title: An enhancer element at the Igf2/H19 locus drives gene expression in both imprinted and non-imprinted tissues.
abstract: The insulin-like growth factor 2 (Igf2) gene encodes a potent growth factor that is expressed in multiple tissues during embryonic development. Expression at this locus is mediated by genomic imprinting. In the developing endodermal tissues, imprinting of Igf2 is mediated by the interaction of a set of enhancers downstream of the linked H19 gene with a differentially methylated domain (DMD) that lies approximately 2-4 kb upstream of H19 that has a boundary or insulator function in the hypomethylated state. In the remainder of tissues that express Igf2 and H19, the cis elements that drive their correct expression and imprinting are not well understood. In addition, enhancers driving expression of Igf2 in the choroid plexus and leptomeninges, tissues where the gene is thought not to be imprinted, have not been isolated. Here we show that biallelic (non-imprinted) expression within the choroid plexus is restricted to the epithelium, and we provide evidence that a conserved intergenic region functions as an enhancer for Igf2 both in tissues where the gene is imprinted, and where Igf2 is biallelically expressed. The presence of an enhancer for imprinted tissues in the intergenic region argues for the existence of imprinting controls distinct from the DMD, which may be provided by differential methylation at sites proximal to Igf2.
authors.affiliation: Developmental Biology Program, Department of Biology and Biochemistry, University of Bath, Bath, BA2 7AY, UK.
authors.forename: Marika
authors.initials: M
authors.lastname: Charalambous
authors.forename: Trevelyan R
authors.initials: TR
authors.lastname: Menheniott
authors.forename: William R
authors.initials: WR
authors.lastname: Bennett
authors.forename: Sharon M
authors.initials: SM
authors.lastname: Kelly
authors.forename: Ghislaine
authors.initials: G
authors.lastname: Dell
authors.forename: Luisa
authors.initials: L
authors.lastname: Dandolo
authors.forename: Andrew
authors.initials: A
authors.lastname: Ward
mesh_terms: D000818:Animals; D001483:Base Sequence; D002831:Choroid Plexus / Q000378:metabolism*; D017124:Conserved Sequence / Q000235:genetics; D003433:Crosses, Genetic; D019175:DNA Methylation; D017931:DNA Primers; D004742:Enhancer Elements, Genetic / Q000235:genetics*; D004848:Epithelium / Q000378:metabolism; D018507:Gene Expression Regulation, Developmental; D018392:Genomic Imprinting / Q000235:genetics*; D017403:In Situ Hybridization; D007335:Insulin-Like Growth Factor II / Q000235:genetics* / Q000378:metabolism; D007763:Lac Operon / Q000235:genetics; D051379:Mice; D008822:Mice, Transgenic; D008845:Microinjections; D019076:Transgenes
chemical_list: D017931:DNA Primers; D007335:Insulin-Like Growth Factor II