Loss of imprinting at the <it>Dlk1</it>-<it>Gtl2 </it>locus caused by insertional mutagenesis in the <it>Gtl2 </it>5' region

• Main Authors: Appelbe Oliver K, Yevtodiyenko Aleksey, Glick Elena A, Carr Michael S, Steshina Ekaterina Y, Schmidt Jennifer V
• Format: Article
• Language: English
• Published: BMC 2006-10-01
• Series: BMC Genetics
• Online Access: http://www.biomedcentral.com/1471-2156/7/44

<p>Abstract</p> <p>Background</p> <p>The <it>Dlk1 </it>and <it>Gtl2 </it>genes define a region of mouse chromosome 12 that is subject to genomic imprinting, the parental allele-specific expression of a gene. Although imprinted genes play important roles in growth and development, the mechanisms by which imprinting is established and maintained are poorly understood. Differentially methylated regions (DMRs), which carry methylation on only one parental allele, are involved in imprinting control at many loci. The <it>Dlk1</it>-<it>Gtl2 </it>region contains three known DMRs, the <it>Dlk1 </it>DMR in the 3' region of <it>Dlk1</it>, the intergenic DMR 15 kb upstream of <it>Gtl2</it>, and the <it>Gtl2 </it>DMR at the <it>Gtl2 </it>promoter. Three mouse models are analyzed here that provide new information about the regulation of <it>Dlk1</it>-<it>Gtl2 </it>imprinting.</p> <p>Results</p> <p>A previously existing insertional mutation (<it>Gtl2lacZ</it>), and a targeted deletion in which the <it>Gtl2 </it>upstream region was replaced by a <it>Neo </it>cassette (<it>Gtl2Δ5'Neo</it>), display partial lethality and dwarfism upon paternal inheritance. Molecular characterization shows that both mutations cause loss of imprinting and changes in expression of the <it>Dlk1</it>, <it>Gtl2 </it>and <it>Meg8</it>/<it>Rian </it>genes. <it>Dlk1 </it>levels are decreased upon paternal inheritance of either mutation, suggesting <it>Dlk1 </it>may be causative for the lethality and dwarfism. Loss of imprinting on the paternal chromosome in both <it>Gtl2lacZ </it>and <it>Gtl2Δ5'Neo </it>mice is accompanied by the loss of paternal-specific <it>Gtl2 </it>DMR methylation, while maternal loss of imprinting suggests a previously unknown regulatory role for the maternal <it>Gtl2 </it>DMR. Unexpectedly, when the <it>Neo </it>gene is excised, <it>Gtl2Δ5' </it>animals are of normal size, imprinting is unchanged and the <it>Gtl2 </it>DMR is properly methylated. The exogenous DNA sequences integrated upstream of <it>Gtl2 </it>are therefore responsible for the growth and imprinting effects.</p> <p>Conclusion</p> <p>These data provide further evidence for the coregulation of the imprinted <it>Dlk1 </it>and <it>Gtl2 </it>genes, and support a role for <it>Dlk1 </it>as an important neonatal growth factor. The ability of the <it>Gtl2lacZ </it>and <it>Gtl2Δ5'Neo </it>mutations to cause long-range changes in imprinting and gene expression suggest that regional imprinting regulatory elements may lie in proximity to the integration site.</p>