Molecular Biology

Gathering in the Clouds

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Science  10 Mar 2006:
Vol. 311, Issue 5766, pp. 1347
DOI: 10.1126/science.311.5766.1347b

The chromatoid body, an electron-dense structure in the cytoplasm of mammalian male germ cells, was first described more than a century ago (see review by Parvinen); it may correspond to Drosophila nuage, which is a cloud-like fibrous material seen in germ cells. During spermatogenesis, the chromatoid body moves around, associating with the Golgi complex, mitochondria, and nuclear pores. The absence of DNA and the presence of RNA and the RNA helicase MVH (the mouse VASA homolog) have contributed to the belief that this structure is involved in the handling and storage of messenger RNAs (mRNAs).

Kotaja et al. demonstrate that the chromatoid body contains the same kinds of molecules that are found in the processing bodies of mammalian somatic cells and yeast. The endonuclease Dicer generates small RNAs that are then assembled with Argonaute into an RNA-induced silencing complex (RISC), which mediates the degradation and translational arrest of mRNAs. The authors show that Dicer interacts with MVH and that Dicer, Argonaute, and mRNA all localize to the chromatoid body. They suggest that, as an early step in posttranscriptional regulation of gene expression, both mRNAs and small RNAs may be captured by the chromatoid body as they transit the nuclear pores. — GJC

Int. J. Androl. 28, 189 (2005); Proc. Natl. Acad. Sci. U.S.A. 103, 2647 (2006).

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