Published online January 7, 2008
doi:10.1083/jcb.200706136
The Journal of Cell Biology, Vol. 180, No. 1, 83-90
The Rockefeller University Press, 0021-9525 $30.00
© 2008 Novak et al.
Cohesin Smc1β determines meiotic chromatin axis loop organization
Ivana Novak1,
Hong Wang1,
Ekaterina Revenkova2,
Rolf Jessberger2,3,
Harry Scherthan4, and
Christer Höög1
1 Department of Cell and Molecular Biology, Karolinska Institutet, SE-171 77 Stockholm, Sweden
2 Department of Gene and Cell Medicine, Mount Sinai School of Medicine, New York, NY 10029
3 Institute of Physiological Chemistry, Dresden University of Technology, D-01307 Dresden, Germany
4 Max Planck Institute for Molecular Genetics, D-14195 Berlin, Germany
Correspondence to Christer Höög: christer.hoog{at}ki.se
Meiotic chromosomes consist of proteinaceous axial structures from which chromatin loops emerge. Although we know that loop density along the meiotic chromosome axis is conserved in organisms with different genome sizes, the basis for the regular spacing of chromatin loops and their organization is largely unknown. We use two mouse model systems in which the postreplicative meiotic chromosome axes in the mutant oocytes are either longer or shorter than in wild-type oocytes. We observe a strict correlation between chromosome axis extension and a general and reciprocal shortening of chromatin loop size. However, in oocytes with a shorter chromosome axis, only a subset of the chromatin loops is extended. We find that the changes in chromatin loop size observed in oocytes with shorter or longer chromosome axes depend on the structural maintenance of chromosomes 1β (Smc1β), a mammalian chromosome–associated meiosis-specific cohesin. Our results suggest that in addition to its role in sister chromatid cohesion, Smc1β determines meiotic chromatin loop organization.
H. Scherthan's present address is Institut für Radiobiologie der Bundeswehr, D-80937 Munich, Germany.
Abbreviations used in this paper: DKO, double knockout; SC, synaptonemal complex; SKO, single knockout; wt, wild type.

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