The imprinting centre 2 (IC2) on mouse distal chromosome 7 is part of a cluster of genes of which ten are currently known to be monoallelically expressed. All genes in the cluster are paternally silenced, with the exception of the non-coding RNA gene <i>Kcnqlot1</i>, which is maternally silenced. In this study I have been interested to understand how and when allelic expression and allelic histone marks are established in the IC2 cluster, and how they are erased in germ cells. I have used trophoblast stem (TS) and trophoblast giant cells as a model system of placental development to determine lineage specific histone modifications and gene expression. Using this model system, I was able to show that placental allele specific histone modifications are established after the blastocyst stage. Using a mutant for an oocyte-specific form of Dnmt1 (Dnmtlo), I have analysed imprinted expression and levels of transcription of genes in the cluster. This has allowed me to identify a particular time point during development from which expression of <i>Kcnqlot1</i> can target gene silencing and repressive histone marks in <i>cis </i>to the imprinted genes in the cluster. Finally, I was interested to see if histone marks associated with imprinting are removed during the process of imprint erasure in primordial germ cells (PGCs). To this end I have developed a sensitive chromatin immunoprecipitation (ChIP) technique that can be used in combination with single strand conformational polymorphism (SSCP). This method enabled me to investigate allele specific histone modifications in small numbers of cells (10<sup>3</sup>-10<sup>4</sup>). This has allowed me to show that some allele specific histone modifications remain in primordial germ cells (PGCs) at the IC2 cluster after DNA methylation has been erased at E13.5.
| Identifer | oai:union.ndltd.org:bl.uk/oai:ethos.bl.uk:599642 |
| Date | January 2006 |
| Creators | Green, K.-A. |
| Publisher | University of Cambridge |
| Source Sets | Ethos UK |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
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