X-changing information on X inactivation.
In female somatic cells of mammalian species one X chromosome is inactivated to ensure dosage equality of X-encoded genes between females and males, during development and adulthood. X chromosome inactivation (XCI) involves various epigenetic mechanisms, including RNA mediated gene silencing in cis, DNA methylation, and changes in chromatin modifications and composition. XCI therefore provides an attractive paradigm to study epigenetic gene regulation in a more general context. The XCI process starts with counting of the number of X chromosomes present in a nucleus, and initiation of XCI follows if this number exceeds one per diploid genome. Recently, X-encoded RNF12 has been identified as a dose-dependent activator of XCI. In addition, other factors, including the pluripotency factors OCT4, SOX2 and Nanog, have been implicated to play a role in suppression of initiation of XCI. In this review, we highlight and explain these new and old findings in the context of a stochastic model for X chromosome counting and XCI initiation.
Barakat
Tahsin Stefan
TS
Department of Reproduction and Development, Room Ee 09-71, Erasmus MC, PO Box 2040, 3000 CA Rotterdam, The Netherlands.
Jonkers
Iris
I
Monkhorst
Kim
K
Gribnau
Joost
J
D000818:Animals; D019175:DNA Methylation; D044127:Epigenesis, Genetic; D005260:Female; D020868:Gene Silencing; D006801:Humans; D008297:Male; D013269:Stochastic Processes; D014157:Transcription Factors / Q000378:metabolism; D019076:Transgenes; D014960:X Chromosome / Q000502:physiology*; D049951:X Chromosome Inactivation
D014157:Transcription Factors