First published online 13 February 2007
doi: 10.1242/jcs.003186
Journal of Cell Science 120, 731-736 (2007)
Published by The Company of Biologists 2007
Meiotic interference among MLH1 foci requires neither an intact axial element structure nor full synapsis
Esther de Boer1,
Axel J. J. Dietrich2,
Christer Höög3,
Piet Stam4 and
Christa Heyting1,*
1 Wageningen University, Molecular Genetics group, Arboretumlaan 4, 6703 BD Wageningen, The Netherlands
2 Institute of Human Genetics, University of Amsterdam, AMC, Meibergdreef 9, 1105 AZ Amsterdam, The Netherlands
3 Department of Cell and Molecular Biology, Karolinska Institute, SE-171 77 Stockholm, Sweden
4 Wageningen University, Laboratory of Plant Breeding, Droevendaalsesteeg 1, 6708 PB Wageningen, The Netherlands

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Fig. 1. Analysis of MLH1 foci along bivalents. (A) Spread Sycp3/ oocyte labeled for SYCP1 and MLH1. (B) Merged image of the signals for MLH1, SYCP1 and meiotic cohesin REC8 on the same oocyte as in A. SYCP1 was always found on converged cohesin axes; regions of synapsis are visible as pink stretches of converged cohesin axes in this panel. (C) Merged image of the REC8 and the FISH signals on the same oocyte as in A. The FISH probes label chromosomes 1 (green), 2 (red), 18 (red) and 19 (green). The arrowhead in panels A-C indicates an MLH1 focus on two converged cohesin axes in the absence of detectable SYCP1. (D-F) Cut outs of panels A-C, showing part of the bivalent carrying the MLH1 focus indicated by the arrowhead. (D) Merged image of the MLH1, SYCP1 and REC8 signals; (E) the MLH1 signal; (F) the SYCP1 signal. (G,H) Cut out of panel C, showing the merged MLH1 and REC8 signals of chromosome 1 (G), and a reconstruction of chromosome 1, with REC8 represented in black and MLH1 in red (H). The arrow indicates an MLH1 focus at the crossing of cohesin axes of different bivalents; bivalent segments carrying such foci are excluded from the analysis. (I) Distributions of MLH1 foci along bivalents. Shown are the cumulative frequencies of MLH1 foci as a function of the distance to the centromeric end of the SC (wild type; black line) or cohesin axis (Sycp3/; red line). The distances are expressed as a percentage of the length of the SC (cohesin axis) on which the focus was. The numbers of foci on which the curves are based are shown in the upper left corners, and the chromosome numbers in the lower right corners of the graphs. Bars, 10 µm.
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© The Company of Biologists Ltd 2007