CIS-ACTING DNA ELEMENTS INVOLVED IN OOCYTE-SPECIFIC EXPRESSION OF MOUSE SPERM RECEPTOR GENE MZP3 ARE LOCATED CLOSE TO THE GENES TRANSCRIPTION START SITE

We report that cis-acting DNA elements involved in oocyte-specific exp ression of the mouse sperm receptor gene (mZP3) are located close to t he gene's transcription start site. Mice bearing a transgene that cons ists of only 153 nt of mZP3 5'-flanking region fused to the firefly lu ciferase gene (153-ZP3/LUC) expressed the reporter gene in ovary not i n a wide variety of tissues; although two of three lines carrying 153- ZP3/LUC also expressed the transgene in forebrain and hypothalamus. Wi thin the ovaries of transgenic mice, luciferase activity was restricte d to growing oocytes. However, levels of luciferase activity in these oocytes were lower than those in oocytes from mice bearing transgenes that contain a larger segment of mZP3 5'-flanking region (470-6,500 nt ) fused to the firefly luciferase gene. Mice bearing a transgene that consists of 470 nt of mZP3 5'-flanking region and mZP3 intragenic sequ ences (ZDT) were also analyzed. The presence of mZP3 intragenic sequen ces did not result in significantly increased levels of firefly lucife rase activity in oocytes of mice carrying the ZDT transgene. Overall, these results suggest that as little as 153 nt of mZP3 5'-flanking reg ion is sufficient to target expression of the firefly luciferase gene to mouse oocytes and that the mZP3 intragenic sequences probably do no t contain enhancer elements. Rather, enhancer elements are probably pr esent between -153 and -470 nt of the mZP3 5'-flanking region. (C) 199 3 Wiley-Liss, Inc.