THE PROXIMAL 350 BP OF 5'-FLANKING SEQUENCE OF THE HUMAN ALPHA-SUBUNIT GLYCOPROTEIN HORMONE GENE FUNCTIONS IN THE PITUITARY-GLAND, BUT NOT THE PLACENTA, IN TRANSGENIC MICE

To understand better the minimal DNA sequence requirements for regulat ed expression of the human alpha-subunit glycoprotein hormone gene (H alpha), two lines of transgenic mice were constructed that contained a fusion gene (H alpha-350CAT) consisting of only 350 bp of 5'-flanking sequence of H alpha linked to the bacterial gene encoding chloramphen icol acetyltransferase (CAT). CAT activity was detectable in pituitary , but not in brain, heart, kidney, liver, lung, pancreas, or spleen in transgenic mice. Gonadectomy increased (p < 0.05) CAT activity in the pituitaries of males (6.5 +/- 1.4% conversion/mu g protein; mean +/- SEM) and females (14.5 +/- 4.2) compared to intact males (1.2 +/- 0.3) and females (6.7 +/- 1.0). In addition, administration of a GnRH anta gonist (antide; 60 mu g/injection; one injection every other day) for 10 d to gonadectomized animals decreased (p < 0.05) CAT activity in ma les (3.5 +/- 0.8) and females (2.9 +/- 0.5) compared to gonadectomized animals that received saline. Antide also reduced (p < 0.05) serum co ncentrations of luteinizing hormone in gonadectomized males and female s compared to gonadectomized animals that received saline. Surprisingl y, CAT activity in the placenta of H alpha-350CAT transgenic mice was not detectable (<3 SD above the mean of CAT activity in placenta from nontransgenic mice; n = 77). Thus, expression of the human alpha-subun it promoter in the placenta of transgenic mice appears to require DNA sequences upstream of the proximal 350 bp of 5'-flanking sequence, whe reas the proximal 350 bp of the human alpha-subunit gene contains suff icient DNA sequence to target pituitary-specific expression and confer responsiveness to gonadal hormones and GnRH.