THE TISSUE-SPECIFICITY OF MOUSE Ets-1 REGULATORY REGION IN A TRANSGENIC MODEL

Abstract

Cellular differentiation is the result of the selective expression of gene products that determine cellular phenotype. To identify the cis - acting control elements of developmentally-regulated genes, it is necessary to be able to identify genetic regions that direct tissue- specific expression in a developmental system. Transgenic analysis involves the introduction of cloned genes into mice by pronuclear injection of fertilized eggs. This method allows for a comprehensive analysis of the temporal and tissue-specific expression of a developmentally-regulated gene. Recently, Ets-1, a developmentally-regulated protooncogene, was determined by in situ analysis to be expressed in various tissues during mouse development and at high levels in the lymphoid and vascular structures. The Ets-1 gene product is a DNA-binding protein that may function in the regulation of many genes through interactions with specific nucleotide sequences in gene promoters. To better understand the regulation of Ets-1, further analysis is required to identify tissue-specificity and control regions that regulate expression. In this thesis, 2.4 kb of the 5' flanking region of the Ets-1 promoter was fused to the lacZ gene and microinjected into mouse pronuclei. Transgenic mice expressed the Ets-1/lacZ fusion gene aberrantly in the central nervous system. No detectable lymphoid or vascular expression was observed. However, certain transgenic expression showed positive correlation with the in situ analysis. These results indicate that the "functional" promoter of Ets-1 previously described by several labs (Jorcyk et al., 1991, and Marjeus et al., 1992) is not sufficient to facilitate tissue-specific expression. Therefore, lymphoid and vascular-specific enhancers must still be identified in the molecular organization of Ets-1. Furthermore, negative regulatory elements may be present in Ets-1 that suppress neuronal expression.