Danielle Bourque

“Imprinted Genes in the Placenta and Obstetrical Complications”

BSc. (Honours), Dalhousie University, 2006

Date & time: Monday, May 31, 2010, noon

Exam location: D312, Shaughnessy Builiding, BC Children’s and Women’s Hospital, 4500 Oak Street, Vancouver, BC

ABSTRACT

Each year, many pregnancies are associated with obstetrical complications such as maternal pre-eclampsia (PET) and fetal intrauterine growth restriction (IUGR). Poor placentation is thought to contribute to these complications, but specific causes are largely unknown. Mouse models suggest that epigenetic mechanisms, in particular genomic imprinting, that alter gene regulation may help regulate placental development and embryonic growth. The first goal of this thesis is to examine if epigenetic modifications (i.e. DNA methylation) and altered expression of imprinted genes in the human placenta are contributing factors to PET and IUGR. The second goal of this thesis is to identify imprinted loci that are useful in the diagnosis of placental pathologies that associated with abnormal imprinting, including triploidy, hydatidiform moles, and placental mesenchymal dysplasia.

I found that DNA methylation at the imprinting control region 1 (ICR1) on chromosome 11p15.5 was significantly decreased in IUGR placentas (p < 0.001), but not in those associated with pre-eclampsia. Methylation at ICR2 (KvDMR1) was not significantly altered in PET or IUGR. No significant changes in expression levels were observed in the genes controlled by these ICRs. There were no significant methylation changes observed in any candidate imprinted gene evaluated by the Illumina array. LINE-1 methylation, a marker of whole genome methylation, was also similar in all groups. The establishment of biomarkers that could be used to accurately identify those women at an increased risk for pre-eclampsia or IUGR would be a major step forward in antenatal care.

All placental pathologies (triploidy, hydatidiform moles or placental mesenchymal dysplasia) were associated with altered ICR2 (KvDMR1) methylation. Pyrosequencing assays for SGCE, SNRPN, and MEST were also compared for their utility in diagnosing parental imbalance in placental samples. SGCE showed the clearest separation between groups. The combined use of KvDMR1 and SGCE assays could provide a potentially valuable diagnostic tool in the rapid screening of methylation errors in placental disorders. These results also demonstrate the maintenance of imprinting status at these loci in the human placenta, even in the presence of abnormal pathology.

EXAMINING COMMITTEE

Chair: Dr. Jan Friedman (Medical Genetics)

Supervisory Committee: Dr. Wendy P. Robinson, Research Supervisor (Medical Genetics) & Dr. Louis Lefebvre (Medical Genetics)

University Examiner: Dr. Evica Rajcan-Separovic (Pathology, Medical Genetics)

SUPERVISORY COMMITTEE

Dr. Wendy P. Robinson, Research Supervisor (Medical Genetics), Dr. Louis Lefebvre (Medical Genetics) & Dr. Sylvie Langlois (Medical Genetics)

PUBLICATIONS

DK Bourque, L Avila, M Peñaherrera, P von Dadelszen, WP Robinson. Decreased placental methylation at the H19/IGF2 imprinting control region is associated with normotensive intrauterine growth restriction but not preeclampsia. Placenta 2010; 31:197-202.

DK Bourque, MS Peñaherrera, RKC Yuen, MA van Allen, DE McFadden, WP Robinson. The utility of quantitative methylation assays at imprinted genes for the diagnosis of fetal and placental disorders. Accepted to Clinical Genetics 2010.

SELECTED PRESENTATIONS

American Society of Human Genetics Meeting. Philadelphia, PA, November 2008. Poster Presentation. “A Pyrosequencing assay to rapidly and quantitatively assess methylation at KvDMR1”

International Federation of Placenta Associations 2008 Conference. Seggau Castle, Austria, September 2008. Poster Presentation. “11p15.5 imprinted gene methylation and expression patterns in placentas from complicated pregnancies”

15th Western Perinatal Research Meeting. Banff, AB, February 2008. Poster Presentation. “Imprinted gene methylation and expression patterns in placentas from complicated pregnancies”

American Society of Human Genetics Meeting. San Diego, CA, October 2007. Poster Presentation. “Hypomethylation at the H19/IGF2 ICR1 in the human placenta is associated with fetal intrauterine growth restriction”

14th Western Perinatal Research Meeting. Banff, AB, February 2007. Poster Presentation. “Hypomethylation of the H19/IGF2 ICR1 is associated with fetal growth restriction”

AWARDS

2008 CFRI Trainee Travel Award

2008 Y.W. Loke New Investigator Travel Award

2007-2009 MSFHR: Junior Graduate Studentship

2007-2008 CIHR Research Canada Graduate Scholarships: Master’s Award

2007 Medical Genetics Research Day Junior Poster Prize

2007 CIHR Institute of Human Development, Child and Youth Health Travel Award

2007 Interdisciplinary Women’s Reproductive Health Program Trainee Award

2007 CFRI Trainee Travel Award

2006 UBC Medical Genetics Graduate Entrance Scholarship

GRADUATE STUDIES

Area of research: Medical Genetics

Courses:

MEDG 419: Human Cytogenetics, Dr. Carolyn Brown

MEDG 505: Genome Analysis, Dr. Steven Jones

MEDG 520: Advances in Human Molecular Genetics, Dr. Rob McMaster

MEDG 530: Human Genetics, Dr. Lorne Clark

MEDG 545: Current Topics in Medical Genetics Research, Dr. Carolyn Brown

MEDG 548: Directed Studies, Dr. Wendy Robinson

OBST 502: Maternal and Fetal Physiology, Dr. Dan Rurak

SPPH 537: Perinatal Epidemiology, Dr. Patricia Janssen

Danielle Bourque- MSc programme (pdf)