In zebrafish eggs, most rapidly growing cell inhibits neighbors through mechanical signals | 2/15/2019 | Staff
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"The winner takes it all, the loser standing small"—that's not just true in the famous ABBA song, but also in animal development. Frequently, a group of cells starts out all being the same. But then one cell puts the brake on its neighbors, sending inhibitory signals that stop their differentiation. The "winning" cell, in the end, is different from its neighbors. So far, the only signalling mechanism known to be responsible for such a lateral inhibition was the Notch-Delta signalling pathway. Postdoc Peng Xia and Professor Carl-Philipp Heisenberg at the Institute of Science and Technology Austria (IST Austria), have now described a new mechanism for lateral inhibition in a publication in today's edition of Cell. In zebrafish ovarian follicles, granulosa cells in the envelope that surround the oocyte do not use the Notch-Delta signaling pathway for lateral inhibition, but compete mechanically—the winning cell grows more rapidly and inhibits the growth of its neighbors by mechanically compressing them, thereby becoming the sole micropyle precursor cell—a cell that later plays an important role for the fertilisation of the egg.

Granulosa cells surround the zebrafish egg. One cell among this group becomes markedly different; it is much bigger than all the others—this is the micropyle precursor cell (MPC). Postdoc Peng Xia and Carl-Philipp Heisenberg set out to understand how the MPC becomes differentiated among all the granulosa cells that could adopt this fate.

Experiments - Notch-Delta - Pathway - Inhibition - Situations

Early experiments showed that the Notch-Delta signaling pathway, which is responsible for lateral inhibition in most situations during development, is not involved in the process that specifies the MPC. However, the way in which the MPC grows and presses against its neighboring cells set the researchers on their next path: They decided to test whether this jostling for space plays a role.

With their experimental set-up, the researchers measured tension in the developing...
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