An X-linked GFP transgene reveals unexpected paternal X-chromosome activity in trophoblastic giant cells of the mouse placenta.
A GFP transgene has been integrated on the proximal part of the mouse X chromosome just distal of Timp and Syn1. During development, this X-linked GFP transgene exhibits widespread green fluorescence throughout the embryonic and adult life of male mice but displays mosaic expression in tissues as a result of X-inactivation in females. In living female embryos, inactivation of the transgene is imprinted in extraembryonic regions and random in the embryo proper, demonstrating that this reporter is behaving in a similar fashion to the majority of X-linked loci, and so provides a vital readout of X chromosome activity. This is observation is further supported in T16H/X female mice harboring the GFP transgene on the normal X chromosome where reporter inactivation is observed in somatic cells. The differential expression of GFP activity facilitates fluorescence activated cell sorting for the purification of GFP+ vs. GFP- cells from female embryonic tissues, thereby allowing access to populations of cells that have kept active a particular X chromosome. By tracking the activity of this X-linked GFP transgene, we discovered that the primary and secondary giant cells of the X/X placenta maintain an active paternal copy of this transgene on the presumed silenced paternal X-chromosome. This finding implies that the imprint on the paternal X chromosome may be relaxed in these trophectodermal derivatives.
Hadjantonakis
A K
AK
Cox
L L
LL
Tam
P P
PP
Nagy
A
A
D000818:Animals; D005260:Female; D018392:Genomic Imprinting; D015726:Giant Cells / Q000166:cytology; D049452:Green Fluorescent Proteins; D008164:Luminescent Proteins / Q000235:genetics*; D008297:Male; D051379:Mice; D010920:Placenta / Q000166:cytology; D062085:RNA, Long Noncoding; D022661:RNA, Untranslated / Q000235:genetics; D014157:Transcription Factors / Q000235:genetics; D019076:Transgenes; D014327:Trophoblasts / Q000166:cytology; D014960:X Chromosome
D008164:Luminescent Proteins; D062085:RNA, Long Noncoding; D022661:RNA, Untranslated; D014157:Transcription Factors; C077885:XIST non-coding RNA; D049452:Green Fluorescent Proteins