First published online November 10, 2004
Journal of Cell Science 117, 2402e (2004)
© The Company of Biologists Limited
Meiosis without synaptonemal complexes
Tetrahymena thermophila, like Schizosaccharomyces pombe, is one of a select group of organisms that perform meiotic recombination without forming synaptonemal complexes – the structures that usually hold paired chromosomes together. T. thermophila meiosis is unusual in several respects, involving dramatic elongation of the micronucleus that contains the germline DNA to form a thread-like crescent. The arrangement of chromosomes during this process has been hotly debated. Presenting detailed immunofluorescence and FISH analyses, Josef Loidl and Harry Scherthan now greatly extend our understanding of their organization (see p. 5791). They first disprove the 50-year-old hypothesis that the chromosomes are arranged end-to-end in the crescents. Instead these form parallel bundles; their telomeres lie at one end, and loci occupy fixed positions along the crescent. The authors subsequently establish the points at which homologous chromosomes pair, double-stranded breaks form and the recombination protein Rad51 is recruited. They propose that the elongation of the micronucleus produces the polarized arrangement of the T. thermophila chromosomes at meiosis and that this promotes juxtaposition of homologous regions without the need for synaptonemal complexes.
Related articles in JCS:
- Organization and pairing of meiotic chromosomes in the ciliate Tetrahymena thermophila
- Josef Loidl and Harry Scherthan
JCS 2004 117: 5791-5801.
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