Differential requirements for Tousled-like kinases 1 and 2 in mammalian development

The regulation of chromatin structure is critical for a wide range of essential cellular processes. The Tousled-like kinases, TLK1 and TLK2, regulate ASF1, a histone H3/H4 chaperone, and likely other substrates, and their activity has been implicated in transcription, DNA replication, DNA repair, RNA interference, cell cycle progression, viral latency, chromosome segregation and mitosis. However, little is known about the functions of TLK activity in vivo or the relative functions of the highly similar TLK1 and TLK2 in any cell type. To begin to address this, we have generated Tlk1- and Tlk2-deficient mice. We found that while TLK1 was dispensable for murine viability, TLK2 loss led to late embryonic lethality because of placental failure. TLK2 was required for normal trophoblast differentiation and the phosphorylation of ASF1 was reduced in placentas lacking TLK2. Conditional bypass of the placental phenotype allowed the generation of apparently healthy Tlk2-deficient mice, while only the depletion of both TLK1 and TLK2 led to extensive genomic instability, indicating that both activities contribute to genome maintenance. Our data identifies a specific role for TLK2 in placental function during mammalian development and suggests that TLK1 and TLK2 have largely redundant roles in genome maintenance

Morfologia e anatomia das domácias em Coffea arabica L.

1. A presente contribuição trata do estudo morfológico e anatômico das domácias que ocorrem em 21 variedades e 4 formas da espécie Coffea arabica L. 2. Além da revisão da literatura, que se cingiu unicamente aos trabalhos que focalizam o assunto em aprêço, constam, na introdução, algumas obras que se referem às domácias existentes em outras famílias. 3. A fim de apreciar convenientemente os conceitos que os diferentes autores expediram a respeito das domácias, desde que se tornaram conhecidas, foram registradas, no capítulo correspondente, as funções e as diversas denominações que lhes foram atribuidas. 4. As principais classificações das domácias propostas são de CHEVALIER, LEBRUM e DE WILDEMAN. As domácias das variedades e formas de Coffea arabica L., se enquadram no tipo b, isto é, domácias em fenda, segundo a classificação de CHEVALIER. 5. O material utilizado no presente estudo, constante de ramos com fôlhas de várias idades, proveio do Instituto Agronômico de Campinas e da Secção de Agricultura Especial da E.S.A. "Luiz de Queiroz". As observações morfológicas das domácias foram feitas com o auxílio do microscópio estereoscópico e constam do Quadro I e II. A estrutura anatômica foi apreciada em cortes transversais medianos da domácia, coloridos pelo violeta cristal e eritrosina, com espessura de 18 micra, cujos dados acham-se anotados nos Quadros de n.os III a XI. 6. No capítulo referente à morfologia e à anatomia das domácias, para melhor apreciação do assunto foi introduzida a estrutura anatômica da fôlha adulta da variedade typica. 7. Morfològicamente as domácias foram examinadas nas suas duas faces, isto é, superior e inferior, anotando-se-lhes os aspectos apresentados, bem como a sua localização no limbo, isto é, na axila formada pelas nervuras principal e secundárias. No geral a sua distribuição vai desde a base do limbo até aos 2/3, aproximadamente, do seu comprimento. Na face ventral da fôlha, as domácias exibem uma elevação abaulada e na dorsal situam-se na área da axila, e em um plano um pouco mais elevado que o limbo, mostrando no centro um orifício de forma variável. Em cortes medianos, a domácia revela-se constituida de uma câmara embutida no mesofilo, a qual se comunica com o exterior por um canal; êste por sua vez, termina numa bôca que se abre na epiderme inferior do limbo. Histològicamente a domácia consta de uma epiderme, procedente do limbo e da nervura, e de um tecido parênquimatoso envolvente, composto de algumas camadas de células, o qual confina com os tecidos do mesofilo. Topogràficamente a domácia situa-se entre os seguintes tecidos da estrutura foliar: sistema vascular principal, nervura secundária, parênquima lacunoso lateral e parênquima lacunoso superior. Sua posição com relação às regiões mencionadas fica perfeitamente definida, determinando-se as distâncias que vão do centro da câmara até elas.The morphology and anatomy of domatia structures of 21 varieties and 4 strains of coffee plants (Coffea arabica L.) were studied and the resultas may be summarized as follows: 1. All the domatia structures observed belongs to type b of CHEVALIER. 2. In all coffee plants studied the domatia structures have the same tópographic position: close to the primary vein, between this and the secondary veins. 3. In each leaf the domatiae are distributed from the base up to 2/3 of the midrib length. 4. Differences in structure occur among the epidermis that lined the mouth opening, channel and chamber. No stomata were found here. 5. Te morphological and anatomical variations found in the domatia structures are not enough to distinguish apart the several coffee plant varietis studied

Retinoic acid induces TGFbeta-dependent autocrine fibroblast growth.

peer reviewedaudience: researcherTo evaluate the role of murine TFIID subunit TAF4 in activation of cellular genes by all-trans retinoic acid (T-RA), we have characterized the T-RA response of taf4(lox/-) and taf4(-/-) embryonic fibroblasts. T-RA regulates almost 1000 genes in taf4(lox/-) cells, but less than 300 in taf4(-/-) cells showing that TAF4 is required for T-RA regulation of most, but not all cellular genes. We further show that T-RA-treated taf4(lox/-) cells exhibit transforming growth factor (TGF)beta-dependent autocrine growth and identify a set of genes regulated by loss of TAF4 and by T-RA corresponding to key mediators of the TGFbeta signalling pathway. T-RA rapidly and potently induces expression of connective tissue growth factor (CTGF) via a conserved DR2 type response element in its proximal promoter leading to serum-free autocrine growth. These results highlight the role of TAF4 as a cofactor in the cellular response to T-RA and identify the genetic programme of a novel cross talk between the T-RA and TGFbeta pathways that leads to deregulated cell growth

Institutional dimensions and entrepreneurial activity: An international study

The purpose of this article is to examine the influence of institutional dimensions (regulative, normative and cultural-cognitive) on the probability of becoming an entrepreneur. The main findings demonstrate, through logistic regression, that a favourable regulative dimension (fewer procedures to start a business), normative dimension (higher media attention for new business) and cultural-cognitive dimension (better entrepreneurial skills, less fear of business failure and better knowing of entrepreneurs) increase the probability of being an entrepreneur. Data were obtained from both the Global Entrepreneurship Monitor and the International Institute for Management and Development for the year 2008, considering a sample of 30 countries and 36,525 individuals. The study advances the literature by providing new information on the environmental factors that affect entrepreneurial activity in the light of institutional economics. Also, the research could be useful for designing policies to foster entrepreneurship in different environments. © 2013 Springer Science+Business Media New York

What Makes and What Does Not Make a Real Option? A Study of International Joint Ventures

This paper examines the boundaries of real options logic, with an application to joint ventures (JVs). We distinguish between forms of uncertainty that are resolved endogenously and those that are resolved exogenously, and theorize that only exogenous uncertainty will have the impact predicted by real options theory on a foreign investor's choice of how large an equity share to take in a JV. We theorize that macroeconomic and institutional variables generate exogenous uncertainty whereas, by contrast, cultural distance and choices pertaining to corporate scope and product or process development activities involve endogenous sources of uncertainty that investors can both assess and act upon without having to “wait and see”. Using a sample of 6472 Sino-foreign JVs, we find support for our predictions. We discuss and implement proper methods to test for the existence of null effects, as is relevant to establish the boundaries of a theory such as real options theory. We draw implications for research and practice on JVs – specifically equity share decisions, which deserve more attention – and real options, including suitable uses and desirable extensions of the concept