Search

[ES] Durante el desarrollo de los circuitos neurales, una gran parte de la comunicación que ocurre entre las señales de orientación ambiental y el citoesqueleto ocurre en la punta distal del axón, en el cono de crecimiento. Los conos de crecimiento (GC) vienen en muchas formas y tamaños, son muy dinámicos y sondean constantemente su entorno extendiendo y retrayendo sus protuberancias. La motilidad del GC está impulsada principalmente por la remodelación coordinada de las redes citoesqueléticas, incluidas las fibras de actina y los microtúbulos. Para el desarrollo de la conectividad retinotalámica, las células ganglionares de la retina (RGC) proyectan sus axones desde la retina hasta los núcleos dorsal del talámico y requieren una guía adecuada de transducción de señales en el quiasma óptico. La mayoría de los axones RGC cruzan la línea media y se proyectan contralateralmente hacia el tálamo del hemisferio opuesto, mientras que una subpoblación de axones RGC son repelidos en el quiasma óptico y crecen ipsilateralmente. El factor de transcripción Zic2 se ha identificado como un determinante de la identidad ipsilateral de las neuronas RGC y puede inducir de forma autónoma una especificación ipsilateral. La presencia de Zic2 en RGC ipsilaterales provoca la señalización dependiente de Ephrin y Wnt en el quiasma óptico y conduce a la fosforilación de ß-catenina en los axones, lo que evita la formación de complejos cadherina / actina. Esto, localmente desestabiliza F-actina y desencadena la respuesta repulsiva. Durante este proyecto TFM, analizamos si Zic2 también desempeña un papel autónomo celular en la determinación del tamaño y la forma de los conos de crecimiento y cómo este factor de transcripción afecta el citoesqueleto de actina F y la dinámica de los conos de crecimiento. Para hacer esto, sobreexpresamos Zic2 en RGCs mediante electroporación in utero en la retina de embriones de ratones y realizamos explantes de retina in vitro. Encontramos que la sobreexpresión d, [EN] During neural circuits development, a large part of the communication that occurs between environmental guiadance signals and the cytoskeleton occurs at the distal tip of the axon, in the growth cone. Growth cones (GC) come in many shapes and sizes, are very dynamic and constantly probe their surroundings by extending and retracting their protrusions. GC motility is mainly driven by the coordinated remodeling of cytoskeletal networks, including the actin fibers and the microtubules. For the development of retinothalamic connectivity, the retinal ganglion cells (RGCs) project their axons from the retina to the dorsal thalamic nuclei and require a proper guidance signaling transduction at the optic chiasm. Most RGC axons cross the midline and project contralaterally towards the thalamus of the opposite hemisphere, whereas a subpopulation of RGC axons are repelled at the optic chiasm and grow ipsilaterally. The transcription factor Zic2 has been identified as a determinant of the ipsilateral identity of RGC neurons and can autonomously induce an ipsilateral specification. The presence of Zic2 in ipsilateral RGCs elicits Ephrin and Wnt-dependent signaling at the optic chiasma and leads to ß-catenin phosphorylation in axons, which prevents the formation of cadherin/actin complexes. This, locally destabilizes F-actin and triggers the repulsive response. During this TFM project, we analyzed whether Zic2 also plays a cell-autonomous role in determining the size and shape of growth cones and how this transcription factor affects the F-actin cytoskeleton and growth cone dynamics. To do this, we overexpressed Zic2 in RGCs by in utero electroporation in the retina of mice embryos and performed retinal explants in vitro. We found that Zic2 overexpression does not significantly change the GC size and filopodia numbers in the axons, but we did observe a strong increase in the F-actin enrichment in the GC periphery of Zic2-expressing RGC axons. The observed increase in F-actin

[ES] Durante el desarrollo de los circuitos neurales, una gran parte de la comunicación que ocurre entre las señales de orientación ambiental y el citoesqueleto ocurre en la punta distal del axón, en el cono de crecimiento. Los conos de crecimiento (GC) vienen en muchas formas y tamaños, son muy dinámicos y sondean constantemente su entorno extendiendo y retrayendo sus protuberancias. La motilidad del GC está impulsada principalmente por la remodelación coordinada de las redes citoesqueléticas, incluidas las fibras de actina y los microtúbulos. Para el desarrollo de la conectividad retinotalámica, las células ganglionares de la retina (RGC) proyectan sus axones desde la retina hasta los núcleos dorsal del talámico y requieren una guía adecuada de transducción de señales en el quiasma óptico. La mayoría de los axones RGC cruzan la línea media y se proyectan contralateralmente hacia el tálamo del hemisferio opuesto, mientras que una subpoblación de axones RGC son repelidos en el quiasma óptico y crecen ipsilateralmente. El factor de transcripción Zic2 se ha identificado como un determinante de la identidad ipsilateral de las neuronas RGC y puede inducir de forma autónoma una especificación ipsilateral. La presencia de Zic2 en RGC ipsilaterales provoca la señalización dependiente de Ephrin y Wnt en el quiasma óptico y conduce a la fosforilación de ß-catenina en los axones, lo que evita la formación de complejos cadherina / actina. Esto, localmente desestabiliza F-actina y desencadena la respuesta repulsiva. Durante este proyecto TFM, analizamos si Zic2 también desempeña un papel autónomo celular en la determinación del tamaño y la forma de los conos de crecimiento y cómo este factor de transcripción afecta el citoesqueleto de actina F y la dinámica de los conos de crecimiento. Para hacer esto, sobreexpresamos Zic2 en RGCs mediante electroporación in utero en la retina de embriones de ratones y realizamos explantes de retina in vitro. Encontramos que la sobreexpresión d, [EN] During neural circuits development, a large part of the communication that occurs between environmental guiadance signals and the cytoskeleton occurs at the distal tip of the axon, in the growth cone. Growth cones (GC) come in many shapes and sizes, are very dynamic and constantly probe their surroundings by extending and retracting their protrusions. GC motility is mainly driven by the coordinated remodeling of cytoskeletal networks, including the actin fibers and the microtubules. For the development of retinothalamic connectivity, the retinal ganglion cells (RGCs) project their axons from the retina to the dorsal thalamic nuclei and require a proper guidance signaling transduction at the optic chiasm. Most RGC axons cross the midline and project contralaterally towards the thalamus of the opposite hemisphere, whereas a subpopulation of RGC axons are repelled at the optic chiasm and grow ipsilaterally. The transcription factor Zic2 has been identified as a determinant of the ipsilateral identity of RGC neurons and can autonomously induce an ipsilateral specification. The presence of Zic2 in ipsilateral RGCs elicits Ephrin and Wnt-dependent signaling at the optic chiasma and leads to ß-catenin phosphorylation in axons, which prevents the formation of cadherin/actin complexes. This, locally destabilizes F-actin and triggers the repulsive response. During this TFM project, we analyzed whether Zic2 also plays a cell-autonomous role in determining the size and shape of growth cones and how this transcription factor affects the F-actin cytoskeleton and growth cone dynamics. To do this, we overexpressed Zic2 in RGCs by in utero electroporation in the retina of mice embryos and performed retinal explants in vitro. We found that Zic2 overexpression does not significantly change the GC size and filopodia numbers in the axons, but we did observe a strong increase in the F-actin enrichment in the GC periphery of Zic2-expressing RGC axons. The observed increase in F-actin

[ES] Durante el desarrollo de los circuitos neurales, una gran parte de la comunicación que ocurre entre las señales de orientación ambiental y el citoesqueleto ocurre en la punta distal del axón, en el cono de crecimiento. Los conos de crecimiento (GC) vienen en muchas formas y tamaños, son muy dinámicos y sondean constantemente su entorno extendiendo y retrayendo sus protuberancias. La motilidad del GC está impulsada principalmente por la remodelación coordinada de las redes citoesqueléticas, incluidas las fibras de actina y los microtúbulos. Para el desarrollo de la conectividad retinotalámica, las células ganglionares de la retina (RGC) proyectan sus axones desde la retina hasta los núcleos dorsal del talámico y requieren una guía adecuada de transducción de señales en el quiasma óptico. La mayoría de los axones RGC cruzan la línea media y se proyectan contralateralmente hacia el tálamo del hemisferio opuesto, mientras que una subpoblación de axones RGC son repelidos en el quiasma óptico y crecen ipsilateralmente. El factor de transcripción Zic2 se ha identificado como un determinante de la identidad ipsilateral de las neuronas RGC y puede inducir de forma autónoma una especificación ipsilateral. La presencia de Zic2 en RGC ipsilaterales provoca la señalización dependiente de Ephrin y Wnt en el quiasma óptico y conduce a la fosforilación de ß-catenina en los axones, lo que evita la formación de complejos cadherina / actina. Esto, localmente desestabiliza F-actina y desencadena la respuesta repulsiva. Durante este proyecto TFM, analizamos si Zic2 también desempeña un papel autónomo celular en la determinación del tamaño y la forma de los conos de crecimiento y cómo este factor de transcripción afecta el citoesqueleto de actina F y la dinámica de los conos de crecimiento. Para hacer esto, sobreexpresamos Zic2 en RGCs mediante electroporación in utero en la retina de embriones de ratones y realizamos explantes de retina in vitro. Encontramos que la sobreexpresión d, [EN] During neural circuits development, a large part of the communication that occurs between environmental guiadance signals and the cytoskeleton occurs at the distal tip of the axon, in the growth cone. Growth cones (GC) come in many shapes and sizes, are very dynamic and constantly probe their surroundings by extending and retracting their protrusions. GC motility is mainly driven by the coordinated remodeling of cytoskeletal networks, including the actin fibers and the microtubules. For the development of retinothalamic connectivity, the retinal ganglion cells (RGCs) project their axons from the retina to the dorsal thalamic nuclei and require a proper guidance signaling transduction at the optic chiasm. Most RGC axons cross the midline and project contralaterally towards the thalamus of the opposite hemisphere, whereas a subpopulation of RGC axons are repelled at the optic chiasm and grow ipsilaterally. The transcription factor Zic2 has been identified as a determinant of the ipsilateral identity of RGC neurons and can autonomously induce an ipsilateral specification. The presence of Zic2 in ipsilateral RGCs elicits Ephrin and Wnt-dependent signaling at the optic chiasma and leads to ß-catenin phosphorylation in axons, which prevents the formation of cadherin/actin complexes. This, locally destabilizes F-actin and triggers the repulsive response. During this TFM project, we analyzed whether Zic2 also plays a cell-autonomous role in determining the size and shape of growth cones and how this transcription factor affects the F-actin cytoskeleton and growth cone dynamics. To do this, we overexpressed Zic2 in RGCs by in utero electroporation in the retina of mice embryos and performed retinal explants in vitro. We found that Zic2 overexpression does not significantly change the GC size and filopodia numbers in the axons, but we did observe a strong increase in the F-actin enrichment in the GC periphery of Zic2-expressing RGC axons. The observed increase in F-actin

Bivalent histone modifications are defined as repressive and activating epigenetic marks that simultaneously decorate the same genomic region. The H3K27me3 mark silences gene expression, while the H3K4me3 mark prevents the region from becoming permanently silenced and prepares the domain for activation when needed. Specific regions of Kaposi's sarcoma-associated herpesvirus (KSHV) latent episomes are poised to be activated by the KSHV replication and transcription activator (K-Rta). How KSHV episomes are prepared such that they maintain latent infection and switch to lytic replication by K-Rta remains unclear. K-Rta transactivation activity requires a protein degradation function; thus, we hypothesized that identification of cellular substrates of K-Rta may provide insight into the maintenance of KSHV latent infection and the switch to lytic replication. Here we show that a zinc finger protein, ZIC2, a key regulator for central nervous system development, is a substrate of K-Rta and is responsible for maintaining latency. K-Rta directly interacted with ZIC2 and functioned as an E3 ligase to ubiquitinate ZIC2. ZIC2 localized at immediate early and early gene cluster regions of the KSHV genome and contributed to tethering of polycomb repressive complex 2 through physical interaction, thus maintaining H3K27me3 marks at the K-Rta promoter. Accordingly, depletion of ZIC2 shifted the balance of bivalent histone modifications toward more active forms and induced KSHV reactivation in naturally infected cells. We suggest that ZIC2 turnover by K-Rta is a strategy employed by KSHV to favor the transition from latency to lytic replication.IMPORTANCE Posttranslational histone modifications regulate the accessibility of transcriptional factors to DNA; thus, they have profound effects on gene expression (e.g., viral reactivation). KSHV episomes are known to possess bivalent chromatin domains. How such KSHV chromatin domains are maintained to be reactivatable by K-Rta remains uncle

Bivalent histone modifications are defined as repressive and activating epigenetic marks that simultaneously decorate the same genomic region. The H3K27me3 mark silences gene expression, while the H3K4me3 mark prevents the region from becoming permanently silenced and prepares the domain for activation when needed. Specific regions of Kaposi's sarcoma-associated herpesvirus (KSHV) latent episomes are poised to be activated by the KSHV replication and transcription activator (K-Rta). How KSHV episomes are prepared such that they maintain latent infection and switch to lytic replication by K-Rta remains unclear. K-Rta transactivation activity requires a protein degradation function; thus, we hypothesized that identification of cellular substrates of K-Rta may provide insight into the maintenance of KSHV latent infection and the switch to lytic replication. Here we show that a zinc finger protein, ZIC2, a key regulator for central nervous system development, is a substrate of K-Rta and is responsible for maintaining latency. K-Rta directly interacted with ZIC2 and functioned as an E3 ligase to ubiquitinate ZIC2. ZIC2 localized at immediate early and early gene cluster regions of the KSHV genome and contributed to tethering of polycomb repressive complex 2 through physical interaction, thus maintaining H3K27me3 marks at the K-Rta promoter. Accordingly, depletion of ZIC2 shifted the balance of bivalent histone modifications toward more active forms and induced KSHV reactivation in naturally infected cells. We suggest that ZIC2 turnover by K-Rta is a strategy employed by KSHV to favor the transition from latency to lytic replication.IMPORTANCE Posttranslational histone modifications regulate the accessibility of transcriptional factors to DNA; thus, they have profound effects on gene expression (e.g., viral reactivation). KSHV episomes are known to possess bivalent chromatin domains. How such KSHV chromatin domains are maintained to be reactivatable by K-Rta remains uncle

Human mutations in ZIC2 have been identified in patients with holoprosencephaly and schizophrenia. Similarly, Zic2 mutant mice exhibit holoprosencephaly in homozygosis and behavioral and morphological schizophrenic phenotypes associated with forebrain defects in heterozygosis. Despite the devastating effects of mutations in Zic2, the cellular and molecular mechanisms that provoke Zic2-deficiency phenotypes are yet unclear. Here, we report a novel role for this transcription factor in the migration of three different types of forebrain neurons: the Cajal-Retzius cells that populate the surface of the telencephalic vesicles, an amygdaloid group of cells originated in the caudal pole of the telencephalic pallium, and a cell population that travels from the prethalamic neuroepithelium to the ventral lateral geniculate nucleus. Our results also suggest that the receptor EphB1, previously identified as a Zic2 target, may mediate, at least partially, Zic2-dependent migratory events. According to these results, we propose that deficiencies in cell motility and guidance contribute to most of the forebrain pathologies associated with Zic2 mutations., [Significance statement]: Although the phenotype of Zic2 mutant individuals was reported more than 10 years ago, until now, the main function of this transcription factor during early development has not been precisely defined. Here, we reveal a previously unknown role for Zic2 in the migration of forebrain neurons such as Cajal-Retzius cells, interneurons moving to the ventral lateral geniculate nucleus, and neocortical cells going to the amygdala. We believe that the role of this transcription factor in certain populations of migratory cells contributes to defects in cortical layering and hypocellularity in the ventral LGN and amygdala and will contribute to our understanding of the devastating phenotypes associated with Zic2 mutations in both humans and mice.

Une étape initiale fondamentale dans le développement des vertébrés est l'organisation des cellules de l'embryon en trois feuillets embryonnaires primordiaux: ectoderme, mésoderme et endoderme. Chez l'embryon de xénope, le développement de l'endoderme et l’induction du mésoderme est initié par le gène maternel VegT codant pour un facteur de transcription à boîte T dont l'ARNm est localisé au pôle végétatif de l'ovocyte. Actuellement, les facteurs et mécanismes impliqués dans la formation de l'ectoderme, qui reste pluripotent jusqu'à la gastrulation, sont mal connus.Des travaux récents du laboratoire ont montré que le gène XSeb4R, codant pour une protéine de liaison à l'ARN à motif RRM, présente maternellement de manière ubiquitaire dans la blastula, interagit directement avec la région 3'UTR de l'ARNm VegT, stabilisant et stimulant sa traduction. La déplétion de XSEB4R inhibe la formation de l'endoderme et du mésoderme et sa surproduction produit l’effet inverse. Ces observations ont montré que XSeb4R joue un rôle essentiel via VegT dans la formation de l'endoderme et du mésoderme. Dans cette étude, nous avons testé l’hypothèse selon laquelle XSeb4R jouerait également un rôle au pôle animal dans la spécification de l’ectoderme. Nos résultats montrent que la protéine XSEB4R lie les régions 3’UTR des transcrits Sox3, Zic2a et Zic2b. Nous avons observé que la surexpression de XSeb4R stabilise les transcrits maternels Sox3 et Zic2 a et b, et qu’elle active la traduction des transcrits Zic2b mais pas celle de Sox3 ou Zic2a. Enfin, nous avons montré que la perte de fonction de XSeb4R induit une expansion du mésoderme vers l’ectoderme dans l’embryon au stade blastula. Ces résultats démontrent que XSeb4R joue un rôle important dans la spécification de l’ectoderme chez l’embryon de xénope., Doctorat en Sciences, info:eu-repo/semantics/nonPublished

PURPOSE: Epithelial ovarian tumors (EOT) are among the most lethal of malignancies in women. We have previously identified ZIC2 as expressed at a higher level in samples of a malignant form (MAL) of EOT than in samples of a form with low malignant potential (LMP). We have now investigated the role of ZIC2 in driving tumor growth and its association with clinical outcomes.EXPERIMENTAL DESIGN: ZIC2 expression levels were analyzed in two independent tumor tissue collections of LMP and MAL. In vitro experiments aimed to test the role of ZIC2 as a transforming gene. Cox models were used to correlate ZIC2 expression with clinical endpoints.RESULTS: ZIC2 expression was about 40-fold in terms of mRNA and about 17-fold in terms of protein in MAL (n = 193) versus LMP (n = 39) tumors. ZIC2 mRNA levels were high in MAL cell lines but undetectable in LMP cell lines. Overexpression of ZIC2 was localized to the nucleus. ZIC2 overexpression increases the growth rate and foci formation of NIH3T3 cells and stimulates anchorage-independent colony formation; downregulation of ZIC2 decreases the growth rate of MAL cell lines. Zinc finger domains 1 and 2 are required for transforming activity. In stage I MAL, ZIC2 expression was significantly associated with overall survival in both univariate (P = 0.046) and multivariate model (P = 0.049).CONCLUSIONS: ZIC2, a transcription factor related to the sonic hedgehog pathway, is a strong discriminant between MAL and LMP tumors: it may be a major determinant of outcome of EOTs. Clin Cancer Res; 18(16); 1-12. ©2012 AACR.

Holoprosencephaly is a severe malformation of the brain characterized by abnormal formation and separation of the developing central nervous system. The prevalence is 1:250 during early embryogenesis, the live-born prevalence is 1:16 000. The etiology of HPE is extremely heterogeneous and can be teratogenic or genetic. We screened four known HPE genes in a Dutch cohort of 86 non-syndromic HPE index cases, including 53 family members. We detected 21 mutations (24.4%), 3 in SHH, 9 in ZIC2 and 9 in SIX3. Eight mutations involved amino-acid substitutions, 7 ins/del mutations, 1 frame-shift, 3 identical poly-alanine tract expansions and 2 gene deletions. Pathogenicity of mutations was presumed based on de novo character, predicted non-functionality of mutated proteins, segregation of mutations with affected family-members or combinations of these features. Two mutations were reported previously. SNP array confirmed detected deletions; one spanning the ZIC2/ZIC5 genes (approx. 100 kb) the other a 1.45 Mb