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Cow clones

Jonathan B Weitzman

Genome Biology 2002, 3:spotlight-20020529-01  doi:10.1186/gb-spotlight-20020529-01

The electronic version of this article is the complete one and can be found online at:

Published:29 May 2002

© 2002 BioMed Central Ltd

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X-chromosome inactivation, the largest epigenetic event known, involves random silencing of one of the two X chromosomes in the cells of female mammals. In an Advanced Early Publication in Nature Genetics, Xue et al. report defects in X inactivation in cells from cloned bovine embryos (Nature Genetics, 18 May 2002, DOI:10.1038/ng900). They looked at the allele-specific expression of the X-linked monoamine oxidase type A (MAOA) gene and at the expression of Xist and other X-linked genes in cloned XX calves. They found evidence for aberrant X-chromosome inactivation in deceased clones, and incomplete nuclear reprogramming. Xue et al. show that X-chromosome inactivation is paternally imprinted in extra-embryonic tissues of normal cows, but is random in the placentae of deceased clones. The defective patterns of X inactivation seen in cloned cows are in contrast to the normal X inactivation events reported in cloned mice.


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