How many cell polarity related genes are conserved from Tetrahymena to metazoa?

Abstract

Cell polarity can be seen as an asymmetric distribution and spatial arrangement of biomolecules, cellular components (e.g., membrane domains and organelles such as the Golgi apparatus, mitochondria, cilia, and others) and cytoskeleton such that, their specific positioning in the cell, in close relationship with their functions, generates a structural/functional asymmetry that can be conserved and transmitted to new cells during cell division. In fact, cell polarity controls the morphology from single cells to whole tissues. Cellular organizational/functional asymmetry is required for a variety of cell functions in both unicellular and multicellular organisms such as correct symmetric and asymmetric cell division, differentiation, motility and cell migration. Moreover, in mammalian cells, polarity can be challenged by environmental cues, and cells are able to remodel their intrinsic polarity. The ciliate Tetrahymena thermophila is a highly differentiated cell organism that possesses a permanent anterior-posterior axis and left-right asymmetry. Tetrahymena cells are also characterized by a complex cortex where basal bodies are longitudinally arranged in close association with cytoskeleton appendages and networks originating a complex pattern. The molecular mechanisms that control the formation and regeneration of this complex cortical patterning in each daughter cell after cytokinesis are still not well understood. We have shown that the Tetrahymena Mob1 protein is essential for maintenance and regeneration of cell polarity, proper cell proportions, correct division plane placement, and finally to cytokinesis completion. At the time, Mob1 was already described as a member of the mitotic exit network, a signaling cascade that controls mitosis to interphase transition. In metazoans, Mob1 is a member of the Hippo signaling pathway, a major conserved mechanism governing cell contact inhibition and organ size control. Due to its cell features Tetrahymena emerges as a good model to address the regulatory mechanisms underlying cell polarity/morphogenesis/and cell division. To test this idea we went throughout the Tetrahymena genome looking for genes already described to be involved in cell polarity in other unicellular and multicellular model organisms. Interestingly, some of these core genes involved in cell polarity appear to be conserved in this ciliate. In this presentation we will discuss our findings.