McMahon, A. and Fosten, M. and Monk, M. (1983) X-chromosome inactivation mosaicism in the three germ layers and the germ line of the mouse embryo. Journal of Embryology and Experimental Morphology, 74 . pp. 207-220. ISSN 0022-0752. http://resolver.caltech.edu/CaltechAUTHORS:MCMjeem83
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Electrophoretic variant forms of the X-linked enzyme phosphoglycerate kinase (PGK-1, E.C.2, 7, 2, 3) have been used to examine X-chromosome mosaicism in tissues from 121/2-day post coitum heterozygous female mouse embryos. Samples of yolk-sac endoderm, neural ectoderm, heart (mesoderm), liver (endoderm) and germ cells were analysed from each embryo. In all tissues except yolk-sac endoderm, both PGK-1 isozymes were expressed. The extent of covariance among tissues with respect to the PGK-1 isozyme contribution is consistent with all tissues being derived from the same pool of cells after X-inactivation. The covariance among tissues gives an estimate of the size of this pool (47 cells) and places the earliest time of X-inactivation in epiblast cells between 41/2 and 51/2 days post coitum. From the independent variance among tissues within an individual, the average primordial precursor pool size for the three germ layers and the germ line itself was estimated as 193 cells.
|Additional Information:||© The Company of Biologists Ltd 1983. Accepted 1 November 1982. We are grateful to Prof M. Stone (Department of Statistical Science, University College London) for statistical help, to Prof T. Bücher (Institüt fur Physiologische Chemie, Munich) for instruction in PGK quantitation, and to Anne McLaren, M. Stone and P. Burgoyne for helpful discussion and critical comments on the manuscript.|
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|Deposited On:||12 Dec 2008 19:07|
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