The mouse X chromosome is enriched for multicopy testis genes showing postmeiotic expression.
According to the prevailing view, mammalian X chromosomes are enriched in spermatogenesis genes expressed before meiosis and deficient in spermatogenesis genes expressed after meiosis. The paucity of postmeiotic genes on the X chromosome has been interpreted as a consequence of meiotic sex chromosome inactivation (MSCI)--the complete silencing of genes on the XY bivalent at meiotic prophase. Recent studies have concluded that MSCI-initiated silencing persists beyond meiosis and that most genes on the X chromosome remain repressed in round spermatids. Here, we report that 33 multicopy gene families, representing approximately 273 mouse X-linked genes, are expressed in the testis and that this expression is predominantly in postmeiotic cells. RNA FISH and microarray analysis show that the maintenance of X chromosome postmeiotic repression is incomplete. Furthermore, X-linked multicopy genes exhibit a similar degree of expression as autosomal genes. Thus, not only is the mouse X chromosome enriched for spermatogenesis genes functioning before meiosis, but in addition, approximately 18% of mouse X-linked genes are expressed in postmeiotic cells.
Mueller
Jacob L
JL
Whitehead Institute, and Department of Biology, Massachusetts Institute of Technology, 9 Cambridge Center, Cambridge, Massachusetts 02142, USA. jmueller@wi.mit.edu
Mahadevaiah
Shantha K
SK
Park
Peter J
PJ
Warburton
Peter E
PE
Page
David C
DC
Turner
James M A
JM
D000818:Animals; D015342:DNA Probes; D018628:Gene Dosage; D018507:Gene Expression Regulation, Developmental; D050172:Genes, X-Linked / Q000235:genetics*; D017404:In Situ Hybridization, Fluorescence; D008297:Male; D008540:Meiosis / Q000235:genetics; D051379:Mice; D020411:Oligonucleotide Array Sequence Analysis; D015347:RNA Probes; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D020133:Reverse Transcriptase Polymerase Chain Reaction; D013091:Spermatogenesis / Q000235:genetics*; D013094:Spermatozoa / Q000378:metabolism*; D013737:Testis / Q000502:physiology*; D014960:X Chromosome / Q000235:genetics*
D015342:DNA Probes; D015347:RNA Probes; D012333:RNA, Messenger