Goats from the Zagros Mountains may represent the earliest examples of goat herding.
Image credit: The Central Zagros Project.
Communicated by Lynn Margulis, University of Massachusetts, Amherst, MA, June 24, 2010 (received for review April 6, 2010)
Abstract
The nucleolinus is an RNA-rich compartment, closely apposed to or embedded within the nucleolus. Discovered over 150 y ago, fewer than two dozen articles have been published on the nucleolinus, probably because complex histochemical stains are required for its visualization in the great majority of cells. The nucleolinus has been reported in invertebrate oocytes, mammalian and amphibian epithelial cells, neurons, and several transformed cell lines. A prominent nucleolinus, clearly visible with transmitted light microscopes at 10× magnification, is present in each oocyte of the surf clam, Spisula solidissima. We observed a consistent relationship between the nucleolinus and the developing meiotic apparatus following Spisula oocyte activation. Through sonication and sucrose gradient fractionation of purified oocyte nuclei, we isolated nucleolini, extracted their RNA, and prepared an in situ riboprobe (NLi-1), which is associated specifically with the nucleolinus, confirming its unique composition. Other in situ observations revealed a NLi-1 and nucleolinar association with the developing spindle and centrosomes. Laser microsurgery that targeted the nucleolinus resulted in failed meiotic cell division in parthenogenetically activated oocytes and failed mitosis in fertilized oocytes. Although the nucleolinus may be a forgotten organelle, its demonstrated role in spindle formation suggests it deserves renewed attention.
Footnotes
- 1To whom correspondence should be addressed. E-mail: malliegro{at}mbl.edu.
Author contributions: M.A.A., J.J.H., and M.C.A. designed research; M.A.A., J.J.H., and M.C.A. performed research; M.A.A., J.J.H., and M.C.A. contributed new reagents/analytic tools; M.A.A., J.J.H., and M.C.A. analyzed data; and M.A.A., J.J.H., and M.C.A. wrote the paper.
The authors declare no conflict of interest.
Data deposition: The sequence reported in this paper has been deposited in the GenBank database (accession no. HM004235).
This article contains supporting information online at www.pnas.org/lookup/suppl/doi:10.1073/pnas.1008469107/-/DCSupplemental.
Rediscovery of the nucleolinus, a dynamic RNA-rich organelle associated with the nucleolus, spindle, and centrosomes
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