Jenna Plamondon
Genetic and Epigenetic Factors in a Mouse Model for Multifactorial Cleft
Lip
Friday, September 3, 2010,
10:00 am. Room 1416, Life Sciences Centre, 2350 Health Sciences Mall, UBC
Campus
Jenna Plamondon- Defense Programme (pdf)
EXAMINING COMMITTEE
Chair: Dr. Elizabeth Simpson
(Medical Genetics)
Supervisory Committee: Dr. Diana
Juriloff, Research Supervisor (Medical Genetics) & Dr. Dixie Mager (Medical
Genetics)
University Examiner: Dr.
Carolyn Brown (Medical Genetics)
SUPERVISORY COMMITTEE
Dr. Muriel Harris & Dr.
Joy Richman
Cleft lip (CL/P) is a human birth
defect with complex genetic etiology. Two loci are involved in CL/P in the A/WySn mouse
model: Wnt9b on chromosome 11 and clf2
on chromosome 13. There are
two known mutant alleles at Wnt9b; clf1
is a spontaneous recessive mutation caused by an insertion of an IAP transposon
near the gene Wnt9b and the second
allele is a Wnt9b knock out. Clf2
is the second locus required for the CL/P phenotype.
Quantitative PCR was used to
investigate expression of other genes that might be affected by the absence of Wnt9b expression. Expression levels of Bmp4, Dkk1, Msx1, Msx2, Raldh3, Sox11, Wnt3,
Wnt4 and b-catenin were examined. This
experiment detected a significant decrease in expression levels of b-catenin in Wnt9bNull/Null
embryos.
The clf2 gene has not yet been identified and the function was unknown.
Segregants from multi-generation crosses using the Wnt9b knockout, “Cross 1” and “Cross 2”,
were examined for CL/P and genotype at polymorphic markers linked to Wnt9b and clf2 to ask whether clf2
modifies the frequency of CL in the Wnt9b
null homozygotes. I also used
recombinants from a congenic stock, consulted the mouse genome assembly and
examined ancestral haplotypes in a strain survey to define the clf2 candidate region and examined mouse
genome databases to develop a candidate gene list.
My studies have reduced the clf2 candidate region to a 3.0Mb region
between Cntnap3 and Ak029746. This region contains 48 genes and a majority of them
encode zinc finger proteins. The
specific crosses gave unexpected results that interfered with the ability to
study the effect of clf2 genotype on
penetrance of CL/P; the limited data suggested that clf2 does not affect penetrance of CL/P in the Wnt9b null embryos.
However, Cross 2 provided an inverse way to address the role of clf2: to test whether clf2 modifies
the methylation of the IAP transposon at Wnt9b
in the clf1 mutant allele. Using the COBRA technique we studied
the methylation levels of the IAP in Wnt9bclf1/Null
embryos segregating at clf2. The results indicated that clf2 modifies the methylation status of
the IAP.
PUBLICATIONS
AWARDS
Medical Genetics Entrance
Scholarship, September 2008
University Graduate
Fellowship, September 2009
PRESENTATIONS
Exit Seminar, June 2010
GRADUATE STUDIES
Field of Study: Genetics
of Cleft Lip
Courses:
MEDG 515: Developmental
Genetics. Dr. Diana Juriloff
MEDG 520: Advances in Human
Molecular Genetics. Dr. Matthew Lorincz
MEDG 530: Human Genetics. Dr.
Jan Friedman
MEDG 548: Directed Studies in
Medical Genetics. Dr. Diana Juriloff
DENT 561: Directed Studies in
Dental Sciences. Dr. Joy Richman