Cohesin Smc1beta determines meiotic chromatin axis loop organization.
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 1beta (Smc1beta), a mammalian chromosome-associated meiosis-specific cohesin. Our results suggest that in addition to its role in sister chromatid cohesion, Smc1beta determines meiotic chromatin loop organization.
Novak
Ivana
I
Department of Cell and Molecular Biology, Karolinska Institutet, SE-171 77 Stockholm, Sweden.
Wang
Hong
H
Revenkova
Ekaterina
E
Jessberger
Rolf
R
Scherthan
Harry
H
Höög
Christer
C
D000818:Animals; D018797:Cell Cycle Proteins / Q000502:physiology*; D002843:Chromatin / Q000235:genetics / Q000648:ultrastructure*; D020090:Chromosome Segregation / Q000235:genetics / Q000502:physiology; D004268:DNA-Binding Proteins; D008540:Meiosis / Q000235:genetics* / Q000502:physiology; D051379:Mice; D009687:Nuclear Proteins / Q000235:genetics / Q000502:physiology; D009865:Oocytes / Q000166:cytology / Q000648:ultrastructure
D018797:Cell Cycle Proteins; D002843:Chromatin; D004268:DNA-Binding Proteins; D009687:Nuclear Proteins; C438001:Smc1l2 protein, mouse; C490062:Sycp3 protein, mouse