We thank P. Burgoyne, P. Cohen, E. Alani, and P. Moens for helpful discussions, R. Viswanatha for helpful comments on the manuscript, W. Pawlowski and T. Pawlowska for input on the evolutionary tree of PCH2, R. Freire and J. Chen for antibodies, M. Jasin for Spo11 − embryonic stem cells, and R. Munroe for generating chimeric mice. We also thank an anonymous reviewer for pointing out that Pch2p might be sensing synaptic polymerization in yeast, not initiation. A previous version of this article appeared as an Early Online Release on June 21, 2007 (doi:10.1371/journal.pgen.0030130.eor).
Author contributions. XL and JCS conceived and designed the experiments and analyzed the data. XL performed the experiments. JCS wrote the paper.
Funding. This work was supported by NIH grant GM45415 to JS.
Competing interests. The authors have declared that no competing interests exist.
Abbreviations
CO crossover
DSB double strand break
MSCI meiotic sex chromosome inactivation
MSUC meiotic silencing of unpaired chromatin
NCO noncrossover
OA okadaic acid
RT-PCR reverse-transcriptase PCR
SC synaptonemal complex