International Mammalian Genome Society


The 13th International Mouse Genome Conference
October 31-November 3, 1999

Table of Contents * Structure * Bioinformatics * Sequence * Mapping * New Tools * Gene Discovery * Developmental * Mutagenesis * Functional Genomics

A16 Sequence Important for H19 and Igf2 Genomic Imprinting as Determined by Targeted Deletions in Mice

Joanne L. Thorvaldsen, Kristen L. Duran, Okechukwu Nwoko and Marisa S. Bartolomei. Howard Hughes Medical Institute, University of Pennsylvania, School of Medicine, Philadelphia, PA

We have demonstrated that differentially methylated sequence associated with the imprinted gene H19 controls genomic imprinting of H19 and the linked, oppositely-imprinted gene Igf2 (Genes & Development 12:3693). Specifically, a 2-kb-region located 5' to the imprinted mouse H19 gene is hypermethylated on the inactive paternal allele throughout development. We generated mice harboring a 1.6 kb targeted deletion of this differentially methylated domain (DMD) and assayed for allelic expression of H19 and Igf2. H19 is activated and Igf2 expression is reduced when the DMD deletion is paternally inherited; conversely, upon maternal transmission of the mutation, H19 expression is reduced and Igf2 is activated. Consistent with the DMD's hypothesized role of setting up the methylation imprint, the mutation also perturbs allele-specific methylation of the remaining H19 sequences. These experiments show that the H19 hypermethylated 5' flanking sequences are required to silence paternally-derived H19. Additionally, these experiments demonstrate a novel role for the DMD on the maternal chromosome where it is required for the maximal expression of H19 and the silencing of Igf2. Thus, the H19 differentially methylated sequences are required for both H19 and Igf2 imprinting. Repetitive elements associated with imprinted genes have also been proposed to control genomic imprinting. A sequence containing G-rich repeat elements (Grep) is located 3' of the DMD and 5' of the H19 promoter. The function of the Grep sequence is being tested in two separate targeted deletions that have been generated in mice: (1) a 2.9 kb deletion that removes both the DMD and Grep sequences; (2) a 1.3 kb deletion of only the Grep sequence. Comparative analysis of the mice harboring the 2.9 kb DMD/Grep, the 1.3 kb Grep and the 1.6 kb DMD deletions will be informative in further elucidating the requirements for H19 and Igf2 imprinted expression.

 


Abstracts * Officers * Bylaws * Application Form * Meeting Calendar * Contact Information * Home * Resources * News and Views * Membership

Base url http://imgs.org
Last modified: Saturday, November 3, 2012