Testosterone rapidly increases the volume of the medial preoptic nucleus in male Japanese quail

Poster (2005)

In many vertebrate species, testosterone (T) influences the volume and cellular characteristics of a variety steroid-dependent nuclei, including the medial preoptic nucleus (POM) of male Japanese quail ... [more ▼]

In many vertebrate species, testosterone (T) influences the volume and cellular characteristics of a variety steroid-dependent nuclei, including the medial preoptic nucleus (POM) of male Japanese quail. The quail POM is a key nucleus in the control of male sexual behavior and exhibits a sex difference (larger in males than in females). In castrated quail, the POM volume is markedly increased by T but previous studies always assessed this effect after a period of 8-14 days and its specific time-course is unknown. We recently reported that antisense treatments suppressing steroid receptor coactivator-1 expression block T effects on POM volume but when treatment was discontinued, a significant increase of POM size occurred within two days. We therefore asked whether this rapid neuroanatomical change was specifically linked to the SCR-1 modulation or reflected the normal rate of T-induced effects. We collected brains from castrated male quail after 1, 2, 8 and 15 days of T treatment (CX+T) while in untreated castrates (CX) brains were collected after 1 or 15 days. The POM volume defined by Nissl staining increased in a time-dependent fashion in CX+T to reach a 40% increase after 15 days while no change was observed in CX. An increase in the average POM volume was detected on day 1 (13%) and this increase was statistically significant (25%) after only 2 days of exposure to T. No volume change was observed in the steroid-insensitive nucleus rotundus. The activation of male sexual behavior was positively correlated with the increase in POM volume. Because new neurons are not incorporated in the adult avian hypothalamus, these rapid volumetric changes must reflect increases in soma size, neuropile or extracellular space. The mechanisms underlying this unexpectedly rapid neural plasticity are currently under study, focusing in particular on the potential modifications of the steroid sensitive aromatase expressing cells. [less ▲]

Inhibition of steroid receptor coactivator-1 blocks estrogen and androgen action on male sex behavior and associated brain plasticity.

in Journal of Neuroscience (2005), 25(4), 906-13

Studies of eukaryotic gene expression demonstrate the importance of nuclear steroid receptor coactivators in mediating efficient gene transcription. However, little is known about the physiological role ... [more ▼]

Studies of eukaryotic gene expression demonstrate the importance of nuclear steroid receptor coactivators in mediating efficient gene transcription. However, little is known about the physiological role of these coactivators in vivo. In Japanese quail, the steroid receptor coactivator-1 (SRC-1) is broadly expressed in steroid-sensitive brain areas that control the expression of male copulatory behavior, and we investigated the role of this coactivator by antisense technology. Daily intracerebroventricular injections of locked nucleic acid (LNA) antisense (AS) oligonucleotides targeting SRC-1 significantly reduced the expression of androgen- and estrogen-dependent male-typical sexual behaviors compared with control animals that received the vehicle alone or scrambled oligonucleotides. Sexual behavior was restored and even enhanced within 48 h after interruption of LNA injections. Western blot analysis confirmed the decrease of SRC-1 expression in AS animals and suggested an overexpression 48 h after the end of injections. The effects of SRC-1 knock-down on behavior correlated with a reduction in volume of the preoptic medial nucleus (POM) when its borders were defined by Nissl staining or by aromatase immunohistochemistry. The amount of aromatase-immunoreactive material in POM was also reduced in the AS compared with the control group. Previous work on SRC-1 knock-out mice raised questions about the importance of this specific coactivator in the regulation of reproductive behavior and development of sexually dimorphic structures in the CNS. Together, the present findings indicate that SRC-1 modulates steroid-dependent gene transcription and behavior and highlight the rapid time course of steroid-induced brain plasticity in adult quail. [less ▲]

Seasonal plasticity in the song control system - Multiple brain sites of steroid hormone action and the importance of variation in song behavior

in Annals of the New York Academy of Sciences (2004), 1016

Birdsong, in non-tropical species, is generally more common in spring and summer when males sing to attract mates and/or defend territories. Changes in the volumes of song control nuclei, such as HVC and ... [more ▼]

Birdsong, in non-tropical species, is generally more common in spring and summer when males sing to attract mates and/or defend territories. Changes in the volumes of song control nuclei, such as HVC and the robust nucleus of the arcopallium (RA), are observed seasonally. Long photoperiods in spring stimulate the recrudescence of the testes and the release of testosterone. Androgen receptors, and at times estrogen receptors, are present in HVC and RA as are co-factors that facilitate the transcriptional activity of these receptors. Thus testosterone can act directly to induce changes in nucleus volume. However, dissociations have been identified at times among long photoperiods, maximal concentrations of testosterone, large song control nuclei, and high rates of song. One explanation of these dissociations is that song behavior itself can influence neural plasticity in the song system. Testosterone can act via brain-derived neurotrophic factor (BDNF) that is also released in HVC as a result of song activity. Testosterone could enhance song nucleus volume indirectly by acting in the preoptic area, a region regulating sexual behaviors, including song, that connects to the song system through catecholaminergic cells. Seasonal neuroplasticity in the song system involves an interplay among seasonal state, testosterone action, and behavioral activity. [less ▲]

Gene knock down via antisense oligonucleotides to the steroid receptor coactivator SRC-1 modulates testosterone-dependent male sexual behavior and neural gene expression

in Hormones & Behavior (2004), 46

Studies of eukaryotic genome expression demonstrate the importance of steroid receptor coactivators in mediating efficient gene transcription. Little is know about the physiological role of these ... [more ▼]

Studies of eukaryotic genome expression demonstrate the importance of steroid receptor coactivators in mediating efficient gene transcription. Little is know about the physiological role of these coactivators in vivo. We recently showed that the Steroid Receptor Coactivator SRC-1 is densely expressed in steroid-sensitive brain areas in birds and its expression is steroid-dependent and sexually differentiated. We tested the role of SRC-1 in the activation by testosterone of male sexual behavior in quail. Daily injections of LNA antisense oligonucleotides in the third ventricle (AS group) significantly reduced the expression of male copulatory behavior in response to exogenous testosterone compared to control animals (Ctrl group) receiving the vehicle alone or scrambled LNA. Sexual behavior was restored and even enhanced within 48 hours after interruption of LNA injection (ASSC group). Western blot analysis confirmed the decrease of SRC-1 expression in AS animals and suggested an over-expression of the coactivator in ASSC animals. The effect of SRC-1 knock down on behavior was correlated with a reduced volume of the medial preoptic nucleus (POM) defined by Nissl-staining and aromatase immunohistochemistry. In addition, the amount of aromatase-immunoreactive material in POM, defined as the relative optical density of the aromatase immunoreactivity multiplied by the percentage of surface covered within the nucleus and by the total POM volume of the POM, was decreased in the AS compared to the Ctrl group, suggesting a blockade of aromatase transcription. Together, these data indicate that SRC-1 functions as a critical regulatory molecule in the brain that modulates steroid-dependent gene transcription and behavior. [less ▲]

Modulation of steroid activity by transcription coactivators in songbirds

in Hormones & Behavior (2003), 44

Songbirds have developed a specialized, steroid-dependent telencephalic vocal control system for the production of learned vocalization. Recent progress in the study of the mechanisms by which steroid ... [more ▼]

Songbirds have developed a specialized, steroid-dependent telencephalic vocal control system for the production of learned vocalization. Recent progress in the study of the mechanisms by which steroid receptors act on the eukaryotic genome has highlighted the role of a newly discovered protein family, the Nuclear Receptor Coactivators. More specifically, the CREB-binding protein (CBP) and the Steroid Receptor Coactivator-1 (SRC-1) have been shown to be actively involved in mediating steroid hormone action in the developing rat brain. The distribution of the coactivator SRC-1 was analyzed in canaries by in situ hybridization. A very broad but heterogeneous distribution of the transcript was observed, mainly in steroid-sensitive areas of the hypothalamus, the song control system and several catecholaminergic areas. The presence of SRC-1 in these regions was also confirmed by immunocytochemistry. A similar very high concentration of the coactivator CBP protein was also found in steroid-sensitive areas of the hypothalamus and in the song system. Sex differences in SRC-1 mRNA concentration were detected in HVC and in area X. Moreover, preliminary data obtained independently in starlings (CBP) and in quail (SRC-1) suggest that the expression of coactivators is regulated by steroids as well as by photoperiod. The presence of these steroid receptor coactivators in the telencephalic song control nuclei and in catecholaminergic cell groups that innervate the song system and their possible regulation by photoperiod and/or steroids support the idea that SRC-1 and CBP could play an important role in the control of singing behavior by modulating estrogen and androgen receptor action. [less ▲]

Cloning and identification of functional domains in quail Brain aromatase

Poster (2003)

Recent evidence indicates that aromatase activity (AA) in the hypothalamus is not only modulated by slow (hours to days) genomic actions but also through fast (seconds to minutes) non-genomic mechanisms ... [more ▼]

Recent evidence indicates that aromatase activity (AA) in the hypothalamus is not only modulated by slow (hours to days) genomic actions but also through fast (seconds to minutes) non-genomic mechanisms. We recently showed that Calcium (Ca2+)-dependent phosphorylations catalyzed by multiple protein kinases including PKC, and possibly PKA and CAMK, rapidly down-regulate AA in quail hypothalamic homogenates. Western blotting experiments also indicated that phosphorylations affect the aromatase molecule itself but it was impossible to fully characterize the putative phosphorylation sites on the quail enzyme because its sequence was unknown. We therefore cloned and sequenced the quail brain aromatase. We identified a 1541-bp open reading frame that encodes a predicted 490-amino acid protein containing all functional domains previously described in mammalian and other avian aromatases. Multiple motifs match consensus sequences corresponding to several protein kinases including those that were shown to affect AA during pharmacological experiments with specific kinase inhibitors (e.g., PKC, PKA, MAPK, Myosine light chain kinase, Tyr. kinase). Another potential control pathway of AA, independent from phosphorylations, could involve a direct control by Ca2+-dependent calmodulin (CAM), as suggested by the identification in Western blots of CAM on purified aromatase from quail hypothalamic homogenates. Accordingly, two Ca2+-dependent calmodulin binding motifs (1-8-14b) as defined by Rhoads and Friedberg (FASEB, 1997, 11:331-340) are present and conserved in most vertebrates including quail aromatase. These results suggest that the phosphorylation of some residues as well as the direct binding of calmodulin on the aromatase protein represent part of the mechanism(s) underlying the rapid changes in AA. [less ▲]

Sex difference in the distribution of the steroid receptor coactivator SRC-1 in the song control nuclei in male and female canaries

Poster (2002)

Sexually differentiated expression of the steroid receptor coactivator SRC-1 in steroid- sensitive brain areas regulating reproductive behaviors in the quail brain

Poster (2002)

Steroid receptor coactivator SRC-1 exhibits high expression in steroid-sensitive brain areas regulating reproductive behaviors in the quail brain.

in Neuroendocrinology (2002), 76(5), 297-315

The steroid receptor coactivator SRC-1 modulates ligand-dependent transactivation of several nuclear receptors, including the receptors for sex steroid hormones. Reducing the expression of SRC-1 by ... [more ▼]

The steroid receptor coactivator SRC-1 modulates ligand-dependent transactivation of several nuclear receptors, including the receptors for sex steroid hormones. Reducing the expression of SRC-1 by injection of specific antisense oligonucleotides markedly inhibits the effects of estrogens of the sexual differentiation of brain and behavior in rats and inhibits the activation of female sexual behavior in adult female rats. SRC-1 thus appears to be involved in both the development and activation of sexual behavior. In the Japanese quail brain, we amplified by RT-PCR a 3,411-bp fragment extending from the HLH domain to the activating domain-2 of the protein. The quail SRC-1 is closely related to the mammalian (m) SRC-1 and contains a high proportion of GC nucleotides (62.5%). Its amino acid sequence presents 70% identity with mammalian SRC-1 and contains the three conserved LXXLL boxes involved in the interaction with nuclear receptors. In both males and females, RT-PCR demonstrates a similarly high level of expression in the telencephalon, diencephalon, optic lobes, brain stem, spinal cord, pituitary, liver, kidney, adrenal gland, heart, lung, gonads and gonoducts. Males express significantly higher levels of SRC-1 in the preoptic area-hypothalamus than females. In both sexes, lower levels of expression are observed in the cerebellum and muscles. In situ hybridization utilizing a mixture of four digoxigenin-labeled oligonucleotides confirms at the cellular level the widespread distribution of SRC-1 mRNA in the brain and a particularly dense expression in steroid-sensitive areas that play a key role in the control of male sexual behavior. These data confirm the presence and describe for the first time the SRC-1 distribution in the brain of an avian species. They confirm its broad, nearly ubiquitous, distribution in the entire body including the brain as could be expected for a coactivator that regulates to the action of many nuclear receptors. However this distribution is heterogeneous in the brain and sexually differentiated in at least some areas. The very dense expression of SRC-1 in limbic and mesencephalic nuclei that are associated with the control of male sexual behavior is consistent with the notion that this coactivator plays a significant role in the activation of this behavior. [less ▲]

Cloning and distribution of steroid receptor coactivator SRC-1 in quail.

Poster (2001)