Dosage compensation and gene expression on the mammalian X chromosome: one plus one does not always equal two.
Dosage compensation and gene expression on the mammalian X chromosome: one plus one does not always equal two.
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DOI：
10.1007/s10577-009-9063-9
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发表时间：
2009
期刊：
影响因子：
--
通讯作者：
Carrel L
中科院分区：
文献类型：
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作者：
Prothero KE;Stahl JM;Carrel L
计算染色体不只是简单的数学。尽管正常男性和女性的性染色体含量不同（XY vs. XX），但X染色体失衡是可以容忍的，因为剂量补偿机制已经进化到确保功能对等。在哺乳动物中，这是通过两个过程完成的：X染色体失活使雌性X染色体上的大多数基因沉默，导致两性中大多数基因的功能X单体；X染色体上调导致雄性和雌性单个活性X染色体上的基因表达增加，相对于常染色体的剂量相等。本文主要综述了X染色体上的基因，以及这两个过程如何影响基因的含量、组织和表达水平。特别要注意的是那些没有X灭活的基因，它们不一定是完全剂量补偿的。这些“逃避”X失活的基因在医学上具有重要意义，因为它们解释了性染色体非整倍体个体的表型，并可能影响男性和女性之间的正常特征和疾病。此外，逃逸基因对X染色体失活如何在X染色体上传播和维持提供了深入的了解。
Counting chromosomes is not just simple math. Although normal males and females differ in sex chromosome content (XY vs. XX), X chromosome imbalance is tolerated because dosage compensation mechanisms have evolved to ensure functional equivalence. In mammals this is accomplished by two processes—X chromosome inactivation that silences most genes on one X chromosome in females, leading to functional X monosomy for most genes in both sexes, and X chromosome upregulation that results in increased gene expression on the single active X in males and females, equalizing dosage relative to autosomes. This review focuses on genes on the X chromosome, and how gene content, organization and expression levels can be influenced by these two processes. Special attention is given to genes that are not X inactivated, and are not necessarily fully dosage compensated. These genes that “escape” X inactivation are of medical importance as they explain phenotypes in individuals with sex chromosome aneuploidies and may impact normal traits and disorders that differ between men and women. Moreover, escape genes give insight into how X chromosome inactivation is spread and maintained on the X.