Microarray analysis of Foxa2 mutant mouse embryos reveals novel gene expression and inductive roles for the gastrula organizer and its derivatives

<p>Abstract</p> <p>Background</p> <p>The Spemann/Mangold organizer is a transient tissue critical for patterning the gastrula stage vertebrate embryo and formation of the three germ layers. Despite its important role during development, there are still relatively few genes with specific expression in the organizer and its derivatives. Foxa2 is a forkhead transcription factor that is absolutely required for formation of the mammalian equivalent of the organizer, the node, the axial mesoderm and the definitive endoderm (DE). However, the targets of Foxa2 during embryogenesis, and the molecular impact of organizer loss on the gastrula embryo, have not been well defined.</p> <p>Results</p> <p>To identify genes specific to the Spemann/Mangold organizer, we performed a microarray-based screen that compared wild-type and <it>Foxa2 </it>mutant embryos at late gastrulation stage (E7.5). We could detect genes that were consistently down-regulated in replicate pools of mutant embryos versus wild-type, and these included a number of known node and DE markers. We selected 314 genes without previously published data at E7.5 and screened for expression by whole mount <it>in situ </it>hybridization. We identified 10 novel expression patterns in the node and 5 in the definitive endoderm. We also found significant reduction of markers expressed in secondary tissues that require interaction with the organizer and its derivatives, such as cardiac mesoderm, vasculature, primitive streak, and anterior neuroectoderm.</p> <p>Conclusion</p> <p>The genes identified in this screen represent novel Spemann/Mangold organizer genes as well as potential Foxa2 targets. Further investigation will be needed to define these genes as novel developmental regulatory factors involved in organizer formation and function. We have placed these genes in a Foxa2-dependent genetic regulatory network and we hypothesize how Foxa2 may regulate a molecular program of Spemann/Mangold organizer development. We have also shown how early loss of the organizer and its inductive properties in an otherwise normal embryo, impacts on the molecular profile of surrounding tissues.</p

The ice-breaker effect: Singing mediates fast social bonding

It has been proposed that singing evolved to facilitate social cohesion. However, it remains unclear whether bonding arises out of properties intrinsic to singing or whether any social engagement can have a similar effect. Furthermore, previous research has used one-off singing sessions without exploring the emergence of social bonding over time. In this semi-naturalistic study, we followed newly formed singing and non-singing (crafts or creative writing) adult education classes over seven months. Participants rated their closeness to their group and their affect, and were given a proxy measure of endorphin release, before and after their class, at three timepoints (months 1, 3 and 7). We show that although singers and non-singers felt equally connected by timepoint 3, singers experienced much faster bonding: singers demonstrated a significantly greater increase in closeness at timepoint 1, but the more gradual increase shown by non-singers caught up over time. This represents the first evidence for an ‘ice-breaker effect’ of singing in promoting fast cohesion between unfamiliar individuals, which bypasses the need for personal knowledge of group members gained through prolonged interaction. We argue that singing may have evolved to quickly bond large human groups of relative strangers, potentially through encouraging willingness to coordinate by enhancing positive affect

Atlantic Salmon (Salmo salar L.) Gastrointestinal Microbial Community Dynamics in Relation to Digesta Properties and Diet

To better understand salmon GI tract microbial community dynamics in relation to diet, a feeding trial was performed utilising diets with different proportions of fish meal, protein, lipid and energy levels. Salmon gut dysfunction has been associated with the occurrence of casts, or an empty hind gut. A categorical scoring system describing expressed digesta consistency was evaluated in relation to GI tract community structure. Faster growing fish generally had lower faecal scores while the diet cohorts showed minor differences in faecal score though the overall lowest scores were observed with a low protein, low energy diet. The GI tract bacterial communities were highly dynamic over time with the low protein, low energy diet associated with the most divergent community structure. This included transiently increased abundance of anaerobic (Bacteroidia and Clostridia) during January and February, and facultatively anaerobic (lactic acid bacteria) taxa from February onwards. The digesta had enriched populations of these groups in relation to faecal cast samples. The majority of samples (60&ndash;86&nbsp;%) across all diet cohorts were eventually dominated by the genus Aliivibrio. The results suggest that an interaction between time of sampling and diet is most strongly related to community structure. Digesta categorization revealed microbes involved with metabolism of diet components change progressively over time and could be a useful system to assess feeding responses.&nbsp

In vitro characteristics of an Atlantic salmon (Salmo salar L.) hind gut microbial community in relation to different dietary treatments

In this study, microbial community dynamics were assessed within a simple invitro model system in order to understand those changes influenced by diet. The abundance and diversity of bacteria were monitored within different treatment slurries inoculated with salmon faecal samples in order to mimic the effects of dietary variables. A total of five complete diets and two ingredients (plant meal) were tested. The total viable counts (TVCs) and sequencing data revealed that there was very clear separation between the complete diets and the plant meal treatments, suggesting a dynamic response by the allochthonous bacteria to the treatments. Automated ribosomal intergenic spacer analysis (ARISA) results showed that different diet formulations produced different patterns of fragments, with no separation between the complete diets. However, plant-based protein ingredients were clearly separated from the other treatments. 16S rRNA Illumina-based sequencing analysis showed that members of the genera Aliivibrio,Vibrio&nbsp;and Photobacterium&nbsp;became predominant for all complete diets treatments. The plant-based protein ingredient treatments only sustained weak growth of the genusSphingomonas. Invitro based testing of diets could be a useful strategy to determine the potential impact of either complete feeds or ingredients on major fish gastrointestinal tract microbiome members

Elevation and cholera: an epidemiological spatial analysis of the cholera epidemic in Harare, Zimbabwe, 2008-2009

BACKGROUND: In highly populated African urban areas where access to clean water is a challenge, water source contamination is one of the most cited risk factors in a cholera epidemic. During the rainy season, where there is either no sewage disposal or working sewer system, runoff of rains follows the slopes and gets into the lower parts of towns where shallow wells could easily become contaminated by excretes. In cholera endemic areas, spatial information about topographical elevation could help to guide preventive interventions. This study aims to analyze the association between topographic elevation and the distribution of cholera cases in Harare during the cholera epidemic in 2008 and 2009. METHODS: We developed an ecological study using secondary data. First, we described attack rates by suburb and then calculated rate ratios using whole Harare as reference. We illustrated the average elevation and cholera cases by suburbs using geographical information. Finally, we estimated a generalized linear mixed model (under the assumption of a Poisson distribution) with an Empirical Bayesian approach to model the relation between the risk of cholera and the elevation in meters in Harare. We used a random intercept to allow for spatial correlation of neighboring suburbs. RESULTS: This study identifies a spatial pattern of the distribution of cholera cases in the Harare epidemic, characterized by a lower cholera risk in the highest elevation suburbs of Harare. The generalized linear mixed model showed that for each 100 meters of increase in the topographical elevation, the cholera risk was 30% lower with a rate ratio of 0.70 (95% confidence interval=0.66-0.76). Sensitivity analysis confirmed the risk reduction with an overall estimate of the rate ratio between 20% and 40%. CONCLUSION: This study highlights the importance of considering topographical elevation as a geographical and environmental risk factor in order to plan cholera preventive activities linked with water and sanitation in endemic areas. Furthermore, elevation information, among other risk factors, could help to spatially orientate cholera control interventions during an epidemic

Teleost Growth Factor Independence (Gfi) Genes Differentially Regulate Successive Waves of Hematopoiesis

Growth Factor Independence (Gfi) transcription factors play essential roles in hematopoiesis, differentially activating and repressing transcriptional programs required for hematopoietic stem/progenitor cell (HSPC) development and lineage specification. In mammals, Gfi1a regulates hematopoietic stem cells (HSC), myeloid and lymphoid populations, while its paralog, Gfi1b, regulates HSC, megakaryocyte and erythroid development. In zebrafish, gfi1aa is essential for primitive hematopoiesis; however, little is known about the role of gfi1aa in definitive hematopoiesis or about additional gfi factors in zebrafish. Here, we report the isolation and characterization of an additional hematopoietic gfi factor, gfi1b. We show that gfi1aa and gfi1b are expressed in the primitive and definitive sites of hematopoiesis in zebrafish. Our functional analyses demonstrate that gfi1aa and gfi1b have distinct roles in regulating primitive and definitive hematopoietic progenitors, respectively. Loss of gfi1aa silences markers of early primitive progenitors, scl and gata1. Conversely, loss of gfi1b silences runx-1, c-myb, ikaros and cd41, indicating that gfi1b is required for definitive hematopoiesis. We determine the epistatic relationships between the gfi factors and key hematopoietic transcription factors, demonstrating that gfi1aa and gfi1b join lmo2, scl, runx-1 and c-myb as critical regulators of teleost HSPC. Our studies establish a comparative paradigm for the regulation of hematopoietic lineages by gfi transcription factors.Stem Cell and Regenerative Biolog

Zfp206 regulates ES cell gene expression and differentiation

Understanding transcriptional regulation in early developmental stages is fundamental to understanding mammalian development and embryonic stem (ES) cell properties. Expression surveys suggest that the putative SCAN-Zinc finger transcription factor Zfp206 is expressed specifically in ES cells [Zhang,W., Morris,Q.D., Chang,R., Shai,O., Bakowski,M.A., Mitsakakis,N., Mohammad,N., Robinson,M.D., Zirngibl,R., Somogyi,E. et al., (2004) J. Biol., 3, 21; Brandenberger,R., Wei,H., Zhang,S., Lei,S., Murage,J., Fisk,G.J., Li,Y., Xu,C., Fang,R., Guegler,K. et al., (2004) Nat. Biotechnol., 22, 707–716]. Here, we confirm this observation, and we show that ZFP206 expression decreases rapidly upon differentiation of cultured mouse ES cells, and during development of mouse embryos. We find that there are at least six isoforms of the ZFP206 transcript, the longest being predominant. Overexpression and depletion experiments show that Zfp206 promotes formation of undifferentiated ES cell clones, and positively regulates abundance of a very small set of transcripts whose expression is also specific to ES cells and the two- to four-cell stages of preimplantation embryos. This set includes members of the Zscan4, Thoc4, Tcstv1 and eIF-1A gene families, none of which have been functionally characterized in vivo but whose members include apparent transcription factors, RNA-binding proteins and translation factors. Together, these data indicate that Zfp206 is a regulator of ES cell differentiation that controls a set of genes expressed very early in development, most of which themselves appear to be regulators