Who We Are
Research in Johnston Lab |
Our research focuses on mechanisms of mitotic spindle orientation. During development, animals must generate an impressive degree of cellular diversity. Moreover, the organsim must properly arrange cells in 3-dimensions such that proper tissue architecture is established and maintained. Both of these fundamental developmental processes are regulated by oriented cell divisions, which are achieved by precise positioning of the mitotic spindle during mitosis. Our lab uses a multidisciplinary approach spanning biochemistry, structural biology, cell biology, and Drosophila genetics to investigate the molecular pathways that regulate spindle orientation. Specifically, we are interested in several over-arching questions:
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Fig. 1.Spindle orientation in Drosophila S2 cells: Although genetic approaches in model organisms (e.g. Drosophila) have been instrumental in defining a 'parts list' of spindle orientation components, they have several inherent drawbacks. Most importantly, genetic alterations in the animal often have deleterious effects on other components in a given pathway, making it difficult to define the sufficiency of a given gene and to ascribe a molecular mechanism of its action. To overcome this, we have developed a novel 'induced polarity' assay in S2 cells. We use the cell-adhesion protein, Echinoid (Ed), to induce polarization of components we are interested in studying (shown in GREEN). We then examine how that component regulates the position of the mitotic spindle (shown in RED). Mutational analysis along with RNAi-mediated loss of function studies can be rapidly performed in S2 cells. In this image, a spindle orientation protein called, Pins, is attached to Ed (Ed:Pins, GREEN), and is capable of orienting the spindle during cell division.
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Our Interests |
The ability of cells to regulate the orientation of division during mitosis is a fascinating biological phenomenon. The choice between expanding the population of a given cell type and generating diversity between siblings can be decided by the orientation of the miotic spindle. This is especially important to multipotent progenitor stem cells, which must maintain a viable pool of stem cells (i.e. self-renewal), while also generating diversity of cell types during development (i.e. differentiation). Improper balance between self-renewal and differentiation can lead to several pathologies, including developmental defects as well as cancer. We are interested in understanding this biological process from a basic, fundamental framework. To that end, we aim to investigate spindle orientation pathways using a combinatorial approach of methodologies spanning in vitro and in vivo contexts. Below are representative results from our most used techniques; together they demonstrate how this combined approach can tell a complete story of newly identified spindle orientation pathways.
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