Cell biologists make amazing discoveries using cells grown flat on culture dishes, yet the cells in an organism grow and function in three dimensions. Some cell biologists use clever tricks to understand how cells function in three dimensions by using cells cultured in gels, and they find out very valuable information.
Throughout biology there are many cases of oriented cell division, during which a cell orients the mitotic spindle on a specific axis. These cell divisions can occur throughout development in stem cell divisions, tissue morphogenesis, and epithelial sheet formation. Epithelial sheets are monolayers of polarized cells, and cells must divide within the plane of the sheet in order to maintain the monolayer. A recent paper uses cultured mammalian cells grown as cysts as a model for epithelial cell divisions, and describes the important role of a protein called Pins in ensuring that cell divisions are oriented correctly. Hao and colleagues found that the correct localization of Pins on the surface of epithelial cells is regulated by the Par3 and aPKC polarity proteins. Images above are of cysts with (left) or without (right) Par3. While the wild type cyst has one lumen facing the apical surface of cells (green), cysts without Par3 form multiple lumens.Hao, Y., Du, Q., Chen, X., Zheng, Z., Balsbaugh, J., Maitra, S., Shabanowitz, J., Hunt, D., & Macara, I. (2010). Par3 Controls Epithelial Spindle Orientation by aPKC-Mediated Phosphorylation of Apical Pins Current Biology, 20 (20), 1809-1818 DOI: 10.1016/j.cub.2010.09.032
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