Genetic and Epigenetic Regulation of the CRH Gene in Pregnancy
Supervisor: Professor Rick Nicholson
CRH is a stress responsive hormone produced in the hypothalamus. CRH is also synthesised in the placenta and decidua. Placental production of CRH is linked to the determination of gestational length. Decidual expression of CRH is thought to be important in the regulation of implantation. In placental cells, CRH expression is stimulated by glucocorticoids while in the decidua and hypothalamus glucocorticoids inhibit expression.
Sequencing of the CRH gene indicates the presence of two common genetic haplotypes which mediate altered sensitivity to inflammatory responses. Abnormal production of CRH is observed in 45% of cases of preterm birth. Recent advances in the study of epigenetic gene regulation indicate that methylation of cytosine residues in the promoter and modifications of histones, particularly the H3 histone by acetylation or by methylation on the arginine (R) 2 residue or the lysine (4) residue, have profound effects on the tissue specific expression of genes.
In this project some students will study the different epigenetic regulation of the Corticotrophin Releasing Hormone (CRH) gene in the placenta, decidua and umbilical cord (which does not express CRH) to elucidate the epigenetic mechanisms regulating expression of this key gene, while other students will test the biological consequences of genetic polymorphisms of the CRH promoter with particular relevance to preterm birth. These studies will be performed in cell models of placenta and decidua as well as by using clinical samples from placenta, decidua and cord tissue. Students will have the opportunity to use histone deacetylase (HDAC) inhibitors, overexpression of HDAC proteins, chromatin immunoprecipitation (ChIP) for methylated and acetylated histones, methylation of DNA and key transcription factors, and Q-RT-PCR measurement of RNA. Reporter plasmids containing the common polymorphisms in the CRH promoter will be constructed and used to determine the effect of the polymorphisms both on chromatin and on the response to stimuli such as steroid hormones in transfected cells.
The extraordinary situation where three different human tissues, delivered at the same time, have three distinctly different patterns of specific gene expression provides an opportunity to study the epigenetic regulation of a gene that plays a central role in many biological processes.