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Molecular and Cellular Biology, December 2009, p. 6245-6256, Vol. 29, No. 23
0270-7306/09/$08.00+0 doi:10.1128/MCB.00679-09
Copyright © 2009, American Society for Microbiology. All Rights Reserved.

Department of Pathology, Harvard Medical School, Boston, Massachusetts 02115,1 Whitehead Institute and Department of Biology, Massachusetts Institute of Technology, Cambridge, Massachusetts 02142,2 Department of Dentistry, School of Dentistry, National Yang-Ming University, Taipei, Taiwan3
Received 26 May 2009/ Returned for modification 18 June 2009/ Accepted 7 September 2009
The progression of spermatogenesis involves global changes in chromatin structure and conformation. However, our understanding of the regulation of chromatin changes in germ cells remains limited. Here we describe both in vivo RNA interference and genetic mouse knockout studies that identify a critical role for Yin Yang 1 (YY1) in mammalian spermatogenesis. In the YY1-deficient spermatocytes, we find a significant decrease in the global level of the heterochromatin markers (H3K9me3 and HP1-gamma) and a concomitant increase in the double-strand break (DSB) signals on chromosomes (gamma-H2AX, terminal deoxynucleotidyltransferase-mediated dUTP-biotin nick end labeling, and Rad51) at the leptotene/zygotene stages of spermatocytes. These findings support a link between chromatin modifications and meiotic DSB formation, as has been seen in other model organisms. We propose that a depletion of YY1 may alter the structural integrity of heterochromatin, rendering it more accessible to the DSB machinery. In addition, YY1-deficient spermatocytes show univalent formation, increased aneuploidy, and pachytene cell death, which are likely due to defects in DNA repair. Taken together, this study identifies an important role for YY1 in mouse meiosis and provides new insight into mechanisms that regulate mammalian spermatogenesis.
Published ahead of print on 28 September 2009.
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