Grant: Discovery Grants Program - Individual

From microbial cultures to individual cells in multicellular organisms, all cell populations exhibit phenotypic diversity. Even genetically identical individuals exposed to the same environment can display differences - these differences are referred to as phenotypic heterogeneity. A number of mechanisms can give rise to heterogeneity, but a global view of how combinations of factors shape the phenotypic landscape is missing. The long-term objective of this research program is to understand how phenotypic differences among genetically identical individuals arise from interactions between environmental, stochastic, and physiological sources of variation, and how these differences affect cellular responses and decision making. Due to the broad implications of this phenomenon, there has been a growing interest in phenotypic heterogeneity from diverse fields in NSE, including evolutionary and developmental biology. However, few research programs focus on distributions of phenotypes present among individual cells, while studies of population averages abound. A comprehensive understanding of complex interactions between different factors that lead to phenotypic heterogeneity demands the use of systematic approaches with single-cell resolution in genetically tractable systems and controlled experimental environments. High-content imaging, which combines high-throughput microscopy with multi-parametric image and data analyses, provides rich information about the spatiotemporal properties of biological systems and mechanistic insights on phenotype development at the single cell level, and is thus ideally suited to study phenotypic heterogeneity. In this proposal we will use budding yeast, which is the premier model system for exploring complex genetics of eukaryotic organisms, to determine the effect and mutual relationship of a defined set of non-genetic sources of phenotypic heterogeneity in genetically identical cells grown in a constant environment. To this end, our short-term objectives are to: i) Establish a robust high-content imaging pipeline to study combinations of non-genetic sources of phenotypic heterogeneity; ii) Quantify phenotypic variability and the contribution of selected non-genetic sources to phenotypic heterogeneity in populations of genetically identical cells; iii) Generate the first large-scale genotype-environment-physiology interaction map. Collectively, discoveries made by this proposal will lead to advancements in our understanding of the mechanisms of phenotypic heterogeneity, and of the interplay between genotype, the environment and cell physiology in shaping a cell's behaviour. This knowledge is required to better understand and predict cellular adaptation, population dynamics and evolution, and the plasticity and complexity of the phenotypic landscape. Ultimately, these findings will profoundly impact our understanding of the relationship between genotype and phenotype.