Mitotic spindle scaling during Xenopus development by kif2a and importin α.

Early development of many animals is characterized by rapid cleavages that dramatically decrease cell size, but how the mitotic spindle adapts to changing cell dimensions is not understood. To identify mechanisms that scale the spindle during Xenopus laevis embryogenesis, we established an in vitro system using cytoplasmic extracts prepared from embryos that recapitulates in vivo spindle size differences between stage 3 (4 cells, 37 µm) and stage 8 (∼4000 cells, 18 µm). We identified the kinesin-13 kif2a as a driver of developmental spindle scaling whose microtubule-destabilizing activity is inhibited in stage 3 spindles by the transport receptor importin α, and activated in stage 8 when importin α partitions to a membrane pool. Altering spindle size in developing embryos impaired spindle orientation during metaphase, but chromosome segregation remained robust. Thus, spindle size in Xenopus development is coupled to cell size through a ratiometric mechanism controlling microtubule destabilization.DOI:http://dx.doi.org/10.7554/eLife.00290.001

Un modelo del gasto con factores sociodemográficos y de hábitos de viaje en Pueblos Mágicos del Estado de Guanajuato, México

En este trabajo se presenta un panorama de la industria turística mexicana que incluye un análisis de las tendencias y la competitividad del sector en el contexto de la aplicación del Programa Nacional de Pueblos Mágicos. Se desarrolla un modelo econométrico con el fin de analizar el comportamiento del gasto de los visitantes a los Pueblos Mágicos del Estado de Guanajuato. Los coeficientes del modelo son estimados con una base de datos de la Secretaría de Turismo del Estado de Guanajuato. La información se generó a partir de una encuesta aplicada en los cinco Pueblos Mágicos de esa entidad en el año 2013. El modelo permite estimar elasticidades de los factores de impacto y generar niveles de referencia de gasto en diferentes escenarios. El modelo se plantea como una regresión log-lineal con variables explicativas que capturan características sociodemográficas y de hábitos de viaje. Tomando en cuenta los resultados del modelo, se discuten estrategias para estimular el crecimiento de la demanda turística en estos Pueblos Mágicos.This paper provides a general vision of the tourism industry in Mexico with an analysis of its overall trends and competitiveness with especial emphasis in the Pueblos Magicos National Programme. An econometric analysis has been carried out in order to analyze the expenditure patters of visitors to the Pueblos Magicos of Guanajuato State. The expenditure model coefficients are calculated using a data base of the Secretaria de Turismo de Guanajuato – SECTUR-GTO (Guanajuato Tourist Office). The data base was created from a survey questionnaire administered to the five Pueblos Magicos of the State in 2013. The model enables the computation of expenditure elasticities for the impact factors and the generation of reference expenditures under different scenarios. The model is a log-linear regression with explicative variables that capture socio demographic characteristics and travel habits. The results are used in order to discuss strategies for stimulating tourist demand growth in these Pueblos Magicos

A Network of two Markets, Correlations for Stocks in the S&P500 Index and Stocks Traded in the BMV

Una Red entre dos mercados, correlaciones entre acciones en el Índice S&P500 y acciones comercializadas en BMVNuestro objetivo es estudiar como las acciones de México y Estados Unidos están interconectadas. Aplicamos un método novedoso basado en un modelo gráfico. Estimamos correlaciones parciales para cada año del período 2000-2020. Nuestros resultados basados en matrices de correlaciones parciales muestran un nivel sistemático de interconectividad entre países que métricas de la teoría de redes confirman. Una diferencia importante entre estos países es como los sectores en cada mercado se enlazan. La mayoría de los sectores en los Estados Unidos están densamente interconectados. En contraste, sectores en México presentan menos enlaces. Después comparamos redes en los períodos de la crisis hipotecaria subprime y la crisis originada por la pandemia COVID-19. Las diferentes velocidades de propagación de ambas crisis son correctamente capturadas por las métricas. Una limitación surge de la información y es deseable incluir datos actualizados. El novedoso método utilizado, que llevó a obtener nuevos resultados, dota de originalidad al trabajo. Se concluye que datos desagregados son una dirección de investigación prometedora.Our goal is to study how stocks from Mexico and United States are interconnected. We apply a novel method based on a graphical model. We estimate partial correlations for every year of the period 2000-2020. Our results based on partial correlation matrices show a systematic level of inter-connectivity across countries that metrics from network theory confirm. An important difference between these countries is how sectors in each market are linked. Most sector graphs in the United States are densely interconnected. In contrast, sectors in Mexico present much less links. We then compare networks in the periods of the subprime mortgage crisis and the crisis triggered by the COVID-19 pandemic. The different propagation speeds of both crises are correctly captured by the metrics. A limitation is derived from information, and it is desirable to include actualized data in the study. The deployed novel method, which led to obtain new results, endow originality to the work. It is concluded that disaggregated data provides a promising venue of research

Synergy between multiple microtubule-generating pathways confers robustness to centrosome-driven mitotic spindle formation.

notes: PMCID: PMC3898610types: Journal Article; Research Support, Non-U.S. Gov'tCopyright © 2014 The Authors. Published by Elsevier Inc. All rights reserved.The mitotic spindle is defined by its organized, bipolar mass of microtubules, which drive chromosome alignment and segregation. Although different cells have been shown to use different molecular pathways to generate the microtubules required for spindle formation, how these pathways are coordinated within a single cell is poorly understood. We have tested the limits within which the Drosophila embryonic spindle forms, disrupting the inherent temporal control that overlays mitotic microtubule generation, interfering with the molecular mechanism that generates new microtubules from preexisting ones, and disrupting the spatial relationship between microtubule nucleation and the usually dominant centrosome. Our work uncovers the possible routes to spindle formation in embryos and establishes the central role of Augmin in all microtubule-generating pathways. It also demonstrates that the contributions of each pathway to spindle formation are integrated, highlighting the remarkable flexibility with which cells can respond to perturbations that limit their capacity to generate microtubules.Biotechnology and Biological Sciences Research Council PhD studentship (to D.H.)Wellcome Trust Institutional Strategic Support Fund WT097835MF (to J.G.W. and J.M.)

Viral Mimicry of Cdc2/Cyclin-Dependent Kinase 1 Mediates Disruption of Nuclear Lamina during Human Cytomegalovirus Nuclear Egress

The nuclear lamina is a major obstacle encountered by herpesvirus nucleocapsids in their passage from the nucleus to the cytoplasm (nuclear egress). We found that the human cytomegalovirus (HCMV)-encoded protein kinase UL97, which is required for efficient nuclear egress, phosphorylates the nuclear lamina component lamin A/C in vitro on sites targeted by Cdc2/cyclin-dependent kinase 1, the enzyme that is responsible for breaking down the nuclear lamina during mitosis. Quantitative mass spectrometry analyses, comparing lamin A/C isolated from cells infected with viruses either expressing or lacking UL97 activity, revealed UL97-dependent phosphorylation of lamin A/C on the serine at residue 22 (Ser22). Transient treatment of HCMV-infected cells with maribavir, an inhibitor of UL97 kinase activity, reduced lamin A/C phosphorylation by approximately 50%, consistent with UL97 directly phosphorylating lamin A/C during HCMV replication. Phosphorylation of lamin A/C during viral replication was accompanied by changes in the shape of the nucleus, as well as thinning, invaginations, and discrete breaks in the nuclear lamina, all of which required UL97 activity. As Ser22 is a phosphorylation site of particularly strong relevance for lamin A/C disassembly, our data support a model wherein viral mimicry of a mitotic host cell kinase activity promotes nuclear egress while accommodating viral arrest of the cell cycle

Genome evolution in the allotetraploid frog Xenopus laevis

To explore the origins and consequences of tetraploidy in the African clawed frog, we sequenced the Xenopus laevis genome and compared it to the related diploid X. tropicalis genome. We characterize the allotetraploid origin of X. laevis by partitioning its genome into two homoeologous subgenomes, marked by distinct families of ???fossil??? transposable elements. On the basis of the activity of these elements and the age of hundreds of unitary pseudogenes, we estimate that the two diploid progenitor species diverged around 34 million years ago (Ma) and combined to form an allotetraploid around 17-18 Ma. More than 56% of all genes were retained in two homoeologous copies. Protein function, gene expression, and the amount of conserved flanking sequence all correlate with retention rates. The subgenomes have evolved asymmetrically, with one chromosome set more often preserving the ancestral state and the other experiencing more gene loss, deletion, rearrangement, and reduced gene expression.ope

Decentralized rural development and poverty reduction in Mexico : is "solidarity economy" the answer?

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