We study signaling cascades central to growth and development, using molecular, genetic, cellular, and biochemical techniques, and the model eukaryote Dictyostelium to define cell autonomous and non-autonomous signal transduction pathways that regulate development. Dictyostelium grow as individual cells in enriched media, but develop multicellularly upon nutrient depletion. We have probed a variety of signaling pathways to better understand mechanisms and circuits for focus on human diseases. In certain instances, we extend studies to mammalian models. CHARGE syndrome is an extremely severe, multi-system congenital disorder caused by loss-of-functions mutations in the human CHD type III variant CHD7. We used genome-wide analysis of nucleosome positioning and transcription profiling to investigate the in vivo relationship between nucleosome positioning and gene expression during development of wild type (WT) Dictyostelium and mutant cells lacking ChdC, a CHD7 protein ortholog. We demonstrate major nucleosome positional changes associated with developmental gene regulation in WT. Loss of chdC caused an increase of intragenic nucleosome spacing and mis-regulation of gene expression, affecting 50% of the genes that are repositioned during WT development. These analyses demonstrate active nucleosome repositioning during Dictyostelium multicellular development, establish an in vivo function of CHD Type III chromatin remodeling proteins in this process, and reveal the detailed relationship between nucleosome positioning and gene regulation, as cells transition between developmental states. Aspects of innate immunity derive from characteristics inherent to phagocytes, including chemotaxis toward and engulfment of unicellular organisms or cell debris. Ligand chemotaxis has been biochemically investigated using mammalian and model systems, but precision of chemotaxis towards ligands being actively secreted by live bacteria is not well studied, nor has there been systematic analyses of interrelationships between chemotaxis and phagocytosis. The genetic/molecular model Dictyostelium and mammalian phagocytes share mechanistic pathways for chemotaxis and phagocytosis; Dictyostelium chemotax toward bacteria and phagocytose them as food sources. We quantified Dictyostelium chemotaxis towards live bacteria and demonstrate high sensitivity to multiple bacterially-secreted chemoattractants. Additive/competitive assays indicate that intracellular signaling-networks for multiple ligands utilize independent upstream adaptive mechanisms, but common downstream targets, thus amplifying detection at low signal propagation, but strengthening discrimination of multiple inputs. Finally, analyses of signaling-networks for chemotaxis and phagocytosis indicate that chemoattractant receptor-signaling is not essential for bacterial phagocytosis. Excessive cellular lipid storage can be a risk factor for metabolic disorders, including insulin resistance, cardiovascular disease, and hepatic steatosis. Intracellular lipid droplets are unique organelles that store metabolic precursors of cellular energy, membrane biosynthesis, steroid hormone synthesis, and signaling. The perilipins are a multi-protein family that targets lipid droplet surfaces and regulates lipid storage and hydrolysis. We show that loss of Plin2 in cultured myotubes enhances lipolysis and re-directs the metabolic energy balance from glucose oxidation towards fatty acid oxidation. Myocardial triglycerides stored in lipid droplets are important in regulating the intracellular delivery of fatty acids for energy generation in mitochondria, for membrane biosynthesis, and as agonists for intracellular signaling. We showed that deficiency in the lipid droplet protein Plin5 markedly reduces triglyceride storage in cardiomyocytes and increases the flux of fatty acids into phospholipids; mitochondrial oxidative capacity and mitochondrial membrane depolarization were markedly compromised.
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