Editing Invagination (section)

=== Changes in cell height ===
Invagination also often involves, and can be driven by, changes in cell height. When apical constriction occurs, this can lead to elongation of cells to maintain constant cell volume, and consequently a thickening of the epithelium. However, shortening of cells along the apical-basal axis can also help deepen the pit formed during invagination.<ref>Kondo, Takefumi, and Shigeo Hayashi. 2015. “Mechanisms of Cell Height Changes That Mediate Epithelial Invagination.” ''DGD'' 57 (4): 313–23. <nowiki>https://doi.org/10.1111/dgd.12224</nowiki>.</ref> Active changes in cell shape to cause cell shortening have been shown to contribute to invagination in a few cases. For example, in the ''Drosophila'' leg epithelium, [[Apoptosis|apoptotic]] cells shrink and pull on the apical surface of the epithelium via an apical-basal cable made up of actin and myosin.<ref>Monier, Bruno, Melanie Gettings, Guillaume Gay, Thomas Mangeat, Sonia Schott, Ana Guarner, and Magali Suzanne. 2015. “Apico-Basal Forces Exerted by Apoptotic Cells Drive Epithelium Folding.” ''Nature'' 518 (7538): 245–48. <nowiki>https://doi.org/10.1038/nature14152</nowiki>.</ref> In the invagination that occurs in [[Ascidiacea|ascidian]] gastrulation, cells first undergo apical constriction and then change their shape to become rounder ––and thus shorter along the apical-basal axis––which is responsible for the completion of the invagination movement.<ref>Sherrard, Kristin, François Robin, Patrick Lemaire, and Edwin Munro. 2010. “Sequential Activation of Apical and Basolateral Contractility Drives Ascidian Endoderm Invagination.” ''Current Biology'' 20 (17): 1499–1510. <nowiki>https://doi.org/10.1016/j.cub.2010.06.075</nowiki>.</ref> During [[cell division]], cells also naturally take on a rounded morphology. The rapid drop in cell height caused by rounding of cells during mitosis has also been implicated in invagination of the ''Drosophila'' [[Trachea|tracheal]] placode.<ref>Kondo, Takefumi, and Shigeo Hayashi. 2013. “Mitotic Cell Rounding Accelerates Epithelial Invagination.” ''Nature'' 494 (7435): 125–29. <nowiki>https://doi.org/10.1038/nature11792</nowiki>.</ref>