International Mammalian Genome Society

A7 Characterisation of a Putative Imprinting Control Element Which Lies Between the Imprinted Igf2 and H19 Genes in the Mouse

Marika Charalambous and A. Ward. School of Biology and Biochemistry, University of Bath, Bath, UK

A DNaseI hypersensitive, hypomethylated region lies midway between the oppositely imprinted Igf2 and H19 genes. The region is conserved in a variety of mammalian species and may contain novel imprinting control elements and/or tissue specific enhancers. This study aims to characterise this intergenic region by utilising a panel of transgenic mice bearing putative and known Igf2/H19 control elements fused in-cis with the reporter gene firefly luciferase.

Luciferase assays performed on neonatal transgeneic mice have revealed that this region can drive reporter gene expression in the brain, gene expression is concentrated in the exchange tissues. Igf2 is expressed biallelically from the exchange tissues throughout development and adult life.

A tissue culture system; primary culture of cells derived from mouse choroid plexus, has been set up in order to dissect the function of this element in vitro. A choroid plexus cell line is also being established by culturing cells from p53 knock-out mice.

This cell line may form a model system in which to study how Igf2 manages to escape the imprinting mechanism, giving rise to biallelic expression of this gene in the choroid plexus and leptomeninges of the brain.

The intergenic region provides a candidate locus for factors that are able to override the imprinting signal.