Revisiting the consequences of deleting the X inactivation center
Hao Yin, Chunyao Wei, Jeannie T. Lee
Abstract
Significance Mammalian cells equalize X-linked dosages between the male (XY) and female (XX) sexes by silencing one X chromosome in the female sex. X chromosome inactivation (XCI) requires the X inactivation center ( Xic ), which spans several hundred kilobases in the mouse and includes several required noncoding genes. Over three decades, transgenic and deletional analyses have demonstrated that the Xic is both necessary and sufficient to induce X chromosome counting, choice, and the initiation of whole-chromosome silencing. However, one recent study reported that deleting the noncoding Xic surprisingly had no effect on counting or initiation of XCI. Here, we revisited the question, created independent Xic deletion lines, and reaffirmed the essential nature of the Xic for counting and X chromosome silencing.