The pattern of X-chromosome inactivation in the embryonic and extra-embryonic tissues of post-implantation digynic triploid LT/Sv strain mouse embryos.
Spontaneously cycling LT/Sv strain female mice were mated to hemizygous Rb(X.2)2Ad males in order to facilitate the distinction of the paternal X chromosome, and the pregnant females were autopsied at about midday on the tenth day of gestation. Out of a total of 222 analysable embryos recovered, 165 (74.3%) were diploid and 57 (25.7%) were triploid. Of the triploids, 26 had an XXY and 31 an XXX sex chromosome constitution. Both embryonic and extra-embryonic tissue samples from the triploids were analysed cytogenetically by G-banding and by the Kanda technique to investigate their X-inactivation pattern. The yolk sac samples were separated enzymatically into their endodermally-derived and mesodermally-derived components, and these were similarly analysed, as were similar samples from a selection of control XmXp diploid embryos. In the case of the XmXmY digynic triploid embryos, a single darkly-staining Xm chromosome was observed in 485 (82.9%) out of 585, 304 (73.3%) out of 415, and 165 (44.7%) out of 369 metaphases from the embryonic, yolk sac mesodermally-derived and yolk sac endodermally-derived tissues, respectively. The absence of a darkly staining X-chromosome in the other metaphase spreads could either indicate that both X-chromosomes present were active, or that the Kanda technique had failed to differentially stain the inactive X-chromosome(s) present. In the case of the XmXmXp digynic triploid embryos, virtually all of the tissues analysed comprised two distinct cell lineages, namely those with two darkly-staining X-chromosomes, and those with a single darkly staining X-chromosome.(ABSTRACT TRUNCATED AT 250 WORDS)
Speirs
S
S
Department of Anatomy, University Medical School, Edinburgh, UK.
Cross
J M
JM
Kaufman
M H
MH
D000818:Animals; D002871:Chromosome Banding; D004303:Dosage Compensation, Genetic; D004622:Embryo, Mammalian / Q000502:physiology*; D047108:Embryonic Development; D005314:Embryonic and Fetal Development / Q000235:genetics; D005260:Female; D007621:Karyotyping; D008297:Male; D051379:Mice; D011123:Polyploidy; D011247:Pregnancy; D014960:X Chromosome