Different 5'-flanking regions of the inhibin-alpha gene target transgenes to the gonad and adrenal in an age-dependent manner in transgenic mice.
The inhibin-alpha gene is expressed in a tissue-specific manner, and its protein product dimerizes with one of two beta-subunits to form bioactive heterodimers. To characterize the cis-acting elements involved in directing gonad- and adrenal-specific expression of inhibin-alpha, transgenic mice were generated that carried 2.5 or 6 kilobases (kb) of the 5'-flanking region of the mouse inhibin-alpha gene driving the human bcl-2 complementary DNA. Using an antibody specific for human Bcl-2, Western blotting and immunocytochemical analyses showed that both enhancer/promoter fragments direct transgene expression to the ovary, testis, and adrenal gland. The 6-kb fragment targeted the ovarian transgene expression in interstitial cells and young corpora lutea as well as granulosa and thecal cells of secondary, antral, and preovulatory follicles. In ovaries of animals with the 2.5-kb fragment, transgene expression was also detected in interstitial cells and young corpora lutea, but only in granulosa and thecal cells from antral and preovulatory follicles. The ovarian transgene expression in animals carrying the 6-kb inhibin-alpha promoter/bcl-2 construct was stimulated by gonadotropin treatment, with greater than 10-fold increases observed 2 days after PMSG stimulation. In the testes of both types of transgenic animals, immunoreactive Bcl-2 was predominantly detected in Sertoli cells of seminiferous tubules. Sporadic expression was also observed in some interstitial cells. In the adrenal gland, reporter protein was detected in the zona fasciculata of both types of transgenic animals during adult life; however, transgene expression was detected in zona fasciculata of young (21-day-old) animals with the 6-kb, but not the 2.5-kb, promoter construct. Thus, the 2.5-kb inhibin-alpha 5'-proximal DNA sequence directs transgene expression in mature ovarian follicles and testicular Sertoli cells. In contrast, enhancer elements in the 6-kb fragment are required for expression in preantral follicles and in the adrenal of immature animals. The inhibin-alpha promoter/enhancer used here represents unique DNA sequences for ovarian-specific transgene expression and is useful for future analysis of gonadal and adrenal cell functions.
Hsu
S Y
SY
Department of Gynecology and Obstetrics, Stanford University School of Medicine, California 94305-5317, USA.
Lai
R J
RJ
Nanuel
D
D
Hsueh
A J
AJ
D000311:Adrenal Glands / Q000378:metabolism*; D000367:Age Factors; D000818:Animals; D006063:Chorionic Gonadotropin / Q000494:pharmacology; D005260:Female; D018390:Gene Targeting; D006064:Gonadotropins, Equine / Q000494:pharmacology; D006066:Gonads / Q000378:metabolism*; D006801:Humans; D007265:Inhibins / Q000235:genetics*; D008297:Male; D051379:Mice; D008822:Mice, Transgenic; D009928:Organ Specificity; D011401:Promoter Regions, Genetic; D019076:Transgenes
D006063:Chorionic Gonadotropin; D006064:Gonadotropins, Equine; D007265:Inhibins