有袋类雄性生殖系中的性染色体沉默。
Sex chromosome silencing in the marsupial male germ line.
作者信息
Namekawa Satoshi H, VandeBerg John L, McCarrey John R, Lee Jeannie T
机构信息
Howard Hughes Medical Institute and Department of Molecular Biology, Massachusetts General Hospital, Harvard Medical School, Boston, MA 02114, USA.
出版信息
Proc Natl Acad Sci U S A. 2007 Jun 5;104(23):9730-5. doi: 10.1073/pnas.0700323104. Epub 2007 May 29.
In marsupials, dosage compensation involves silencing of the father's X-chromosome. Because no XIST orthologue has been found, how imprinted X-inactivation occurs is unknown. In eutherians, the X is subject to meiotic sex chromosome inactivation (MSCI) in the paternal germ line and persists thereafter as postmeiotic sex chromatin (PMSC). One hypothesis proposes that the paternal X is inherited by the eutherian zygote as a preinactive X and raises the possibility of a similar process in the marsupial germ line. Here we demonstrate that MSCI and PMSC occur in the opossum. Surprisingly, silencing occurs before X-Y association. After MSCI, the X and Y fuse through a dense plate without obvious synapsis. Significantly, sex chromosome silencing continues after meiosis, with the opossum PMSC sharing features of eutherian PMSC. These results reveal a common gametogenic program in two diverse clades of mammals and support the idea that male germ-line silencing may have provided an ancestral form of mammalian dosage compensation.
在有袋类动物中，剂量补偿涉及父本X染色体的失活。由于尚未发现XIST的直系同源物，印记X染色体失活是如何发生的尚不清楚。在真兽类动物中，X染色体在父本生殖系中经历减数分裂性染色体失活（MSCI），并在之后作为减数分裂后性染色质（PMSC）持续存在。一种假说认为，父本X染色体作为预失活的X染色体由真兽类动物的合子继承，并增加了有袋类动物生殖系中发生类似过程的可能性。在这里，我们证明了负鼠中发生了MSCI和PMSC。令人惊讶的是，失活发生在X-Y染色体联会之前。MSCI之后，X和Y通过一个没有明显联会的致密板融合。重要的是，减数分裂后性染色体沉默仍在继续，负鼠的PMSC具有真兽类动物PMSC的特征。这些结果揭示了两种不同哺乳动物分支中共同的配子发生程序，并支持了雄性生殖系沉默可能提供了哺乳动物剂量补偿的原始形式这一观点。
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