X-Chromosome inactivation in cloned mouse embryos.
To study whether cloning resets the epigenetic differences between the two X chromosomes of a somatic female nucleus, we monitored X inactivation in cloned mouse embryos. Both X chromosomes were active during cleavage of cloned embryos, followed by random X inactivation in the embryo proper. In the trophectoderm (TE), X inactivation was nonrandom with the inactivated X of the somatic donor being chosen for inactivation. When female embryonic stem cells with two active X chromosomes were used as donors, random X inactivation was seen in the TE and embryo. These results demonstrate that epigenetic marks can be removed and reestablished on either X chromosome during cloning. Our results also suggest that the epigenetic marks imposed on the X chromosomes during gametogenesis, responsible for normal imprinted X inactivation in the TE, are functionally equivalent to the marks imposed on the chromosomes during somatic X inactivation.
Eggan
K
K
Whitehead Institute for Biomedical Research and Department of Biology, Massachusetts Institute of Technology, 9 Cambridge Center, Cambridge, MA 02142, USA.
Akutsu
H
H
Hochedlinger
K
K
Rideout
W
W
Yanagimachi
R
R
Jaenisch
R
R
D000483:Alleles; D000818:Animals; D002454:Cell Differentiation; D019976:Cloning, Organism; D004303:Dosage Compensation, Genetic; D004622:Embryo, Mammalian / Q000166:cytology / Q000378:metabolism*; D005314:Embryonic and Fetal Development; D005260:Female; D020868:Gene Silencing; D017930:Genes, Reporter; D018392:Genomic Imprinting; D049452:Green Fluorescent Proteins; D008164:Luminescent Proteins / Q000235:genetics; D008297:Male; D051379:Mice; D009115:Muridae; D053652:Nuclear Transfer Techniques; D009865:Oocytes; D010920:Placenta / Q000378:metabolism; D020133:Reverse Transcriptase Polymerase Chain Reaction; D033581:Stem Cell Transplantation; D013234:Stem Cells / Q000378:metabolism; D019076:Transgenes; D014960:X Chromosome / Q000235:genetics* / Q000378:metabolism
D008164:Luminescent Proteins; D049452:Green Fluorescent Proteins