Germline P Granules Are Liquid Droplets That Localize by Controlled Dissolution/Condensation

<jats:title>P Granule Conundrum</jats:title> <jats:p> In many organisms, the presumptive germ cells can be distinguished from somatic cells by the presence of distinctive cytoplasmic granules. In <jats:italic>Caenorhabditis elegans</jats:italic> , these P granules are more or less uniformly distributed in the oocyte and one-cell stage of the fertilized egg. By the end of the first cleavage, however, the anterior cell is essentially free of P granules, whereas the posterior cell still displays a prominent population of granules. Exactly how this process occurs and whether it involves directed migration of the granules is unclear. Now <jats:bold> Brangwynne <jats:italic>et al.</jats:italic> </jats:bold> (p. <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" page="1729" related-article-type="in-this-issue" vol="324" xlink:href="10.1126/science.1172046">1729</jats:related-article> , published online 21 May; see the Perspective by <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" page="1654" related-article-type="in-this-issue" vol="324" xlink:href="10.1126/science.1176523"> <jats:bold>Le Goff and Lecuit</jats:bold> </jats:related-article> ) provide evidence that localization occurs by a quite different mechanism, controlled dissolution and condensation of granule components. This type of cytoplasmic remodeling by physicochemical mechanisms can now be looked for in other cellular and developmental systems. </jats:p>