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© The Rockefeller University Press, 0021-9525/2003/3/981-a $5.00
The Journal of Cell Biology, Volume 160, Number 7, 981-a-981

DNA-free division

DNA (blue) is not essential (right) for normal spindle assembly and division (top to bottom) in fly germ cells.

On page 993, Bucciarelli et al. report the first evidence that chromosomes are not always necessary for proper spindle assembly and cell division.

The authors stumbled upon chromosome-independent cell division during a screen for meiosis mutants in Drosophila. Two of the mutants they identified, fusolo and solofuso, had chromosome segregation defects that led to secondary spermatocytes lacking chromosomes. Nonetheless, these male germ cells constructed normal centrosome-nucleated astral arrays and a typical central spindle, appropriately containing the cell cleavage protein Aurora B. A contractile ring including the usual components of the cytokinetic apparatus (such as F-actin and myosin II) formed around the midzone in the mutants, and cytokinesis progressed as in wild-type cells.

Unlike in fly spermatocytes, in all other systems studied so far, including fly and frog embryonic cells and mouse female gametes, spindle formation and progression to telophase is blocked in the absence of chromosomes. The authors of the current study can only speculate about what gives fly meiosis this unique twist. Perhaps a chromosome-independent division apparatus was a response to the particularly high ratio of microtubules to DNA in fly male meiotic spindles. Or possibly, as more cell types are examined, chromosome-free cytokinesis will be found in other systems. Either way, the findings indicate that the high concentrations of RanGTP found at chromosomes are not always necessary for spindle formation and progression to telophase, and that the interaction of microtubules emanating from two opposing asters might sometimes be enough.

Nicole LeBrasseur

lebrasn{at}rockefeller.edu

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Spindle assembly and cytokinesis in the absence of chromosomes during Drosophila male meiosis

Elisabetta Bucciarelli, Maria Grazia Giansanti, Silvia Bonaccorsi, and Maurizio Gatti
J. Cell Biol. 2003 160: 993-999. [Abstract] [Full Text] [PDF]

This Article Full Text (PDF, 763K) PPT slides of all figures Alert me when this article is cited Services Email this article Similar articles in this journal Alert me to new content in the JCB Download to citation manager Citing Articles Citing Articles via CrossRef Citing Articles via Google Scholar Google Scholar Articles by LeBrasseur, N. Search for Related Content PubMed Articles by LeBrasseur, N. Related Collections Related Article Social Bookmarking                            What's this?