Developmental Biology

Beams and Hangers

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Science  19 Aug 2005:
Vol. 309, Issue 5738, pp. 1157
DOI: 10.1126/science.309.5738.1157a

The fully grown oocyte of the frog Xenopus laevis contains considerable internal architecture—in particular, an extensive cytokeratin network—even though it is only a single cell. One of the features of this network is that it compartmentalizes maternally encoded RNA molecules, which are important for development of the embryo after fertilization; disruption of the network results in release of these RNAs.

Kloc et al. show that the cytokeratin network is also necessary for formation of the germinal granules during oogenesis. A class of maternal RNA molecules forms part of the germinal granules, which accumulate in the oocyte and are passed into a small but important lineage of cells: the primordial germ cells that will eventually give rise to eggs and sperm. The cytokeratin network depends for its own structural integrity on two molecules, VegT and Xlsirts, and both of these function in this setting as RNAs, not as translated proteins. The structural components of this cellular network thus seem to include RNA molecules as well as cytokeratin filaments. — PJH

Development 132, 3445 (2005).

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