Rsx is a metatherian RNA with Xist-like properties in X-chromosome inactivation.
In female (XX) mammals, one of the two X chromosomes is inactivated to ensure an equal dose of X-linked genes with males (XY). X-chromosome inactivation in eutherian mammals is mediated by the non-coding RNA Xist. Xist is not found in metatherians (marsupials), and how X-chromosome inactivation is initiated in these mammals has been the subject of speculation for decades. Using the marsupial Monodelphis domestica, here we identify Rsx (RNA-on-the-silent X), an RNA that has properties consistent with a role in X-chromosome inactivation. Rsx is a large, repeat-rich RNA that is expressed only in females and is transcribed from, and coats, the inactive X chromosome. In female germ cells, in which both X chromosomes are active, Rsx is silenced, linking Rsx expression to X-chromosome inactivation and reactivation. Integration of an Rsx transgene on an autosome in mouse embryonic stem cells leads to gene silencing in cis. Our findings permit comparative studies of X-chromosome inactivation in mammals and pose questions about the mechanisms by which X-chromosome inactivation is achieved in eutherians.
MRC National Institute for Medical Research, The Ridgeway, Mill Hill, London NW71AA, UK.
Jennifer
J
Grant
Shantha K
SK
Mahadevaiah
Pavel
P
Khil
Mahesh N
MN
Sangrithi
Hélène
H
Royo
Janine
J
Duckworth
John R
JR
McCarrey
John L
JL
VandeBerg
Marilyn B
MB
Renfree
Willie
W
Taylor
Greg
G
Elgar
R Daniel
RD
Camerini-Otero
Mike J
MJ
Gilchrist
James M A
JM
Turner
D000818:Animals; D005260:Female; D005786:Gene Expression Regulation; D020868:Gene Silencing; D051379:Mice; D048309:Monodelphis / Q000235:genetics* / Q000378:metabolism*; D012313:RNA / Q000235:genetics* / Q000378:metabolism*; D019076:Transgenes; D014960:X Chromosome / Q000235:genetics* / Q000378:metabolism*; D049951:X Chromosome Inactivation
D012313:RNA