Protooncogene c-fos Involvement in the Molecular Mechanism of Rat Brain Sexual Differentiation

Abstract

Brain sexual differentiation is mediated through testosterone, which acts during the perinatal period in the form of both 5α-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 5α-dihydrotestosterone or as estradiol, we injected either steroid and looked at fos induction. Estradiol mimicked the effect of testosterone, while 5α-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.

Sex differences in drug addiction and response to exercise intervention: From human to animal studies

“…Moreover, a very recent study revealed that acute administration with methamphetamine caused a greater activation of c-Fos receptor-positive cells in male mice than females in the hippocampus (Zuloaga et al , 2014). Gonadal hormones may be a major factor in these disparities, given that testosterone and estradiol induce Fos gene expression in adult and developmental rat brains, which are mediated by the binding of estrogen receptors (Giannakopoulou et al , 2001; Olesen and Auger, 2005). In addition, some studies have found that exercise-induced estrogen increases in OVX rats contributed to the improvement of emotional and cognitive disorders, which were induced by the lack of estrogen (Ben et al , 2010; Lu et al , 2014).…”

Neonatal handling on the first postnatal day leads to increased maternal behavior and fos levels in the brain of the newborn rat

“…More particularly, in the developing rat brain c-fos induction has been used to study the ontogeny of the fear response (Wiedenmayer & Barr, 2001), the functional maturation of the amygdala (Moriceau, Roth, Okotoghaide, & Sullivan, 2004), the maturation of the circadian photicresponse in the suprachiasmatic nucleus (Leard, Macdonald, Heller, & Kilduff, 1994), the development of the stress response (Dent, Smith, & Levine, 2001;Levine, 2002), the ontogeny of the oxygen-sensitive pathway in the medulla oblongata (White, Lawson, & Millhorn, 1994) and the response to neurotoxic insults such as anoxia (Tang, Ringstedt, Pequignot, & Lagercrantz, 2000), hypoxia (Ringstedt, Tang, Persson, Lendahl, & Lagercrantz, 1995), ischemia (Pabello, Tracy, SnyderKeller, & Keller, 2005), exposure to alcohol or cocaine (Mitchell & Snyder-Keller, 2003). Furthermore, c-fos expression has been employed to map brain areas activated during nursing (Hironaka, Shirakawa, Toki, Kinoshita, & Oguchi, 2000) and in the process of sexual differentiation of the brain (Giannakopoulou, Bozas, Philippidis, & Stylianopoulou, 2001;Olesen & Auger, 2005).…”

Progesterone receptor gene and protein expression in the anterior preoptic area and hypothalamus of defeminized rats

“…2). This observation suggests that both estradiol and testosterone administration during the postnatal critical period modifies the normal expression of estrogen-regulated genes involved in sexual differentiation of POA and HYP (Arrieta et al, 2000;Giannakopoulou et al, 2001).…”