X chromosome inactivation in clinical practice

Abstract

X chromosome inactivation (XCI) is the transcriptional silencing of the majority of genes on one of the two X chromosomes in mammalian females. Females are, therefore, mosaics for two cell lines, one with the maternal X and one with the paternal X as the active chromosome. The relative proportion of the two cell lines, the X inactivation pattern, may be analyzed by simple assays in DNA from available tissues. This review focuses on medical issues related to XCI in X-linked disorders, and on the value of X inactivation analysis in clinical practice.

X‐chromosome‐located microRNAs in immunity: Might they explain male/female differences?

“…Additionally, the mechanism of X-chromosome inactivation (XCI) (Box 1), which is expected to equilibrate the gene expression of females to that of males, is often incomplete and some genes may be expressed by both X chromosomes in female cells [14]. Not only is this phenomenon of silencing escape (Box 1) frequent [14], but also, females with extreme skewed XCI (Box 1) may never be affected by the disease for which they are carriers [15]. Numerous X-located genes have a direct or indirect role in immunity (reviewed in ref.…”

Mary Lyon og hypotesen om X-kromosominaktivering

“…De kvinnelige arvebaererne kan ha flekker av hud som mangler svettekjertler (9). X-kromosominaktiveringsmønsteret bestemmes i dag ved enkle PCR-baserte metoder og kan vaere til stor nytte i utredning av familier med arvelig sykdom (10).…”

Do we need a new look in the definition of X-linked recessive disorders?

“…At this point, the use of X chromosome inactivation tests is not current in clinical practice and may represent an additional diagnostic problem, since there are many variables that need to be considered in such analysis 13 . Therefore, as very well stated by Lourenço et al…”