Gliogenesis Depends on glide/gcm through Asymmetric Division of Neuroglioblasts

AbstractSome neurons and glial cells originate from neuroblasts and glioblasts, stem cells that delaminate from the ectoderm of developing fly embryos. A second class of glial cells and neurons differentiates from multipotent precursors, the neuroglioblasts. The differentiation of both glial cell types depends on glial cell deficient/glial cell missing (glide/gcm). Although it has been shown that this transcription factor promotes gliogenesis at the expense of neurogenesis, the cellular mechanisms underlying this fate choice are poorly understood. Using loss and gain of function glide/gcm mutations here we show that the cell fate choice takes place in the neuroglioblast, which divides and produces a glioblast and a neuroblast. Such choice requires the asymmetric distribution of glide/gcm RNA, which accumulates preferentially on one side of the neuroglioblast and is inherited by one cell, the presumptive glioblast. Interestingly, glial cells can differentiate from cells that delaminate as neuroglioblasts or they can arise from cells that start expressing glide/gcm several hours after delamination of a neuroblast. Altogether, these findings identify a novel type of asymmetric cell division and disclose the lineage relationships between glia and neurons. They also reveal the mode of action of the glide/gcm promoting factor

The C-Terminal Domain of CENP-C Displays Multiple and Critical Functions for Mammalian Centromere Formation

CENP-C is a fundamental component of functional centromeres. The elucidation of its structure-function relationship with centromeric DNA and other kinetochore proteins is critical to the understanding of centromere assembly. CENP-C carries two regions, the central and the C-terminal domains, both of which are important for the ability of CENP-C to associate with the centromeric DNA. However, while the central region is largely divergent in CENP-C homologues, the C-terminal moiety contains two regions that are highly conserved from yeast to humans, named Mif2p homology domains (blocks II and III). The activity of these two domains in human CENP-C is not well defined. In this study we performed a functional dissection of C-terminal CENP-C region analyzing the role of single Mif2p homology domains through in vivo and in vitro assays. By immunofluorescence and Chromatin immunoprecipitation assay (ChIP) we were able to elucidate the ability of the Mif2p homology domain II to target centromere and contact alpha satellite DNA. We also investigate the interactions with other conserved inner kinetochore proteins by means of coimmunoprecipitation and bimolecular fluorescence complementation on cell nuclei. We found that the C-terminal region of CENP-C (Mif2p homology domain III) displays multiple activities ranging from the ability to form higher order structures like homo-dimers and homo-oligomers, to mediate interaction with CENP-A and histone H3. Overall, our findings support a model in which the Mif2p homology domains of CENP-C, by virtue of their ability to establish multiple contacts with DNA and centromere proteins, play a critical role in the structuring of kinethocore chromatin

Polycomb Controls Gliogenesis by Regulating the Transient Expression of the Gcm/Glide Fate Determinant

The Gcm/Glide transcription factor is transiently expressed and required in the Drosophila nervous system. Threshold Gcm/Glide levels control the glial versus neuronal fate choice, and its perdurance triggers excessive gliogenesis, showing that its tight and dynamic regulation ensures the proper balance between neurons and glia. Here, we present a genetic screen for potential gcm/glide interactors and identify genes encoding chromatin factors of the Trithorax and of the Polycomb groups. These proteins maintain the heritable epigenetic state, among others, of HOX genes throughout development, but their regulatory role on transiently expressed genes remains elusive. Here we show that Polycomb negatively affects Gcm/Glide autoregulation, a positive feedback loop that allows timely accumulation of Gcm/Glide threshold levels. Such temporal fine-tuning of gene expression tightly controls gliogenesis. This work performed at the levels of individual cells reveals an undescribed mode of Polycomb action in the modulation of transiently expressed fate determinants and hence in the acquisition of specific cell identity in the nervous system. © 2012 Popkova et al.Fondation pour la Recherche Médicale and by Centre Européen de Recherche en Biologie et en Médecine; Association pour la Recherche sur le Cancer; Institut National de la Santé et de la Recherche Médicale; Centre National de la Recherche Scientifique; Université de Strasbourg; Hôpital de Strasbourg; Institut National du Cancer; the Agence Nationale de la Recherche; Alma Mater Studiorum; Università di Bologna; European Research Council (ERC-2008-AdG No 232947); Institut National de la Santé et de la Recherche Médicale; Centre National de la Recherche Scientifique; European Network of Excellence EpiGeneSys; Fundacion Mutua Madrileña (FMM-2006) and Ministerio de Ciencia y Tecnología (BFU-2008-5404)Peer Reviewe

Neuronopathic Gaucher disease models reveal defects in cell growth promoted by Hippo pathway activation

Gaucher Disease (GD), the most common lysosomal disorder, arises from mutations in the GBA1 gene and is characterized by a wide spectrum of phenotypes, ranging from mild hematological and visceral involvement to severe neurological disease. Neuronopathic patients display dramatic neuronal loss and increased neuroinflammation, whose molecular basis are still unclear. Using a combination of Drosophila dGBA1b loss-of-function models and GD patient-derived iPSCs differentiated towards neuronal precursors and mature neurons we showed that different GD- tissues and neuronal cells display an impairment of growth mechanisms with an increased cell death and reduced proliferation. These phenotypes are coupled with the downregulation of several Hippo transcriptional targets, mainly involved in cells and tissue growth, and YAP exclusion from nuclei. Interestingly, Hippo knock-down in the GBA-KO flies rescues the proliferative defect, suggesting that targeting the Hippo pathway can be a promising therapeutic approach to neuronopathic GD.A combination of Drosophila dGBA1b loss-of-function models and Gaucher Disease (GD) patient-derived iPSCs reveals an impairment in GD neuronal cell growth and that Hippo pathway hyperactivation contributes to the impairment

Studio del gene wing-blister di Drosophila melanogastere: analisi genetica e molecolare

Dottorato di ricerca in scienze genetiche. 8. ciclo. Supervisore S. CavicchiConsiglio Nazionale delle Ricerche - Biblioteca Centrale - P.le Aldo Moro, 7, Rome; Biblioteca Nazionale Centrale - P.za Cavalleggeri, 1, Florence / CNR - Consiglio Nazionale delle RichercheSIGLEITItal

Probing the chiral regime of Nf=2 QCD with mixed actions

17 páginas, 15 figuras, 9 tablas.-- El Pdf es la versión pre-print del artículo: arXiv:1008.1870v2We report on our first experiences with a mixed action setup with overlap valence quarks and nonperturbatively O(a) improved Wilson sea quarks. For the latter we employ CLS Nf=2 configurations with light sea-quark masses at small lattice spacings. Exact chiral symmetry allows to consider very light valence quarks and explore the matching to (partially-quenched) Chiral Perturbation Theory (ChPT) in a mixed ϵ/p-regime. We compute the topological susceptibility and the low-lying spectrum of the massless Neuberger-Dirac operator for three values of the sea-quark mass, and compare the sea-quark mass dependence to NLO ChPT in the mixed regime. This provides two different determinations of the chiral condensate, as well as information about some NLOlow-energy couplings. Our results allow to test the consistency of the mixed-regime approach to ChPT, as well as of the mixed action framework.F.B. and C.P. acknowledge nancial support from the FPU grant AP2005-5201 and the Ramón y Cajal Programme, respectively. This work was partially supported by the Spanish Ministry for Education and Science projects FPA2006-05807, FPA2007-60323, FPA2008-01732, FPA2009-08785, HA2008-0057 and CSD2007-00042; the Generalitat Valenciana (PROMETEO/2009/116); the Comunidad Autónoma de Madrid (HEPHACOS P-ESP-00346 and HEPHACOS S2009/ESP-1473); and the European projects FLAVIAnet (MRTN-CT-2006-035482) and STRONGnet (PITN-GA- 2009-238353).Peer reviewe

Empirical and physical modeling of self-heating in power AlGaN/GaN HEMTs

This work shows results of dynamic lumped-element (LE) thermal modeling of power AlGaN/GaN HEMTs. A realistic 3D structure including top-side metals, GaN-Si thermal boundary resistance, die-attach, and source via hole is modeled using a finite-element (FE) tool, and the results are used to develop simplified LE dynamic thermal models. We show that the LE models can match the FE data with excellent accuracy

Mixed action computations on fine dynamical lattices

7 pages, 2 figures.-- En: The XXVII International Symposium on Lattice Field Theory July 26-31, 2009 Peking University, Beijing, ChinaWe report on our first experiences in simulating Neuberger valence fermions on CLS Nf = 2 configurations with light sea quark masses and small lattice spacings. Valence quark masses are considered that allow to explore the matching to (partially quenched) chiral perturbation theory both in the E- and p-regimes. The setup is discussed, and first results are presented for spectral observables.F.B. and C.P. acknowledge financial support from the FPU grant AP2005-5201 and the Ramón y Cajal Programme, respectively. This work was partially supported by the Spanish Ministry for Education and Science projects FPA2006-05807, FPA2006-60323, FPA2008-01732, HA2008- 0057 and CSD2007-00042; the Generalitat Valenciana (PROMETEO/2009/116); the Comunidad Autónoma de Madrid (HEPHACOS P-ESP-00346); and the European project FLAVIAnet (MRTNCT- 2006-035482).Peer reviewe