X-inactivation and the dynamic maintenance of gene silencing.
X-inactivation has long been a topic of fascination for educators, researchers, and clinicians alike. From complex patterns of inheritance to phenotypic variation among females with X-linked traits, a myriad of hypothesis and interpretations exist. Once thought to be random yet complete, X-inactivation has proven itself the poster child of the exception rather than the rule. Indeed, patterns of X-inactivation are all too often non-random, and many X-linked genes are capable of escaping X-inactivation. Similarly, X-inactivation is well-known for being stably maintained for life, but some previously inactivated X-linked genes reactivate with increasing age. Moreover, recent papers illustrate that X-inactivation can be challenged in other ways, thereby rendering the stability of X-inactivation compromised. This review describes factors involved in the maintenance of X-inactivation as we know it and discusses these emerging data that suggest a more dynamic model of the maintenance of X-inactivation may be in order.
Salstrom
Jennifer L
JL
Department of Human Genetics, David Geffen School of Medicine at UCLA, 6505 Gonda Center-Mail Code 708822, 695 Charles E Young Drive South, Los Angeles, CA 90095-708822, USA. jsalstrom@gmail.com
D041321:Chromosomes, Human, X / Q000235:genetics; D004303:Dosage Compensation, Genetic; D020868:Gene Silencing / Q000502:physiology*; D008040:Genetic Linkage; D006801:Humans; D049951:X Chromosome Inactivation / Q000502:physiology*