<p>Genomic imprinting is a phenomenon through which a subset of genes are epigenetically marked during gemtogenisis. This mark is maintained in the soma to often manifest parent of origin-specific monoalleleic expresson patterns. Genetics evidence suggests that gene expression patterns in mprinted genes, which are frequently organised in clusters, are regulated by the imprinting control regions (ICR). This thesis is mainly focused on the mechanisms through which the ICRs control the imprinting in the cluster, containing the <i>Kcnq1, Igf2</i> and <i>H19</i> genes, located at the distal end of mouse chromosome 7.</p><p>The <i>H19</i> ICR, located in the 5' flank of the <i>H19</i> gene represses paternal <i>H19</i> and maternal <i>Igf2</i> expression, respectively, but has no effect on <i>Kcnq1</i> expression, which is controlled by another ICR located at the intron 10 of the <i>Kcnq1</i> gene. This thesis demonstrates that the maternal <i>H19</i> ICR allele contains several DNase I hypersensitive sites, which map to target sites for the chromatin insulator protein CTCF at the linker regions between the positioned nucleosomes. The thesis demonstrates that the <i>H19</i> ICR acts as a unidirectional insulator and that this property invovles three nucleosome positioning sites facilitating interaction between the <i>H19</i> ICR and CTCF. The <i>Kcnq1</i> ICR function is much more complex, since it horbours both lineage-specific silencing functions and a methylation sensitive unidirectional chromatin insulator function. Importantly, the thesis demonstrates that the <i>Kcnq1</i> ICR spreads DNA methylation into flanking region only when it is itself unmethylated. Both the methylation spreading and silencing functions map to the same regions.</p><p>In conclusion, the thesis has unraveled and unrivalled complexity of the epigenetic control and function of short strtches of sequences. The epigenetic status of these cis elements conspires to control long-range silencing and insulation. The manner these imprinting control regions can cause havoc in expresson domains in human diseases is hence emerging.</p>
| Identifer | oai:union.ndltd.org:UPSALLA/oai:DiVA.org:uu-4002 |
| Date | January 2004 |
| Creators | Kanduri, Meena |
| Publisher | Uppsala University, Department of Animal Development and Genetics, Uppsala : Acta Universitatis Upsaliensis |
| Source Sets | DiVA Archive at Upsalla University |
| Language | English |
| Detected Language | English |
| Type | Doctoral thesis, comprehensive summary, text |
| Relation | Comprehensive Summaries of Uppsala Dissertations from the Faculty of Science and Technology, 1104-232X ; 941 |
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