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Research Project
My current research involves exploring the changes in global
gene expression patterns in the livers of immature ovariectomized
C57BL/6 mice treated with ethynyl estradiol (EE), a synthetic
estrogen. Mice were gavaged once or 3x24hr with 0.1mg/kg EE
or vehicle and livers were harvested at 0, 2, 4, 8, 12, 24 or
72 hrs. cDNA microarrays are used to assess relative expression
levels of transcripts isolated from treated and control populations
of animals. Samples from EE treated mice are co-hybridized with
samples from time-matched vehicle controls (TMV). To identify
genes with significant expression changes, least squares means
from a general linear mixed model of EE samples were compared
to TMV samples using t-tests. Approximately 4-8% of the genes
examined at each time point exhibited significant changes in
expression (p<0.01). A large number of second messenger,
transcription factor and signal transduction genes and various
cytochrome P-450 enzymes involved in steroid and cholesterol
biosynthesis were identified that were significantly altered
in response to EE. The promoters of many of these genes were
retrieved from the UCSC database, screened for the presence
of perfect estrogen response elements (EREs) and were found
to contain this motif suggesting direct regulation by estrogen.
The dramatic alteration of diverse signaling cascades illustrates
the complexity of estrogen action in the liver. This, combined
with the importance of the liver in metabolism and toxicity,
suggests that evaluating hepatic responses will be important
in future assessments of estrogen action in the intact organism.
My other area of interest involves investigating the effects
of TCDD on immunosuppression in B-cells. The B-cell, a major
component of humoral immunity, is a sensitive target for the
immunotoxic effects of 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD)
possibly by rendering B-cells less responsive to antigen or
mitogen stimulation. The potential mechanisms of TCDD action
on B-cells were examined in murine B-cell lymphoma cells (CH12LX)
treated with 3 nM TCDD or DMSO vehicle for 0, 2, 4, 6, 8, 12
and 24 hrs using a sequence verified cDNA microarray representing
3068 genes/ESTs. Quantitative real-time PCR was used to verify
the microarray results and statistical significance was determined
using the t-test (p<0.05). Cyp1a1 and Cyp1a2 displayed characteristic
induction profiles with maximum induction of 300- and 6-fold,
respectively, at 4 hrs. We hope to identify other genes which
are induced/repressed in response to TCDD in B-cells that may
help to explain the immunosuppressant effects of TCDD.
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