Characterization of the Hoxa2 binding site in dual specificity tyrosine kinase 4 (Dyrk4) and high temperature requirement factor A 3 (HtrA3) genes

Hox proteins are evolutionarily conserved transcription factors that control important developmental pathways in morphogenesis of the embryo. The Hoxa2 gene is expressed in the developing central nervous system in rhombomeres 2 to 7 and affects cellular differentiation. Few target genes of Hoxa2 protein have been identified so far and its mechanisms of regulating gene expression remain elusive. Previous work in our laboratory isolated Hoxa2 protein binding sequences from the E18 mouse spinal cord and hindbrain tissues using chromatin immunoprecipitation (ChIP). All isolated DNA fragments contain conserved GATG motifs. Sequence analysis revealed that one fragment belongs to the high temperature requirement factor A 3 (HtrA3) gene and another fragment belongs to the Dual specificity tyrosine kinase 4 (Dyrk4) gene. In this study, direct binding of Hoxa2 protein to the HtrA3 and Dyrk4 fragments was confirmed by electrophoretic mobility shift assays (EMSA). Site-directed mutagenesis and EMSA studies revealed that Hoxa2 protein binds to the multiple GATG motifs within these fragments. HtrA3 fragment also repressed luciferase gene expression in transient transfection and luciferase assays. Mutation of the DNA fragment showed that the repressive activity was affected by the GATG motifs, suggesting Hoxa2 protein regulated gene expression by binding to the GATG motif in the cis-regulatory element. In contrast to the inhibitory activity of Hoxa2 protein, a Hoxa2-VP16 fusion protein (Hoxa2 fused with an activation domain of a virion protein from herpes simplex virus) transactivates the luciferase expression by binding to GATG sites. RT-PCR and immunohistochemistry analysis revealed an upregulation of HtrA3 expression in Hoxa2-/- mice. This observation correlates with the inhibitory role of Hoxa2 protein acting upon the HtrA3 fragment in luciferase assays. Our data suggest that HtrA3 is a direct in vivo downstream target of Hoxa2 protein and support the activity regulation model in which Hox proteins selectively regulate target genes through occupation of multiple monomer binding sites

Impact Dynamics of Droplet Containing Particle Suspensions on Deep Liquid Pool

Droplet impact on surfaces is ubiquitous in many natural and industrial processes. While the impact dynamics of droplets composed of simple fluids have been studied extensively, droplets containing particles are less explored, but are more application relevant. The non-Newtonian behavior of particle suspension introduces new physics affecting the impact dynamics. Here, we investigated the impact dynamics of droplets containing cornstarch particles on a deep water pool and systematically characterized the impact outcomes with various Weber number and particle volume fractions. Distinctive phenomena compared to Newtonian droplet impact have been observed. A regime map of the impact outcomes is unveiled and the transition boundaries are quantified with scaling analysis. Rheology of the suspension is found to play a pivotal role in giving rise to distinct impact outcomes. The results lay the foundation for further characterization of the dynamics of suspension droplet impacting on liquid surfaces and can be translated to other suspension fluids

Life Cycle Energy Demand and Greenhouse Gas Emissions in Chinas road transport sector : Future trends and Policy Implications

PhDA critical evaluation of the national profile of energy supply and demand and the associated greenhouse gas (OHO) emissions in China has been conducted. The contribution of the transport sector in China, the road transport sector in particular, to China's overall energy demand and OHO emissions has been assessed and compared with values for other countries. Approaches for reducing energy demand and OHO emissions in the road transport sector worldwide have been reviewed. A detailed bottom-up model has been developed using 'LEAP' software, to estimate future energy demand and OHO emissions in China's road transport sector, incorporating China's recent efforts in alternative fuel promotion. Modelling approach and historical data used have been tested and verified to ensure reliability. Two scenarios have been designed to describe the future strategies relating to the development of China's road transport sector between 2005 and 2030. The 'Business as Usual' scenario is used as a baseline reference scenario, in which the government is assumed to do nothing to influence the long-term trends of road transport energy demand. The 'Best Case' scenario is considered to be the most optimized case where a series of available reduction measures are assumed to be implemented. Energy demand and OHO emissions in China's road transport sector up to 2030 are estimated in these two scenarios. The reduction potential and the relative contribution of each measure have been estimated. A 'life cycle assessment' model for the road transport sector has been developed. The life cycle energy demand and OHO emissions in China's road transport sector are estimated using the model. The reduction potential and the relative contribution of each measure have been re-assessed from a life cycle perspective. Potential impacts on global oil resources, availability and prices are discussed. The importance of life cycle assessment in evaluating the effects of different reduction measures is discussed. Policy implications are presente