Homeoprotein Hbx4 represses adhesion molecule governing cytokinesis and development

Homeobox genes encode proteins with a highly conserved DNA-binding motif and provoke morphological diversification of body segments by differentially controlling the expression of downstream targets. Here, we have identified _hbx4_, one of many homeobox genes in _Dictyostelium discoideum_ and investigated its role during growth and development. In suspension, Hbx4-overexpressing cells, Hbx4^OE^, showed defects in cytokinesis and growth rate. During development, Hbx4^OE^ and _hbx4_-disrupting cells, _hbx4¯_ made differences in shape of mound and slug, cell-type proportioning from wild type KAx3 cells. These phenotypes were similar to those of mutant defective in _cadA_ encoding Ca^2+^-dependent cell adhesion molecule so that we investigated the relationship between _hbx4_ and _cadA_. Overexpression of Hbx4 inhibited the expression of _cadA_ and cAMP also failed to stimulate _cadA_ in Hbx4^OE^. Furthermore, gel mobility shift assay showed the promoter of _cadA_ contained Hbx4-binding site, indicating Hbx4 negatively regulates the expression of _cadA_. Proteome analysis revealed that overexpression of Hbx4 repressed the _rdiA_ and _abpB_ encoding rho guanine nucleotide dissociation inhibitor1, RhoGDI1 and actin bundling protein 34, ABP34, respectively. And the overexpression of _cadA_ in Hbx4^OE^ cells rescued the defects and increased mRNA level of _rdiA_, _abpB_ and one of Rho GTPase, _rac1b_. These results suggested that Hbx4 can modulate cytokinesis, cell sorting and cell-type proportioning by repressing _cadA_ that regulates GTPase-dependent signaling pathway

Development of the Fast Light Alloy Stamping Technology (FAST) towards automotive applications: experimental studies

In order to improve fuel efficiency and reduce carbon emissions for the automotive industry, a novel forming technology Fast light alloy stamping technology (FAST) for high and ultra-high strength aluminium alloy thin wall components (such as AA7075) was developed with experimental studies in this thesis. The process consists of: rapid heating, forming and in-die quenching, and incubation. A hot Stamping Simulator tool set to study FAST was successfully developed and manufactured to work in conjunction with the Gleeble 3800 thermo-mechanical testing machine. Based on this Hot Stamping Simulator, the effect of forming parameters on the formability of material and post-form strength have been studied for AA7075 2 mm blank. The effects of contact pressure, lubricant, and tool material on the Interfacial heat transfer coefficient (IHTC) have also been studied, and a mathematical model was developed in order to calculate the quenching time, predict post form strength and optimise the tool design to secure a high quenching rate, enabling the full post-form strength to be retained. Verification tests for the FAST process utilising AA7075 2 mm blank were conducted by forming U-shape and M-shape components. A standard testing procedure was developed for different materials and manufacturer requirements and was verified by studying 6 test cases. Finally, as a new forming process, conclusions and recommendations are made outlining additional factors to be studied to enable the FAST process to be adopted in an industrial environment.Open Acces