Construction of a Cell Line for Proportion Controlled Alternative Gene Activation

Department of Biological SciencesUnderstanding regulatory networks and gene regulation, in particular, are amongst the several fundamental goals in cell biology and genetics, and traditional ideas on these concerns form a substantial part of our knowledge concerning cells, organs, and organisms. Traditionally, these quandaries are reviewed through experiments conducted on cell populations, and the roles of distinct genes are tested by suppressing or inducing their expression in a wide number of cells by various means. Biological responses are in common estimated over a large number of cells, while the proportion of induced cells is seldom deemed as a pivotal parameter. One then infers a knowledge that is held to be the idea of how an individual cell works intrinsically. Our current belief of most intracellular regulation pathways relies on this empiric scheme and interpretation framework, whereby the average response is considered to be an intrinsic property of the average cell and, therefore of each cell if the cell population is homogeneous. It is a well-established concept that the collective behavior of a set of interacting objects, be it molecules in a liquid or human individuals in a population, is potentially different from the behavior of isolated objects of the same kind. Collective properties are not necessarily the mere cumulative or average contribution of the intrinsic properties of isolated objects. Reciprocally, the understanding of the collective action cannot be used to foretell the behavior of individual objects, unless interactions are disregarded. As a consequence, our knowledge established by assessing the response of a population of interacting cells cannot be considered to reflect the intrinsic features of individual cells, and the way individual cells respond to some extent depend on the state of the surrounding cells and of the population. It also inflates the enigma of the notion of intrinsic properties for cells, like epithelial cells, that depends on their neighbors for the definition of their very phenotype. To resort this, in this present project, we propose to explore the collective behavior of cells and distinguish their intrinsic properties from non-intrinsic ones. The abstract model underlying the proposed experiments consists of a homogeneous population of cells, in which a test-gene is activated either in all cells or a controlled proportion of randomly distributed cells or cell cluster. If the response exhibited by activated cells is found to be invariant for any heterogeneous gene activation pattern, it will be established as intrinsic. Conversely, if cell-cell interactions matter for shaping the response of cells subjected to the activation of the test-gene, one expects that response to differ from the different heterogeneous activation patterns, e.g., with varying outcomes when the activation is distributed to a minority versus a majority of cells. In this abstract model, cells are supposedly identical, with no heterogeneity other than receiving the activation or not. The expected pattern dependence effect does not the result from a pre-existing heterogeneity of cells, but that of the activation pattern. The expected outcome, for the test-gene, is to find if a class of heterogeneous activation patterns can trigger a response that differs from the homogeneous activation pattern, and to resolve which part of the response events are subjected to a non-intrinsic control.clos