In vivo function of the 5′ flanking region of mouse estrogen receptor β gene

The estrogen receptor (ER) subtypes α and β differentially distributed in tissues, and ERβ is present preferentially in epididymis, testis, prostate, ovary and lung. Although transcription promoter activity has been found in the 5′ flanking (5′f) region of the ERβ gene, it is not known whether the proximal 5′f region is responsible for the tissue-specific distribution. In the present study, we examined the in vivo promoter activity of this region in transgenic mice with the lacZ reporter. About 2.2 kbp of the proximal 5′f region of ERβ was cloned and inserted into reporter plasmids. This 5′f region of mouse ERβ, which displayed a substantial promoter activity in vitro, was very similar to that in rats, but showed limited homology with the human gene. Three independent lines of mice containing ERβ-5′f-lacZ were obtained. Quantitative measurement of mRNA showed that lacZ was expressed only in the testis, in which sertoli cells as well as a part of the spermatogonia were confirmed to be lacZ-positive, in accordance with the known localization of ERβ expression in the testis. The present study suggests that a 2.2 kbp of the 5′f region of the ERβ gene is able to direct testis-specific expression, but is not itself sufficient to determine the expression in other organs.