Dynamic histone modifications mark sex chromosome inactivation and reactivation during mammalian spermatogenesis
- *Division of Pediatrics Genetics and Center for Mammalian Genetics and †Department of Molecular Genetics and Microbiology, Interdisciplinary Program in Genetics, University of Florida College of Medicine, Gainesville, FL 32610
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Edited by Stanley M. Gartler, University of Washington, Seattle, WA, and approved October 8, 2004 (received for review August 27, 2004)
Abstract
Based on the formation of the XY body at pachytene and expression studies of a few X-linked genes, the X and Y chromosomes seem to undergo transcriptional inactivation during mammalian spermatogenesis. However, the extent and the mechanism of X and Y inactivation are not known. Here, we show that both the X and Y chromosomes undergo sequential changes in their histone modifications beginning at the pachytene stage of meiosis. These changes usually are associated with transcriptional inactivation in somatic cells, and they coincide with the exclusion of the phosphorylated (active) form of RNA polymerase II from the XY body. Both sex chromosomes undergo extensive deacetylation at histones H3 and H4 and (di)methylation of lysine (K)9 on histone H3; however, there are no changes in H3–K4 methylation. These changes persist even when the XY body disappears in late pachytene, and the X and Y chromosomes segregate from one another after the first meiotic division. By the spermatid stage, histone modifications of the X and Y chromosomes revert to those of active chromatin and RNA polymerase II reengages with both chromosomes. Our observations indicate that X and Y inactivation is extensive and persists even when the X and Y chromosomes are separated in secondary spermatocytes. These findings provide insights into epigenetic programming and chromatin dynamics in the male germ line.
Footnotes
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↵ § To whom correspondence should be addressed at: Division of Pediatrics Genetics, Box 100296, University of Florida College of Medicine, Gainesville, FL 32610-0296. E-mail: driscdj{at}peds.ufl.edu.
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↵ ‡ Present address: Quest Diagnostics, 33608 Ortega Highway, San Juan Capistrano, CA 92690-6130.
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Author contributions: A.M.K., F.Z.B., and D.J.D. designed research; A.M.K. and F.Z.B. performed research; A.M.K. and D.J.D. analyzed data; and A.M.K. and D.J.D. wrote the paper.
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This paper was submitted directly (Track II) to the PNAS office.
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Abbreviations: XYi, X and Y inactivation; Xi, X inactivation.
- Copyright © 2004, The National Academy of Sciences
