An X-linked GFP transgene reveals unexpected paternal X-chromosome activity in trophoblastic giant cells of the mouse placenta

Genesis. 2001 Mar;29(3):133-40. doi: 10.1002/gene.1016.


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.

Publication types

  • Letter
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Female
  • Genomic Imprinting*
  • Giant Cells* / cytology
  • Green Fluorescent Proteins
  • Luminescent Proteins / genetics*
  • Male
  • Mice
  • Placenta / cytology
  • RNA, Long Noncoding
  • RNA, Untranslated / genetics
  • Transcription Factors / genetics
  • Transgenes
  • Trophoblasts* / cytology
  • X Chromosome*


  • Luminescent Proteins
  • RNA, Long Noncoding
  • RNA, Untranslated
  • Transcription Factors
  • XIST non-coding RNA
  • Green Fluorescent Proteins