PARENT SESSION
GENE REGULATION AND FUNCTION IN THE REPRODUCTIVE AXIS
Kent
7:30 AM-10:00 AM

(367) CHARACTERIZATION OF TRANSGENIC MICE WITH CONDITIONAL OVER-EXPRESSION OF ESTROGEN RECEPTOR AND RESCUE OF REPRODUCTIVE PHENOTYPE OF ESTROGEN RECEPTOR KNOCKOUT MICE.

Tilli, Maddalena^1,3, Hruska, Kathleen⁴, Frech, Maria Silvina³, Korach, Kenneth⁵, Lubahn, Dennis⁶, Flaws, Jodi², Furth, Priscilla³, ¹ Graduate Program in Human Genetics, Baltimore, MD³ Lombardi Cancer Center, Washington, DC⁴ Gene Evaluation and Mapping Laboratory, Beltsville, MD⁵ Laboratory of Reproductive and Developmental Toxicology, Research Triangle Park, NC⁶ Departments of Biochemistry and Child Health, Columbia, MO² Department of Epidemiology and Preventive Medicine, Baltimore, MD

ABSTRACT- Transgenic and knockout animals allow for the investigation of the consequences of expressing or disrupting genes that play important roles in certain diseases. Conditional transgenics have provided an in vivo method of controlling the spatial and temporal regulation of gene expression. In order to explore the various roles estrogen receptor (ER) may play in reproduction, a mouse model system with conditional regulation of ER was established. Transgenic mice generated previously expressed a construct with the tetracycline transactivator (tTA) under the control of the mouse mammary tumor virus-long terminal repeat (MMTV-LTR) promoter (MMTV-tTA mice) and were used in combination with new tetracycline operator (tet-op)-ER transgenic mice. The MMTV-LTR promoter targets expression of tTA to epithelial cells of secretory organs and skin, thereby conferring tissue specificity. The tTA confers temporal control of ER gene expression by binding to upstream tet-op sequences in the absence of antibiotics such as tetracycline or doxcycyline, a tetracycline analog. Administration of either antibiotic prevents binding of tTA to tet-op sequences, thereby repressing transgene-specific ER expression. Three lines of double transgenic mice were generated. The current study focused on characterization of tissue expression of ER in this conditional transgenic model. The double transgenic mice were taken off doxycycline to allow for expression of ER and tissue samples were collected after various time periods off the antibiotic. Qualitative expression of ER was detected by RT-PCR and non-radioactive Southern blot analysis. Preliminary evidence suggests that both male and female reproductive tissues have been targeted, including the mammary gland. The utility of the dominant gain of ER mouse model was tested by breeding these mice with the ER knockout (ERKO) mice in an attempt to rescue the ERKO reproductive phenotypes. ERKO phenotype rescue was determined by examination of mammary glands and male reproductive tract of mice double transgenic for the MMTV-tTA and tet-op-ER constructs on an ER null background.

KEY WORDS: Estrogen Receptor , Transgenic Mice, Conditional Transgenics, Reproductive Phenotype