Early Loss of Xist RNA Expression and Inactive X Chromosome Associated Chromatin Modification in Developing Primordial Germ Cells

The inactive X chromosome characteristic of female somatic lineages is reactivated during development of the female germ cell lineage. In mouse, analysis of protein products of X-linked genes and/or transgenes located on the X chromosome has indicated that reactivation occurs after primordial germ cells reach the genital ridges.We present evidence that the epigenetic reprogramming of the inactive X-chromosome is initiated earlier than was previously thought, around the time that primordial germ cells (PGCs) migrate through the hindgut. Specifically, we find that Xist RNA expression, the primary signal for establishment of chromosome silencing, is extinguished in migrating PGCs. This is accompanied by displacement of Polycomb-group repressor proteins Eed and Suz(12), and loss of the inactive X associated histone modification, methylation of histone H3 lysine 27.We conclude that X reactivation in primordial germ cells occurs progressively, initiated by extinction of Xist RNA around the time that germ cells migrate through the hindgut to the genital ridges. The events that we observe are reminiscent of X reactivation of the paternal X chromosome in inner cell mass cells of mouse pre-implantation embryos and suggest a unified model in which execution of the pluripotency program represses Xist RNA thereby triggering progressive reversal of epigenetic silencing of the X chromosome

Pathogens, parasites, and parasitoids associated with bumble bees (Bombus spp.) from Uruguay

As elsewhere in the world, bumble bees play a vital role as pollinators in Uruguay, but knowledge on their health status is still limited. Between September 2012 and May 2013, 403 adult individuals of the two speciesof Bombus known for the country (Bombus atratus , Bombus bellicosus ) were collected in six localities.We found that 177 (119 B. atratus, 58 B. bellicosus ) were harboring one or two types of pathogens, parasites, or parasitoids.Identification of these natural enemies carried out by morphological or molecular procedures revealed the presence of two species of Microsporidia [Nosema ceranae (prevalence: 18.2 % in B. atratus; 44.9 % in B. bellicosus ),Tubulinosema pampeana (prevalence: 13 % in B. atratus )], two species of Nematoda [Sphaerularia bombi (prevalence: 40.4 % in B. atratus; 40% in B. bellicosus ) and an unidentified Mermithidae (prevalence: 0.8 % inB. bellicosus )], and one species of Diptera parasitoid (prevalence: 3.2 % in B. atratus ; 4.2 % in B. bellicosus ). Except N. ceranae , none of the other species have been previously reported in Uruguay.Fil: Plischuk, Santiago. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Centro de Estudios Parasitológicos y de Vectores. Universidad Nacional de La Plata. Facultad de Ciencias Naturales y Museo. Centro de Estudios Parasitológicos y de Vectores; ArgentinaFil: Salvarrey, Sheena. Universidad de la República. Facultad de Ciencias; UruguayFil: Arbulo, Natalia. Universidad de la República; UruguayFil: Santos, Estela. Universidad de la República. Facultad de Ciencias; UruguayFil: Skevington, Jeffrey H.. Canadian National Collection of Insects; CanadáFil: Kelso, Scott. Canadian National Collection of Insects; CanadáFil: Revainera, Pablo Damian. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mar del Plata; Argentina. Universidad Nacional de Mar del Plata; ArgentinaFil: Maggi, Matías Daniel. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mar del Plata; Argentina. Universidad Nacional de Mar del Plata; ArgentinaFil: Invernizzi, Ciro. Universidad de la República. Facultad de Ciencias; UruguayFil: Lange, Carlos Ernesto. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Centro de Estudios Parasitológicos y de Vectores. Universidad Nacional de La Plata. Facultad de Ciencias Naturales y Museo. Centro de Estudios Parasitológicos y de Vectores; Argentina. Provincia de Buenos Aires. Gobernación. Comisión de Investigaciones Científicas; Argentin

Europe-wide reassessment of Dictyocoela (Microsporidia) infecting native and invasive amphipods (Crustacea): molecular versus ultrastructural traits.

16 pagesInternational audienceMicrosporidia are common parasites infecting animals and protists. They are specifically common pathogens of amphipods (Crustacea, Malacostraca), with Dictyocoela spp. being particularly frequent and highly prevalent, exhibiting a range of phenotypic and ecological effects. Until now, seven species of Dictyocoela were defined, predominantly based on the genetic distance. However, neither the taxonomic status of this provisionally erected genus (based on eight novel sequences and one micrograph of the spore), nor its internal phylogenetic relationships have been clearly revealed. The formal description of the genus and of most of the putative species are still lacking. Here we aimed to fill this gap and performed both ultrastructural and molecular studies (based on SSU, ITS and partial LSU) using different species delimitation methods. As a consensus of these results and following conservative data interpretation, we propose to distinguish five species infecting gammarid hosts, and to keep the names introduced by the authors of the type sequences: Dictyocoela duebenum, D. muelleri, D. berillonum and D. roeselum. We provide full descriptions of these species. Moreover, thanks to our extensive sampling, we extend the known host and geographic range of these Microsporidia

Derivation of human embryonic stem cells using a post-inner cell mass intermediate

Little is known about the true developmental origin of human embryonic stem cells (hESCESCESCs) or the events that initiate their generation. Recently, we have shown that hESCESCESCs originate from a post–inner cell mass (ICM) intermediate (PICMI), a unique transient epiblast-like structure that is different from both its ICM progenitor and its subsequent hESCESCESC fate. As a closer progenitor of hESCESCESCs than the ICM, the PICMI could be used to provide further insight into the human pluripotent state. Here we provide a detailed (7-d) protocol for the culture of the human preimplantation embryos in order to derive the PICMI. Subsequent identification and cryopreservation of the PICMI are described, in addition to hESCESCESC derivation. The initial hESCESCESC outgrowth is visible within 2–7 d after PICMI plating. By using the protocol provided, we observed PICMI formation in 21.3% of plated blastocysts with good-quality ICMs. Of the PICMIs used for hESCESCESC derivation, 80.6% showed hESCESCESC outgrowth after further culture