Gene expression in mammalian cells is tightly controlled and depends on the interplay between the production, degradation and localization of RNA and proteins. Each of these processes is highly regulated, but it remains largely unclear which of these is the dominant process determining the final concentration of each protein in each cell state or time point on a genomic scale.In my outgoing phase, I will systematically study the dynamics of gene expression control of mammalian cells, using the clinically-relevant model system of immune dendritic cells (DCs) responding to the pathogen component LPS. First, I will evaluate the contribution of protein production and degradation to changes in overall protein levels following LPS stimulation. Second, I will integrate the generated data with already available data about the dynamics of the RNA life cycle to build an unprecedented quantitative genome-scale model of the temporal dynamics of gene expression, from transcription to protein degradation. Third, I will study systematically the translational potential of short non-canonical ORFs encoded on putative long non-coding RNAs. Finally, I will use these data to select new candidate regulators of the immune response of DCs and validate and refine their roles by systematic genetic perturbations followed by signature-scale monitoring.In my returning phase, I will apply the experience gained and methods developed during my outgoing phase to systematically study gene expression in hippocampal neurons upon synaptic stimulation. In particular, I will study gene expression control in somata and dendrites separately, thus considering spatial and temporal regulation of gene expression dynamics.The proposed study will provide insight into the temporal and spatial expression dynamics of both canonical and short-canonical ORFs in two independent mammalian model systems. This will also lead to the identification of key regulators of the immune response and of memory formation.