Notch signalling influences cell fate decisions and HOX gene induction in axial progenitors

The generation of the post-cranial embryonic body relies on the coordinated production of spinal cord neurectoderm and presomitic mesoderm cells from neuromesodermal progenitors (NMPs). This process is orchestrated by pro-neural and pro-mesodermal transcription factors that are co-expressed in NMPs together with Hox genes, which are critical for axial allocation of NMP derivatives. NMPs reside in a posterior growth region, which is marked by the expression of Wnt, FGF and Notch signalling components. While the importance of Wnt and FGF in influencing the induction and differentiation of NMPs is well established, the precise role of Notch remains unclear. Here, we show that the Wnt/FGF-driven induction of NMPs from human embryonic stem cells (hESCs) relies on Notch signalling. Using hESC-derived NMPs and chick embryo grafting, we demonstrate that Notch directs a pro-mesodermal character at the expense of neural fate. We show that Notch also contributes to activation of HOX gene expression in human NMPs, partly in a non-cell-autonomous manner. Finally, we provide evidence that Notch exerts its effects via the establishment of a negative feedback loop with FGF signalling.</p

Cohesin Proteins Promote Ribosomal RNA Production and Protein Translation in Yeast and Human Cells

Cohesin is a protein complex known for its essential role in chromosome segregation. However, cohesin and associated factors have additional functions in transcription, DNA damage repair, and chromosome condensation. The human cohesinopathy diseases are thought to stem not from defects in chromosome segregation but from gene expression. The role of cohesin in gene expression is not well understood. We used budding yeast strains bearing mutations analogous to the human cohesinopathy disease alleles under control of their native promoter to study gene expression. These mutations do not significantly affect chromosome segregation. Transcriptional profiling reveals that many targets of the transcriptional activator Gcn4 are induced in the eco1-W216G mutant background. The upregulation of Gcn4 was observed in many cohesin mutants, and this observation suggested protein translation was reduced. We demonstrate that the cohesinopathy mutations eco1-W216G and smc1-Q843Δ are associated with defects in ribosome biogenesis and a reduction in the actively translating fraction of ribosomes, eiF2α-phosphorylation, and 35S-methionine incorporation, all of which indicate a deficit in protein translation. Metabolic labeling shows that the eco1-W216G and smc1-Q843Δ mutants produce less ribosomal RNA, which is expected to constrain ribosome biogenesis. Further analysis shows that the production of rRNA from an individual repeat is reduced while copy number remains unchanged. Similar defects in rRNA production and protein translation are observed in a human Roberts syndrome cell line. In addition, cohesion is defective specifically at the rDNA locus in the eco1-W216G mutant, as has been previously reported for Roberts syndrome. Collectively, our data suggest that cohesin proteins normally facilitate production of ribosomal RNA and protein translation, and this is one way they can influence gene expression. Reduced translational capacity could contribute to the human cohesinopathies

Numerical simulations of mesoscale convective systems: techniques for comparison with observations and a high resolution analysis of flow patterns in the convective region and transition zone of a simulated mcs

Comparison between numerical simulations and observations is useful for improving understanding of weather phenomena, such as mesoscale convective systems (MCSs). The Bow Echo and Mesoscale Convective Experiment (BAMEX) provides a multi-sensor, high-resolution dataset that can be used for such comparisons. In Chapter 2 of this work, airborne radar observations taken during the 9-10 June 2003 MCS observed during BAMEX are compared against numerical simulations performed using the Weather Research and Forecasting (WRF) model. Comparisons are carried out using the equivalent radar reflectivity factor and 3-D wind fields derived from quad-Doppler radial velocity measurements from two research aircraft using the well-documented contoured frequency by altitude (CFAD) technique to compare vertical variability between the model and the observations. In addition, in order to quantify horizontal variability, a contoured frequency by distance diagram (CFDD) and average altitude per bin diagram (AABD) are introduced, which display frequency and altitude (respectively) of a variable at a given horizontal distance from a fixed location in the domain. Using these statistical techniques, a quantitative comparison of the observed and simulated rear inflow jet (RIJ) and other kinematic features of the MCS is carried out at varying times in the MCS evolution to assess the level of agreement of the storm kinematics and morphology. The new statistical analysis techniques show that the RIJ remains elevated in both the simulation and the observations, as well as structural differences in the pre-storm environment between the simulation and observations. Chapter 3 investigates the mechanism(s) by which downdrafts at the rear of the convective precipitation and in the transition zone affect the maintenance and evolution of a simulated “early nocturnal” (approximately one hour after sunset) MCS. Additionally, the impact of melting in the transition zone on the MCS will be examined as well as the fine scale structure of the convective region and transition zone. While the storm was not elevated during the time period of this study, transition zone downdrafts were found to still affect the convective updrafts in addition to their immediate environment, including the horizontal velocity and temperature fields. The convective updraft was found to be highly unsteady, frequently changing between one or two coherent primary updrafts and a series of smaller adjacent updraft cores. Subsidence enhanced by entrainment occurred around these cores, producing downdrafts near the leading edge of the convective precipitation. In areas where precipitation was occurring, the melting layer divided a downdraft-dominated regime below it from an updraft-dominated regime above it. The downdrafts, initially induced by melting, were enhanced by evaporative cooling caused by precipitation falling into the dry rear inflow jet beneath the melting layer. Thus, melting of precipitation reinforced the cold pool and helped to maintain the MCS. Trajectory analysis showed that air parcels within the core of the rear inflow jet, which contained low θe air, could be ingested into the convective updraft cores, possibly reducing the buoyancy of the air within the updraft

Numerical simulations of mesoscale convective systems: techniques for comparison with observations and a high resolution analysis of flow patterns in the convective region and transition zone of a simulated mcs

Comparison between numerical simulations and observations is useful for improving understanding of weather phenomena, such as mesoscale convective systems (MCSs). The Bow Echo and Mesoscale Convective Experiment (BAMEX) provides a multi-sensor, high-resolution dataset that can be used for such comparisons. In Chapter 2 of this work, airborne radar observations taken during the 9-10 June 2003 MCS observed during BAMEX are compared against numerical simulations performed using the Weather Research and Forecasting (WRF) model. Comparisons are carried out using the equivalent radar reflectivity factor and 3-D wind fields derived from quad-Doppler radial velocity measurements from two research aircraft using the well-documented contoured frequency by altitude (CFAD) technique to compare vertical variability between the model and the observations. In addition, in order to quantify horizontal variability, a contoured frequency by distance diagram (CFDD) and average altitude per bin diagram (AABD) are introduced, which display frequency and altitude (respectively) of a variable at a given horizontal distance from a fixed location in the domain. Using these statistical techniques, a quantitative comparison of the observed and simulated rear inflow jet (RIJ) and other kinematic features of the MCS is carried out at varying times in the MCS evolution to assess the level of agreement of the storm kinematics and morphology. The new statistical analysis techniques show that the RIJ remains elevated in both the simulation and the observations, as well as structural differences in the pre-storm environment between the simulation and observations. Chapter 3 investigates the mechanism(s) by which downdrafts at the rear of the convective precipitation and in the transition zone affect the maintenance and evolution of a simulated “early nocturnal” (approximately one hour after sunset) MCS. Additionally, the impact of melting in the transition zone on the MCS will be examined as well as the fine scale structure of the convective region and transition zone. While the storm was not elevated during the time period of this study, transition zone downdrafts were found to still affect the convective updrafts in addition to their immediate environment, including the horizontal velocity and temperature fields. The convective updraft was found to be highly unsteady, frequently changing between one or two coherent primary updrafts and a series of smaller adjacent updraft cores. Subsidence enhanced by entrainment occurred around these cores, producing downdrafts near the leading edge of the convective precipitation. In areas where precipitation was occurring, the melting layer divided a downdraft-dominated regime below it from an updraft-dominated regime above it. The downdrafts, initially induced by melting, were enhanced by evaporative cooling caused by precipitation falling into the dry rear inflow jet beneath the melting layer. Thus, melting of precipitation reinforced the cold pool and helped to maintain the MCS. Trajectory analysis showed that air parcels within the core of the rear inflow jet, which contained low θe air, could be ingested into the convective updraft cores, possibly reducing the buoyancy of the air within the updraft

Coding Brands on Twitter : How Are Message Choice and Interactivity Associated With Consumers' Brand Loyalty?

Color poster with text, graphs, charts, and tables.Our research aims to identify how brands use Twitter to strengthen brand loyalty through the use of interactivity and strategic messages. We analyzed what types of language and communication stimulate brand loyalty on Twitter.University of Wisconsin--Eau Claire Office of Research and Sponsored Program

The coordinate regulation of pharyngeal development in C. elegans by lin-35/Rb, pha-1, and ubc-18

Organ development is a complex process involving the coordination of cell proliferation, differentiation, and morphogenetic events. Using a screen to identify genes that function coordinately with lin-35/Rb during animal development, we have isolated a weak loss-of-function (LOF) mutation in pha-1. lin-35; pha-1 double mutants are defective at an early step in pharyngeal morphogenesis leading to an abnormal pharyngeal architecture. pha-1 is also synthetically lethal with other class B synthetic multivulval (SynMuv) genes including the C. elegans E2F homolog, efl-1. Reporter analyses indicate that pha-1 is broadly expressed during embryonic development and that its functions reside in the cytoplasm. We also provide genetic and phenotypic evidence to support the model that PHA-1, a novel protein, and UBC-18, a ubiquitin-conjugating enzyme that we have previously shown to function with lin-35 during pharyngeal development, act in parallel pathways to regulate the activity of a common cellular target

The coordinate regulation of pharyngeal development in C. elegans by lin-35/Rb, pha-1, and ubc-18

Abstract Organ development is a complex process involving the coordination of cell proliferation, differentiation, and morphogenetic events. Using a screen to identify genes that function coordinately with lin-35/Rb during animal development, we have isolated a weak loss-of-function (LOF) mutation in pha-1. lin-35; pha-1 double mutants are defective at an early step in pharyngeal morphogenesis leading to an abnormal pharyngeal architecture. pha-1 is also synthetically lethal with other class B synthetic multivulval (SynMuv) genes including the C. elegans E2F homolog, efl-1. Reporter analyses indicate that pha-1 is broadly expressed during embryonic development and that its functions reside in the cytoplasm. We also provide genetic and phenotypic evidence to support the model that PHA-1, a novel protein, and UBC-18, a ubiquitinconjugating enzyme that we have previously shown to function with lin-35 during pharyngeal development, act in parallel pathways to regulate the activity of a common cellular target