International Mammalian Genome Society

17th International Mouse Genome Conference

9-12 November 2003, Braunschweig, Germany


Thorvaldsen J
University of Pennsylvania

Co-Authors: 2) Percec I, 3) Krapp C, 4) Singer E, 5) Nadeau J, 6) Willard H, 7) Bartolomei M
Institutions: 2) University of Pennsylvania, 3) University of Pennsylvania, 4) University of Pennsylvania, 5) Case Western Reserve University, 6) Duke University 7) HHMI and University of Pennsylvania

The mammalian epigenetic phenomena of X inactivation and genomic imprinting are incompletely understood. X inactivation equalizes X-linked expression between males and females by silencing genes on one X chromosome during female embryogenesis. Genomic imprinting functionally distinguishes the parental genomes resulting in parent-specific monoallelic expression of particular genes. N-ethyl-N-nitrosourea (ENU) mutagenesis was used in the mouse to screen for mutations in novel factors involved in X inactivation. Previously, we reported mutant pedigrees identified through this screen that segregate aberrant X inactivation phenotypes and we mapped the mutation in one pedigree to chromosome 15 (Science 296:1136). We now have mapped two additional mutations to the distal chromosome 5 and proximal chromosome 10 in a second pedigree and show that each of the mutations is sufficient to induce the mutant phenotype. We further show that the roles of these factors are specific to embryonic X inactivation as neither genomic imprinting of multiple genes nor imprinted X inactivation is perturbed. Lastly, we used mice bearing selected X-linked alleles that regulate X chromosome choice to demonstrate that the phenotypes of all three mutations are consistent with models in which the mutations have affected molecules involved specifically in the choice or initiation of X inactivation.

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