Department of Physiology and Cell Biology, University of Nevada School of Medicine, Reno, NV, USA.
Epigenetics. 2009 Oct 1;4(7):452-6. doi: 10.4161/epi.4.7.9923. Epub 2009 Oct 25.
Mammalian females have two X chromosomes, while males have only one X plus a Y chromosome. In order to balance X-linked gene dosage between the sexes, one X chromosome undergoes inactivation during development of female embryos. This process has been termed X-chromosome inactivation (XCI). Inactivation of the single X chromosome also occurs in the male, but is transient and is confined to the late stages of first meiotic prophase during spermatogenesis. This phenomenon has been termed meiotic sex chromosome inactivation (MSCI). A substantial portion ( approximately 15-25%) of X-linked mRNA-encoding genes escapes XCI in female somatic cells. While no mRNA genes are known to escape MSCI in males, approximately 80% of X-linked miRNA genes have been shown to escape this process. Recent results have led to the proposal that the RNA interference mechanism may be involved in regulating XCI in female cells. We suggest that some MSCI-escaping miRNAs may play a similar role in regulating MSCI in male germ cells.
哺乳动物的女性有两条 X 染色体，而男性只有一条 X 染色体加上一条 Y 染色体。为了平衡性别之间的 X 连锁基因剂量，女性胚胎发育过程中会有一条 X 染色体失活。这个过程被称为 X 染色体失活（XCI）。男性的单条 X 染色体也会失活，但这种失活是短暂的，仅限于精子发生过程中第一次减数分裂前期的晚期。这种现象被称为减数分裂性染色体失活（MSCI）。在女性体细胞中，大量（约 15-25%）的 X 连锁编码 mRNA 的基因逃避 XCI。虽然在男性中没有已知的 mRNA 基因逃避 MSCI，但约 80%的 X 连锁 miRNA 基因已被证明逃避了这一过程。最近的研究结果表明，RNA 干扰机制可能参与调节女性细胞中的 XCI。我们提出，一些逃避 MSCI 的 miRNA 可能在调节男性生殖细胞中的 MSCI 中发挥类似的作用。
