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These findings indicate that the direction in which the invagination forms is under the control of the same signaling pathway that controls planar cell polarity.

These mutants included those with defects in a developmental phenomenon known as “planar cell polarity” (often shortened to PCP), which instructs how animal cells in specific tissues become oriented in the same direction. show that mutant sea squirts that fail to orient their spindles correctly tended to form the membrane invaginations in the wrong direction as well.

Second, cutting this tip with a laser caused the invagination to quickly retract, demonstrating that it was under mechanical tension. First, the centrosome is closely connected to the tip of the invagination via microtubules.

This conclusion is based upon three lines of evidence. suggest that the invagination holds the centrosome in place to ensure that the mitotic spindle is oriented correctly. As such, the centrosome has an integral role in the assembly of the mitotic spindle: the macromolecular machine (composed of microtubules) that segregates the chromosomes during cell division. This organelle serves as an organizing center for protein filaments called microtubules. – who are based at National Institutes of Natural Sciences in Japan and Sorbonne University in France – found that the membrane invagination always projects toward an organelle in the cell known as the centrosome. This structure involves a thin finger-like protrusion from one cell’s membrane inserting itself into a pocket (or invagination) formed in the membrane of the cell in front ( Figure 1). Now, in eLife, Takefumi Negishi, Hitoyoshi Yasuo, Naoto Ueno and colleagues report the discovery of a new membrane structure that forms in the embryos of a marine creature commonly called a sea squirt ( Negishi et al., 2016). Sperm cells and nerve cells, for example, have quite complex shapes, and the cell surface can play host to a range of organelles and structures, including primary cilia and a variety of other protrusions from the cell membrane ( Singla and Reiter, 2006 Kornberg and Roy, 2014 Gerdes and Carvalho, 2008 Buszczak et al., 2016). Cells in textbooks tend to have simple shapes, with surfaces that merely separate the contents of the cell from the outside world.