The mouse X chromosome is enriched for multicopy testis genes showing postmeiotic expression

• DOI: 10.1038/ng.126
• Publication Date: 2008-05-05T06:13:46Z
• Authors: Jacob L Mueller; Shantha K Mahadev...; Peter J Park; Peter E Warburton; David C Page; James M A Turner
• Keywords: Male; X Chromosome; Reverse Transcriptase Polymerase Chain Reaction; Gene Dosage; Gene Expression Regulation, Developmental; RNA Probes; Spermatozoa; Article; Meiosis; Mice; Genes, X-Linked; Testis; Animals; RNA, Messenger; DNA Probes; Spermatogenesis; In Situ Hybridization, Fluorescence; Oligonucleotide Array Sequence Analysis

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.