Protooncogene c-fos Involvement in the Molecular Mechanism of Rat Brain Sexual Differentiation.
Brain sexual differentiation is mediated through testosterone, which acts during the perinatal period in the form of both 5alpha-dihydrotestosterone and estradiol. In order to gain insight into the molecular mechanisms involved, we studied induction of c-fos, an index of functional neuronal activation, in the 2-day-old female rat brain after injection of a masculinizing dose of testosterone. Administration of testosterone resulted in induction of c-fos gene expression in the hypothalamus, as determined by Northern analysis. Following immunocytochemistry, we demonstrated an increase in the number of Fos-positive nuclei in the median and medial preoptic nucleus, the medial preoptic area extending to the lateral preoptic area, and the peri- and paraventricular area. In an effort to see whether testosterone acted as 5alpha-dihydrotestosterone or as estradiol, we injected either steroid and looked at fos induction. Estradiol mimicked the effect of testosterone, while 5alpha-dihydrotestosterone was without effect. Furthermore, injection of an estrogen receptor blocker, clomiphene, together with testosterone, abolished the testosterone-induced increase in Fos-positive nuclei, thus confirming the finding that testosterone induces c-fos by acting through estrogen receptors. Electrophoretic mobility shift assays showed that nuclear extracts from 2-day-old female hypothalamus contain a protein, most probably the estrogen receptor, which binds specifically to oligodeoxynucleotides with the sequence of either vitERE, the consensus estrogen-responsive element (ERE) found in the vittelogenin gene, or fosERE, the ERE found in the 3'-untranslated region of the mouse c-fos gene. This suggests that the effect of testosterone-derived estradiol on c-fos expression is a direct one, mediated by binding of estrogen receptors to an ERE in the c-fos gene-regulatory regions.
Giannakopoulou
M
M
Laboratory of Biology-Biochemistry, Faculty of Nursing, University of Athens, Greece.
Bozas
E
E
Philippidis
H
H
Stylianopoulou
F
F
D000818:Animals; D000831:Animals, Newborn; D015152:Blotting, Northern; D001921:Brain / Q000187:drug effects / Q000254:growth & development* / Q000378:metabolism; D002996:Clomiphene / Q000494:pharmacology; D013196:Dihydrotestosterone / Q000494:pharmacology; D004958:Estradiol / Q000494:pharmacology; D005260:Female; D015870:Gene Expression / Q000187:drug effects; D007031:Hypothalamus / Q000737:chemistry / Q000378:metabolism; D007150:Immunohistochemistry; D016760:Proto-Oncogene Proteins c-fos / Q000032:analysis / Q000235:genetics / Q000502:physiology*; D051381:Rats; D017208:Rats, Wistar; D011960:Receptors, Estrogen / Q000037:antagonists & inhibitors; D012727:Sex Characteristics; D013739:Testosterone / Q000008:administration & dosage / Q000494:pharmacology
D016760:Proto-Oncogene Proteins c-fos; D011960:Receptors, Estrogen; D013196:Dihydrotestosterone; D002996:Clomiphene; D013739:Testosterone; D004958:Estradiol