Role of the Transcriptional Corepressor Bcor in Embryonic Stem Cell Differentiation and Early Embryonic Development

Bcor (BCL6 corepressor) is a widely expressed gene that is mutated in patients with X-linked Oculofaciocardiodental (OFCD) syndrome. BCOR regulates gene expression in association with a complex of proteins capable of epigenetic modification of chromatin. These include Polycomb group (PcG) proteins, Skp-Cullin-F-box (SCF) ubiquitin ligase components and a Jumonji C (Jmjc) domain containing histone demethylase. To model OFCD in mice and dissect the role of Bcor in development we have characterized two loss of function Bcor alleles. We find that Bcor loss of function results in a strong parent-of-origin effect, most likely indicating a requirement for Bcor in extraembryonic development. Using Bcor loss of function embryonic stem (ES) cells and in vitro differentiation assays, we demonstrate that Bcor plays a role in the regulation of gene expression very early in the differentiation of ES cells into ectoderm, mesoderm and downstream hematopoietic lineages. Normal expression of affected genes (Oct3/4, Nanog, Fgf5, Bmp4, Brachyury and Flk1) is restored upon re-expression of Bcor. Consistent with these ES cell results, chimeric animals generated with the same loss of function Bcor alleles show a low contribution to B and T cells and erythrocytes and have kinked and shortened tails, consistent with reduced Brachyury expression. Together these results suggest that Bcor plays a role in differentiation of multiple tissue lineages during early embryonic development

Solar Coronal Plumes

Polar plumes are thin long ray-like structures that project beyond the limb of the Sun polar regions, maintaining their identity over distances of several solar radii. Plumes have been first observed in white-light (WL) images of the Sun, but, with the advent of the space era, they have been identified also in X-ray and UV wavelengths (XUV) and, possibly, even in in situ data. This review traces the history of plumes, from the time they have been first imaged, to the complex means by which nowadays we attempt to reconstruct their 3-D structure. Spectroscopic techniques allowed us also to infer the physical parameters of plumes and estimate their electron and kinetic temperatures and their densities. However, perhaps the most interesting problem we need to solve is the role they cover in the solar wind origin and acceleration: Does the solar wind emanate from plumes or from the ambient coronal hole wherein they are embedded? Do plumes have a role in solar wind acceleration and mass loading? Answers to these questions are still somewhat ambiguous and theoretical modeling does not provide definite answers either. Recent data, with an unprecedented high spatial and temporal resolution, provide new information on the fine structure of plumes, their temporal evolution and relationship with other transient phenomena that may shed further light on these elusive features

Biodiversity of “Non-model” Rickettsiales and Their Association with Aquatic Organisms

Representatives of the order Rickettsiales are obligate intracellular bacteria, traditionally including well-studied pathogens of humans and other vertebrates, such as Rickettsia, Orientia, Anaplasma, and Ehrlichia. In the last two decades, studies based on molecular characterization techniques have reshaped our view on the biodiversity of Rickettsiales, and the eukaryotic hosts they can exploit. Several new genera have been described in “traditional” Rickettsiales families Rickettsiaceae and Anaplasmataceae. Moreover, a new family, “Candidatus Midichloriaceae,” displaying diversity at least comparable with the “traditional” ones, has been described. Recent data show that the majority of extant genera of Rickettsiales (16 out of 24) are hosted exclusively (or at least partly) by aquatic organisms, such as protists (e.g., ciliates, amoebas, flagellates), and animals (e.g., cnidarians, mollusks, tunicates, leeches), while only ten genera include some terrestrial host, such as arthropods. Given the highly interwoven phylogenetic relationships among Rickettsiales hosted by aquatic and terrestrial hosts, it is likely that the ancestral host of Rickettsiales was an aquatic protist organism, and the adaptation to terrestrial environments occurred independently in several distinct sublineages at least six times. Newly discovered lineages of “non-model” Rickettsiales present unforeseen features for the order such as the presence of flagella. Future investigations on “non-model” Rickettsiales are crucial to gain insight on the evolutionary history of the whole group, including the origin of molecular mechanisms involved in pathogenesis for humans and vertebrates