Gata2 in Hematopoietic Cell Generation

The mammalian hematopoietic system is maintained by hematopoietic stem cells (HSC). Whereas in the adult, they reside in the bone marrow, the first HSCs are generated in the main vasculature of the midgestation embryo as a result of tightly regulated extrinsic and intrinsic molecular signals. Transcriptional regulation is pivotal to the establishment of HSC fate during development and the Gata2 transcription factor is central to this process. Genetic deletion of Gata2 shows that it is essential for the embryonic generation of HSCs, hematopoietic progenitor cells (HPC), and also for the establishment of some mature blood lineages, such as mast cells. Although previous studies with HPC/HSC enriched populations indicate the importance of Gata2 in their generation, there has been no direct way for studying Gata2-expressing cells in normal embryonic development, and in in vitro hematopoietic differentiation assays. In this thesis research, I use a novel Gata2Venus reporter embryonic stem cell (ESC) system and mouse model to dissect the role of Gata2 in hematopoietic differentiation and development. I show that Venus expression discriminates progressive stages of hematopoietic cell generation in vitro that are highly analogous to the in vivo waves of hematopoietic cell generation. My results demonstrate the involvement of the Gata2 downstream target, Gpr56 (a putative HSC regulator), in the development of HPCs, and reveal the redundant expression and function of Gpr56 with another G-protein coupled receptor, Gpr97. This redundancy may explain the previous contradictory data in the field regarding the requirement for Gpr56 in HSCs, and opens the way for new strategies to delineate the role of Gpr56 in HSC emergence. In addition to HSCs and HPCs, the mast cell lineage is one of the few mature blood cell types that expresses Gata2. Taking advantage of the Gata2Venus ESC reporter line and human induced pluripotent stem cell (iPSC) lines, I found a novel and powerful approach to rapidly generate mast cells for inflammation and allergy research applications. This thesis research has furthered our understanding of the role of Gata2 in in vivo embryonic development, and in in vitro pluripotent stem cell hematopoietic differentiation approaches, providing the basis for the development of future therapeutic strategies in blood and inflammation research

Workplace bullying and violence as risk factors for type 2 diabetes : a multicohort study and meta-analysis

The aim of this multicohort study was to examine whether employees exposed to social stressors at work, such as workplace bullying and violence, have an increased risk of type 2 diabetes. The study included 45,905 men and women (40-65 years of age and free of diabetes at baseline) from four studies in Sweden, Denmark and Finland. Workplace bullying and violence were self-reported at baseline. Incident diabetes was ascertained through national health and medication records and death registers. Marginal structural Cox models adjusted for age, sex, country of birth, marital status and educational level were used for the analyses. Nine per cent of the population reported being bullied at work and 12% were exposed to workplace violence or threats of violence. Bullied participants had a 1.46 (95% CI 1.23, 1.74) times higher risk of developing diabetes compared with non-bullied participants. Exposure to violence or threats of violence was also associated with a higher risk of diabetes (HR 1.26 [95% CI 1.02, 1.56]). The risk estimates attenuated slightly when taking BMI into account, especially for bullying. The results were similar for men and women, and were consistent across cohorts. We found a higher risk of incident type 2 diabetes among employees exposed to bullying or violence in the workplace. Further research is needed to determine whether policies to reduce bullying and violence at work may reduce the incidence of type 2 diabetes in working populations. Research on the mechanisms is also highly warranted.Peer reviewe

Workplace bullying and workplace violence as risk factors for cardiovascular disease : a multi-cohort study

Aims To assess the associations between bullying and violence at work and cardiovascular disease (CVD). Methods and results Participants were 79201 working men and women, aged 18-65years and free of CVD and were sourced from three cohort studies from Sweden and Denmark. Exposure to workplace bullying and violence was measured at baseline using self-reports. Participants were linked to nationwide health and death registers to ascertain incident CVD, including coronary heart disease and cerebrovascular disease. Study-specific results were estimated by marginal structural Cox regression and were combined using fixed-effect meta-analysis. Nine percent reported being bullied at work and 13% recorded exposure to workplace violence during the past year. We recorded 3229 incident CVD cases with a mean follow-up of 12.4years (765 in the first 4years). After adjustment for age, sex, country of birth, marital status, and educational level, being bullied at work vs. not was associated with a hazard ratio (HR) of 1.59 [95% confidence interval (CI) 1.28-1.98] for CVD. Experiencing workplace violence vs. not was associated with a HR of 1.25 (95% CI 1.12-1.40) for CVD. The population attributable risk was 5.0% for workplace bullying and 3.1% for workplace violence. The excess risk remained similar in analyses with different follow-up lengths, cardiovascular risk stratifications, and after additional adjustments. Dose-response relations were observed for both workplace bullying and violence (P-trend <0.001). There was only negligible heterogeneity in study-specific estimates. Conclusion Bullying and violence are common at workplaces and those exposed to these stressors are at higher risk of CVD.Peer reviewe

Hundreds of variants clustered in genomic loci and biological pathways affect human height

Most common human traits and diseases have a polygenic pattern of inheritance: DNA sequence variants at many genetic loci influence the phenotype. Genome-wide association (GWA) studies have identified more than 600 variants associated with human traits, but these typically explain small fractions of phenotypic variation, raising questions about the use of further studies. Here, using 183,727 individuals, we show that hundreds of genetic variants, in at least 180 loci, influence adult height, a highly heritable and classic polygenic trait. The large number of loci reveals patterns with important implications for genetic studies of common human diseases and traits. First, the 180 loci are not random, but instead are enriched for genes that are connected in biological pathways (P = 0.016) and that underlie skeletal growth defects (P < 0.001). Second, the likely causal gene is often located near the most strongly associated variant: in 13 of 21 loci containing a known skeletal growth gene, that gene was closest to the associated variant. Third, at least 19 loci have multiple independently associated variants, suggesting that allelic heterogeneity is a frequent feature of polygenic traits, that comprehensive explorations of already-discovered loci should discover additional variants and that an appreciable fraction of associated loci may have been identified. Fourth, associated variants are enriched for likely functional effects on genes, being over-represented among variants that alter amino-acid structure of proteins and expression levels of nearby genes. Our data explain approximately 10% of the phenotypic variation in height, and we estimate that unidentified common variants of similar effect sizes would increase this figure to approximately 16% of phenotypic variation (approximately 20% of heritable variation). Although additional approaches are needed to dissect the genetic architecture of polygenic human traits fully, our findings indicate that GWA studies can identify large numbers of loci that implicate biologically relevant genes and pathways.

Analyses of the yeast Rad51 recombinase A265V mutant reveal different in vivo roles of Swi2-like factors

The Saccharomyces cerevisiae Swi2-like factors Rad54 and Rdh54 play multifaceted roles in homologous recombination via their DNA translocase activity. Aside from promoting Rad51-mediated DNA strand invasion of a partner chromatid, Rad54 and Rdh54 can remove Rad51 from duplex DNA for intracellular recycling. Although the in vitro properties of the two proteins are similar, differences between the phenotypes of the null allele mutants suggest that they play different roles in vivo. Through the isolation of a novel RAD51 allele encoding a protein with reduced affinity for DNA, we provide evidence that Rad54 and Rdh54 have different in vivo interactions with Rad51. The mutant Rad51 forms a complex on duplex DNA that is more susceptible to dissociation by Rdh54. This Rad51 variant distinguishes the in vivo functions of Rad54 and Rdh54, leading to the conclusion that two translocases remove Rad51 from different substrates in vivo. Additionally, we show that a third Swi2-like factor, Uls1, contributes toward Rad51 clearance from chromatin in the absence of Rad54 and Rdh54, and define a hierarchy of action of the Swi2-like translocases for chromosome damage repair

An exploratory phenome wide association study linking asthma and liver disease genetic variants to electronic health records from the Estonian Biobank

<div><p>The Estonian Biobank, governed by the Institute of Genomics at the University of Tartu (Biobank), has stored genetic material/DNA and continuously collected data since 2002 on a total of 52,274 individuals representing ~5% of the Estonian adult population and is increasing. To explore the utility of data available in the Biobank, we conducted a phenome-wide association study (PheWAS) in two areas of interest to healthcare researchers; asthma and liver disease. We used 11 asthma and 13 liver disease-associated single nucleotide polymorphisms (SNPs), identified from published genome-wide association studies, to test our ability to detect established associations. We confirmed 2 asthma and 5 liver disease associated variants at nominal significance and directionally consistent with published results. We found 2 associations that were opposite to what was published before (rs4374383:AA increases risk of NASH/NAFLD, rs11597086 increases ALT level). Three SNP-diagnosis pairs passed the phenome-wide significance threshold: rs9273349 and E06 (thyroiditis, p = 5.50x10^-8); rs9273349 and E10 (type-1 diabetes, p = 2.60x10^-7); and rs2281135 and K76 (non-alcoholic liver diseases, including NAFLD, p = 4.10x10^-7). We have validated our approach and confirmed the quality of the data for these conditions. Importantly, we demonstrate that the extensive amount of genetic and medical information from the Estonian Biobank can be successfully utilized for scientific research.</p></div

Individual reactions to stress predict performance during a critical aviation incident

© 2014, © 2014 Taylor & Francis. Background: Understanding the influence of stress on human performance is of theoretical and practical importance. An individual's reaction to stress predicts their subsequent performance; with a “challenge” response to stress leading to better performance than a “threat” response. However, this contention has not been tested in truly stressful environments with highly skilled individuals. Furthermore, the effect of challenge and threat responses on attentional control during visuomotor tasks is poorly understood. Design: Thus, this study aimed to examine individual reactions to stress and their influence on attentional control, among a cohort of commercial pilots performing a stressful flight assessment. Methods: Sixteen pilots performed an “engine failure on take-off” scenario, in a high-fidelity flight simulator. Reactions to stress were indexed via self-report; performance was assessed subjectively (flight instructor assessment) and objectively (simulator metrics); gaze behavior data were captured using a mobile eye tracker, and measures of attentional control were subsequently calculated (search rate, stimulus driven attention, and entropy). Results: Hierarchical regression analyses revealed that a threat response was associated with poorer performance and disrupted attentional control. Conclusion: The findings add to previous research showing that individual reactions to stress influence performance and shed light on the processes through which stress influences performance

Genome-wide association study identifies six new loci influencing pulse pressure and mean arterial pressure.

Numerous genetic loci have been associated with systolic blood pressure (SBP) and diastolic blood pressure (DBP) in Europeans. We now report genome-wide association studies of pulse pressure (PP) and mean arterial pressure (MAP). In discovery (N = 74,064) and follow-up studies (N = 48,607), we identified at genome-wide significance (P = 2.7 × 10(-8) to P = 2.3 × 10(-13)) four new PP loci (at 4q12 near CHIC2, 7q22.3 near PIK3CG, 8q24.12 in NOV and 11q24.3 near ADAMTS8), two new MAP loci (3p21.31 in MAP4 and 10q25.3 near ADRB1) and one locus associated with both of these traits (2q24.3 near FIGN) that has also recently been associated with SBP in east Asians. For three of the new PP loci, the estimated effect for SBP was opposite of that for DBP, in contrast to the majority of common SBP- and DBP-associated variants, which show concordant effects on both traits. These findings suggest new genetic pathways underlying blood pressure variation, some of which may differentially influence SBP and DBP