increased α-SYN levels, indicating that p27 and p21 collaborate in the repression of α-SYN transcription. We demonstrated that this repression is mediated by the transcription factor E2F4 and the member of the retinoblastoma protein family p130 and that it is dependent of Cdk activity. Chromatin immunoprecipitation analysis revealed specific binding sites for p27, p21 and E2F4 in the proximal α-SYN gene promoter. Finally, luciferase assays revealed a direct action of p27, p21 and E2F4 in α-SYN gene expression. Our findings reveal for the first time a negative regulatory mechanism of α-SYN expression, suggesting a putative role for cell cycle regulators in the etiology of synucleinopathies

Neural stem cell regulation by adhesion molecules within the subependymal niche

In the mammalian adult brain, neural stem cells persist in neurogenic niches. The subependymal zone is the most prolific neurogenic niche in adult rodents, where residing stem cells generate large numbers of immature neurons that migrate into the olfactory bulb, where they differentiate into different types of interneurons. Subependymal neural stem cells derive from embryonic radial glia and retain some of their features like apico-basal polarity, with apical processes piercing the ependymal layer, and a basal process contacting blood vessels, constituting an epithelial niche. Conservation of the cytoarchitecture of the niche is of crucial importance for the maintenance of stem cells and for their neurogenic potential. In this minireview we will focus on extracellular matrix and adhesion molecules in the adult subependymal zone, showing their involvement not only as structural elements sustaining the niche architecture and topology, but also in the maintenance of stemness and regulation of the quiescence-proliferation balance.MINECO grants SAF2015-67756R, RYC2014-15591, and FEDER to E

Caracterización genética y funcional del gen causante de la Epilepsia Lateral Temporal Autosómica Dominante

En el primer capítulo se presenta el trabajo de identificación del gen causante de la Epilepsia Lateral Temporal Autosómica Dominante (ADLTE) mediante un rastreo de genes candidatos en familias afectadas. Una vez identificado dicho gen se procedió a diseñar las estrategias necesarias para su caracterización según la información disponible sobre el gen en aquel momento. El segundo capítulo se centra en los resultados obtenidos sobre la naturaleza de la proteína codificada por el gen identificado, tratando de ampliar los escasos datos publicados hasta esa fecha (tan sólo dos trabajos hasta el año 2000). Para ello se analiza la estructura de dominios mediante herramientas bioinformáticas, se estudia el patrón de expresión mediante anticuerpos policlonales y se identifican posibles proteínas de interacción con la técnica del Doble Híbrido en levadura. Finalmente, en el capítulo tercero se formula una hipótesis de trabajo, basada en los datos obtenidos en el capítulo anterior, acerca de la posible ruta celular en la que se encuentra implicado el gen causante de ADLTE. Para su comprobación se presentan un conjunto de ensayos bioquímicos y pruebas funcionales in vitro sobre cultivos celulares cuya interpretación conduce a una propuesta de función para el gen objeto de este estudio. Dicha propuesta requerirá de futuros trabajos para su completa comprobación y caracterización, pero como suele suceder en Ciencia, uno siempre abre más puertas de las que es capaz de cerrar…Para la realización de esta tesis, el autor ha sido beneficiario de una beca del Programa de Formación de Profesorado Universitario (referencia AP2000-0890) concedida por el Ministerio de Educación, Cultura y Deporte (convocatoria BOE 21-11-00) según Resolución de 10 de abril de 2001 de la Dirección General de Universidades y una beca CSIC-Fundación Bancaja para la Formación del Personal Investigador (convocatoria BOE de 20 de enero de 2005). Este trabajo se ha enmarcado dentro del proyecto “Caracterización funcional de Epitempina, el gen responsable de la Epilepsia lateral temporal” financiado por el Ministerio de Ciencia y Tecnología (número de referencia SAF2002-00060).Peer reviewe

The epilepsy gene LGI1 encodes a secreted glycoprotein that binds to the cell surface

This is a pre-copy-editing, author-produced PDF of an article accepted for publication in Human Molecular Genetics following peer review. The definitive publisher-authenticated version Human Molecular Genetics 2006 15(23):3436-3445. is available online at: http://hmg.oxfordjournals.org/cgi/content/full/15/23/3436Autosomal dominant lateral temporal epilepsy (ADTLE) is a partial epilepsy caused by mutations in LGI1, a multidomain protein of unknown function. To begin to understand the biological function of LGI1, we have determined its pattern of glycosylation, subcellular expression and capacity for secretion. LGI1 is expressed as two different isoforms in the brain, and we show that the long isoform is a secreted protein, whereas the short isoform is retained in an intracellular pool. ADLTE-related mutants of the long form are defective for secretion and are retained in the endoplasmic reticulum and Golgi complex. Finally, we show that normal secreted LGI1 specifically binds to the cell surface of differentiated PC12 cells. We propose that LGI1 is a secreted factor important for neuronal development and that ADTLE is a disease that results from the loss of regulation in the protein available either extracellular or intracellularly.This work was supported by grants from the Ministerio de Educación y Ciencia (SAF2002-00060 and SAF2005-00136) to J.P.T. and from the Canadian Institute of Heath Research (PPP147918) to P.A.B. S.S.P. is funded by a fellowship of the Generalitat Valenciana (CTBPRB/2002/35), J.M.M.R. is funded by an FPU and a Bancaixa fellowship. Support from the Ministerio de Educación y Ciencia (BES-2003-0243, to A.A.I.) and from the Ministerio de Sanidad y Consumo (BF03/00182, to V.H.P.) is also acknowledged. K.F. is funded by a Canadian NSERC award.Peer reviewe

MT5-MMP regulates adult neural stem cell functional quiescence through the cleavage of N-cadherin

The identification of mechanisms that maintain stem cell niche architecture and homeostasis is fundamental to our understanding of tissue renewal and repair. Cell adhesion is a well-characterized mechanism for developmental morphogenetic processes, but its contribution to the dynamic regulation of adult mammalian stem cell niches is still poorly defined. We show that N-cadherin-mediated anchorage of neural stem cells (NSCs) to ependymocytes in the adult murine subependymal zone modulates their quiescence. We further identify MT5-MMP as a membrane-type metalloproteinase responsible for the shedding of the N-cadherin ectodomain in this niche. MT5-MMP is co-expressed with N-cadherin in adult NSCs and ependymocytes and, whereas MT5-MMP-mediated cleavage of N-cadherin is dispensable for the regulation of NSC generation and identity, it is required for proper activation of NSCs under physiological and regenerative conditions. Our results indicate that the proliferative status of stem cells can be dynamically modulated by regulated cleavage of cell adhesion molecules

The rates of adult neurogenesis and oligodendrogenesis are linked to cell cycle regulation through p27-dependent gene repression of SOX2

Cell differentiation involves profound changes in global gene expression that often has to occur in coordination with cell cycle exit. Because cyclin-dependent kinase inhibitor p27 reportedly regulates proliferation of neural progenitor cells in the subependymal neurogenic niche of the adult mouse brain, but can also have effects on gene expression, we decided to molecularly analyze its role in adult neurogenesis and oligodendrogenesis. At the cell level, we show that p27 restricts residual cyclin-dependent kinase activity after mitogen withdrawal to antagonize cycling, but it is not essential for cell cycle exit. By integrating genome-wide gene expression and chromatin accessibility data, we find that p27 is coincidentally necessary to repress many genes involved in the transit from multipotentiality to differentiation, including those coding for neural progenitor transcription factors SOX2, OLIG2 and ASCL1. Our data reveal both a direct association of p27 with regulatory sequences in the three genes and an additional hierarchical relationship where p27 repression of Sox2 leads to reduced levels of its downstream targets Olig2 and Ascl1. In vivo, p27 is also required for the regulation of the proper level of SOX2 necessary for neuroblasts and oligodendroglial progenitor cells to timely exit cell cycle in a lineage-dependent manner