The role on imprinting of the human IGF2R gene in oncogenesis

The mouse Igf2r gene is expressed only from the maternal chromosome in the embryo. The gene contains an intronic CpG island named the "Igf2r imprinting box" which has previously been shown to carry a maternal- specific methylation mark (Stöger et al. 1993). We have identified a second transcript from the same locus which is however expressed only from the paternal allele and oriented in the opposite direction to the Igf2r mRNA. The promoter of this antisense transcript is associated with the intronic `Igf2r imprinting box` and the transcript does not apparently encode for a protein. The discovery of an imprinted, non-coding transcript at the Igf2r locus which is inversely correlated with the presence of Igf2r mRNA in cis, suggests parallels to the imprinted Igf2/H19 system or to the Xist transcript which is responsible for inactivating one of the two X chromosomes in females In the course of the first 10 month of this project, allele-specificity of this novel antisense (AS-) transcript was established and transcription initiation sites were mapped. Furthermore a characterization of the extent of the RNA and measurement of its transcription rate have been initiated. Additionally, an RNA-FISH assay has been established (in collaboration with Dr. G. Braidotti) in order to analyze allelic expression and transcriptional activity of the `promotor at the single cell level as well as subcellular RNA localization. The goals for the continuation of this project have not been significantly changed and are summarized as follows (see also initial fellowship application; February 1996): (1) Proof of continuity/mapping of the AS-transcript (2) sequencing, (3) transcriptional activity of the As-promotor and (4) subcellular localization of the Igf2r antisense transcript.