Postmeiotic sex chromatin in the male germline of mice.
In mammals, the X and Y chromosomes are subject to meiotic sex chromosome inactivation (MSCI) during prophase I in the male germline, but their status thereafter is currently unclear. An abundance of X-linked spermatogenesis genes has spawned the view that the X must be active . On the other hand, the idea that the imprinted paternal X of the early embryo may be preinactivated by MSCI suggests that silencing may persist longer . To clarify this issue, we establish a comprehensive X-expression profile during mouse spermatogenesis. Here, we discover that the X and Y occupy a novel compartment in the postmeiotic spermatid and adopt a non-Rabl configuration. We demonstrate that this postmeiotic sex chromatin (PMSC) persists throughout spermiogenesis into mature sperm and exhibits epigenetic similarity to the XY body. In the spermatid, 87% of X-linked genes remain suppressed postmeiotically, while autosomes are largely active. We conclude that chromosome-wide X silencing continues from meiosis to the end of spermiogenesis, and we discuss implications for proposed mechanisms of imprinted X-inactivation.
Howard Hughes Medical Institute, Department of Molecular Biology, Massachusetts General Hospital, Boston, 02114, USA
Satoshi H
SH
Namekawa
Peter J
PJ
Park
Li-Feng
LF
Zhang
James E
JE
Shima
John R
JR
McCarrey
Michael D
MD
Griswold
Jeannie T
JT
Lee
D000818:Animals; D002843:Chromatin / Q000378:metabolism; D045584:Chromosome Positioning / Q000502:physiology*; D008297:Male; D008540:Meiosis / Q000502:physiology*; D051379:Mice; D020411:Oligonucleotide Array Sequence Analysis; D013087:Spermatids / Q000166:cytology / Q000648:ultrastructure; D013091:Spermatogenesis; D013094:Spermatozoa / Q000648:ultrastructure*; D014960:X Chromosome / Q000378:metabolism*; D049951:X Chromosome Inactivation / Q000502:physiology; D014998:Y Chromosome / Q000378:metabolism*
D002843:Chromatin