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- Garnett-Powers & Associates - Postdoctoral Insurance Plan on 2009-11-19
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10.1007/s00335-005-0059-2 on 2009-11-17
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X-inactivation patterns are known to be relatively consistent within the tissues of an individual mouse, but do vary slightly
(Nesbitt 1971; Johnston and Cattanach 1981; Krietsch et al. 1986; Plenge et al. 2000) because each tissue is derived from an independent sampling event in progenitor cells. We considered the possibility that
sampling whole-embryo RNA rather than adult tissue samples could reduce the variation in X-inactivation patterns observed
not directly attributable to the initial choice between chromosomes, making them a more suitable system for studies of X chromosome
choice. To test this hypothesis, we compared the X-inactivation patterns of F1 adults to those of F1 embryos. As shown in Fig. 4B, the distribution of X-inactivation patterns in F1 whole embryos was significantly tighter than we observed in the F1 adult ear biopsies; the mean did not change significantly, but the variance was significantly reduced in the whole embryos
(F-test p = 0.007). Although this finding may not be surprising given that the whole embryo is a more representative sample than a
specific tissue with respect to X inactivation, it does suggest that embryos may be an ideal system for future studies of
X chromosome choice.
Estimating precursor cell population from whole embryos
The variance observed in X-inactivation patterns can be used to estimate the approximate number of cells present at the time
of X chromosome choice, as in previous studies (McMahon et al. 1983; Baader et al. 1996). The whole-embryo data are a useful sample with which to readdress this question because the variance in patterns is attributed
to just one sampling event (choosing between the two chromosomes), rather than two (choosing a subset of X-inactivated cells
that will then give rise to the tissue in question). Using an approach outlined previously (McMahon et al. 1983; see Materials and methods), we used the F1 whole-embryo data to determine the number of precursor cells present. Our data indicate that approximately 70 cells were
present at the initial choice (95% CI, 48–96 cells), suggesting that X chromosome choice in the cells of the embryo proper
occurs between 4.5 and 5.5 days post coitum, in agreement with previous estimates (Monk and Harper 1979; Rastan et al. 1980; McMahon et al. 1983; McMahon and Monk 1983; Baader et al. 1996)
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sebastien_vigneau on 2009-11-17
Discussion about secondary skewing and clonality in random X-chromosome inactivation, with an estimate of the number of cells when random X-inactivation is initiated.
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- Mouse Husbandry, Breeding and Development on 2009-11-05
- mount_fstab - Documentation Ubuntu Francophone on 2009-11-05
- Basic vi Commands on 2009-11-03
- Partitioning/Home/Moving - Community Ubuntu Documentation on 2009-11-03
- Wuala Blog: Effective Usage: Wuala on Ubuntu on 2009-11-02
- Molecular Expressions Microscopy Primer: Anatomy of the Microscope - Numerical Aperture and Resolution on 2009-10-29
- Upgrading to Ubuntu 8.10 - Community Ubuntu Documentation on 2009-10-24
- iheartlinux.com » Basic IPtables Configuration on 2009-10-23
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Philadelphia
1 members, 1 items
Events and must-see in Philadelphia.<br />History of the birth-place of America.
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