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Title: CONDITIONAL GENE EXPRESSION IN SECRETORY TISSUES AND SKIN OF TRANSGENIC MICE USING THE MMTV-LTR AND THE TETRACYCLINE RESPONSIVE SYSTEM.

Author
item HENNIGHAUSEN, LOHAR - NIH
item WALL, ROBERT
item TILLMANN, ULRICH - ALTRA BIO INC
item LI, MINGLIN - U OF MD MEDICAL SCHOOL
item FURTH, PRISCILLA - U OF MD MEDICAL SCHOOL

Submitted to: Journal of Cellular Biochemistry
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 5/31/1995
Publication Date: N/A
Citation: N/A

Interpretive Summary: Transgenic animal technology provides the most powerful tool available to study gene regulation. However as currently practiced, the system does have one major limitation. It is not possible to ask some fundamental questions about the role of gene regulation during development. It has also inhibited our ability to enhance grwoth in livestock. If a means were available to turn the newly introduced gene on and off, that constraint would be eliminated. We have recently developed such a system. The system is based on introduction of two gene constructs, one that directs gene expression to the tissue(s) of choice and the other that is responsive to exogenously administered tetracycline. In this report we extended our previous finding by testing our "switch" in secretory tissues and skin. We targeted epithelial cells in seminal vesicles, salivary gland, Leydig cells, mammary gland and skin. Six lines of transgenic mice were generated and tested. When tetracycline was included in drinking water th "switch" was turned off in five of six lines of mice. In the sixth line the "switch" was not completely turned off. When tetracycline was removed from drinking water the "switch" turned on and expression of our reporter gene (luciferase-a light emitting gene) was increased several hundred-fold. These results confirm that we will be able to turn new genes on and off as needed to perform basic research studies and enhance production traits in livestock.

Technical Abstract: Molecular mechanisms of development and disease can be studied in transgenic animals. Controlling the spatial and temporal expression patterns of transgenes, however, is a prerequisite for the elucidation of gene function in the whole organism. Previously we reported that mice carrying a tetR/VP16 hybrid gene (tTA), under the control of the human cytomegalovirus immediate early 1 (HCMV-IE1) gene promoter, can be used to temporally activate the expression of transgenes under the control of a promoter containing tetop sequences. We now show that the MMTV-LTR can be used to target expression of tTA to the epithelial cells of secretory organs and skin in trans- genic mice. Notably, nearly uniform expression of a tetop-lacZ transgene was found in seminal vesicle, salivary gland and Leydig cells of mice carrying also the MMTV-tTA lines trans- gene. More heterogeneous patterns of gene expression were observed in mammary epithelial cells and basal cells of the epidermis. Different MMTV-tTA lines had comparable tissue expression patterns. Transcriptional activation mediated by tTA was up to several hundred-fold, and it was abrogated after the administration of tetracycline. The The MMTV-tTA mice established in this work will be useful for experiments examining the roles of biological factors at defined developmental stages in the epithelial cells of salivary gland, seminal vesicle, mammary gland and skin, and the Leydig cells to testes. In addition, in combination with the CARE/lox recominations systems, these mice will be useful to achieve gene deletions at defined timepoints in these organs.