TY - JOUR
T1 - When the lyon(Ized chromosome) roars
T2 - Ongoing expression from an inactive X chromosome
AU - Carrel, Laura
AU - Brown, Carolyn J.
N1 - Publisher Copyright:
© 2017 The Author(s) Published by the Royal Society. All rights reserved.
PY - 2017/11/5
Y1 - 2017/11/5
N2 - A tribute to Mary Lyon was held in October 2016. Many remarked about Lyon’s foresight regarding many intricacies of the X-chromosome inactivation process. One such example is that a year after her original 1961 hypothesis she proposed that genes with Y homologues should escape from X inactivation to achieve dosage compensation between males and females. Fifty-five years later we have learned many details about these escapees that we attempt to summarize in this review, with a particular focus on recent findings. We now know that escapees are not rare, particularly on the human X, and that most lack functionally equivalent Y homologues, leading to their increasingly recognized role in sexually dimorphic traits. Newer sequencing technologies have expanded profiling of primary tissues that will better enable connections to sex-biased disorders as well as provide additional insights into the X-inactivation process. Chromosome organization, nuclear location and chromatin environments distinguish escapees from other X-inactivated genes. Nevertheless, several big questions remain, including what dictates their distinct epigenetic environment, the underlying basis of species differences in escapee regulation, how different classes of escapees are distinguished, and the roles that local sequences and chromosome ultrastructure play in escapee regulation. This article is part of the themed issue ‘X-chromosome inactivation: a tribute to Mary Lyon’.
AB - A tribute to Mary Lyon was held in October 2016. Many remarked about Lyon’s foresight regarding many intricacies of the X-chromosome inactivation process. One such example is that a year after her original 1961 hypothesis she proposed that genes with Y homologues should escape from X inactivation to achieve dosage compensation between males and females. Fifty-five years later we have learned many details about these escapees that we attempt to summarize in this review, with a particular focus on recent findings. We now know that escapees are not rare, particularly on the human X, and that most lack functionally equivalent Y homologues, leading to their increasingly recognized role in sexually dimorphic traits. Newer sequencing technologies have expanded profiling of primary tissues that will better enable connections to sex-biased disorders as well as provide additional insights into the X-inactivation process. Chromosome organization, nuclear location and chromatin environments distinguish escapees from other X-inactivated genes. Nevertheless, several big questions remain, including what dictates their distinct epigenetic environment, the underlying basis of species differences in escapee regulation, how different classes of escapees are distinguished, and the roles that local sequences and chromosome ultrastructure play in escapee regulation. This article is part of the themed issue ‘X-chromosome inactivation: a tribute to Mary Lyon’.
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U2 - 10.1098/rstb.2016.0355
DO - 10.1098/rstb.2016.0355
M3 - Review article
C2 - 28947654
AN - SCOPUS:85030167465
SN - 0962-8436
VL - 372
JO - Philosophical Transactions of the Royal Society B: Biological Sciences
JF - Philosophical Transactions of the Royal Society B: Biological Sciences
IS - 1733
M1 - 20160355
ER -