RNA interference of gonadotropin-inhibitory hormone gene induces arousal in songbirds.

Gonadotropin-inhibitory hormone (GnIH) was originally identified in quail as a hypothalamic neuropeptide inhibitor of pituitary gonadotropin synthesis and release. However, GnIH neuronal fibers do not only terminate in the median eminence to control anterior pituitary function but also extend widely in the brain, suggesting it has multiple roles in the regulation of behavior. To identify the role of GnIH neurons in the regulation of behavior, we investigated the effect of RNA interference (RNAi) of the GnIH gene on the behavior of white-crowned sparrows, a highly social songbird species. Administration of small interfering RNA against GnIH precursor mRNA into the third ventricle of male and female birds reduced resting time, spontaneous production of complex vocalizations, and stimulated brief agonistic vocalizations. GnIH RNAi further enhanced song production of short duration in male birds when they were challenged by playbacks of novel male songs. These behaviors resembled those of breeding birds during territorial defense. The overall results suggest that GnIH gene silencing induces arousal. In addition, the activities of male and female birds were negatively correlated with GnIH mRNA expression in the paraventricular nucleus. Density of GnIH neuronal fibers in the ventral tegmental area was decreased by GnIH RNAi treatment in female birds, and the number of gonadotropin-releasing hormone neurons that received close appositions of GnIH neuronal fiber terminals was negatively correlated with the activity of male birds. In summary, GnIH may decrease arousal level resulting in the inhibition of specific motivated behavior such as in reproductive contexts

Seasonal Differences of Gene Expression Profiles in Song Sparrow (Melospiza melodia) Hypothalamus in Relation to Territorial Aggression

) are territorial year-round; however, neuroendocrine responses to simulated territorial intrusion (STI) differ between breeding (spring) and non-breeding seasons (autumn). In spring, exposure to STI leads to increases in luteinizing hormone and testosterone, but not in autumn. These observations suggest that there are fundamental differences in the mechanisms driving neuroendocrine responses to STI between seasons. Microarrays, spotted with EST cDNA clones of zebra finch, were used to explore gene expression profiles in the hypothalamus after territorial aggression in two different seasons.Free-living territorial male song sparrows were exposed to either conspecific or heterospecific (control) males in an STI in spring and autumn. Behavioral data were recorded, whole hypothalami were collected, and microarray hybridizations were performed. Quantitative PCR was performed for validation. Our results show 262 cDNAs were differentially expressed between spring and autumn in the control birds. There were 173 cDNAs significantly affected by STI in autumn; however, only 67 were significantly affected by STI in spring. There were 88 cDNAs that showed significant interactions in both season and STI.Results suggest that STI drives differential genomic responses in the hypothalamus in the spring vs. autumn. The number of cDNAs differentially expressed in relation to season was greater than in relation to social interactions, suggesting major underlying seasonal effects in the hypothalamus which may determine the differential response upon social interaction. Functional pathway analyses implicated genes that regulate thyroid hormone action and neuroplasticity as targets of this neuroendocrine regulation

Role of Aryl Hydrocarbon Receptor in Circadian Rhythm: A Novel Pathway to Dioxin Toxicity

114 p.Thesis (Ph.D.)--University of Illinois at Urbana-Champaign, 2006.For decades, the study of aryl hydrocarbon receptor (AhR), a transcription factor and a member of the basic helix-loop-helix/Per-ARNT-Sim (bHLH-PAS) domain family, has been focused on its role in mediating adverse effects of some environmental contaminants, such as 2,3,7,8-tetrachlorodibenzo- p-dioxin (TCDD). However, a physiological role of AhR remains unknown. Many members of PAS domain family play a role in regulation of circadian rhythm; therefore the role of AhR in the circadian rhythm was investigated. First, to examine AhR as a basic component of the molecular clockwork, the circadian mRNA expression of AhR and its signaling targets in the suprachiasmatic nucleus (SCN), the master clock, and in the liver, a peripheral clock, were determined in mice. The circadian phenotype was also characterized in mice lacking AhR. Although not robust as some of the well-characterized clock genes, diurnal variation was observed in both tissues under light/darkness and constant darkness conditions. Second, the role of tryptophan (TRP) photoproducts that act as AhR agonists, were assessed in the light-regulation of circadian rhythm. Both exposure to light or treatment with TRP photoproducts activated AhR signaling in vitro and in vivo. Glutamate-induced phase shifting was inhibited by preincubation with FICZ in in vitro SCN slice cultures. Lastly, potential effects of TCDD on circadian rhythm were examined at the molecular and behavioral level. Exposure to TCDD affected circadian expression of clock genes and attenuated the light-induced phase shifts. Taken together, these results suggest that the AhR is potentially involved in regulating the molecular clockwork, especially in the light-regulatory pathway of circadian rhythm; exposure to environmental contaminants that interact with AhR may affect the ability of humans and animals to adjust their circadian rhythm to the external environment. Although further studies are necessary to decipher mechanisms of how AhR plays a role in circadian rhythm, this work opens new perspectives in both dioxin toxicology and chronobiology.U of I OnlyRestricted to the U of I community idenfinitely during batch ingest of legacy ETD

Role of Aryl Hydrocarbon Receptor in Circadian Rhythm: A Novel Pathway to Dioxin Toxicity

114 p.Thesis (Ph.D.)--University of Illinois at Urbana-Champaign, 2006.For decades, the study of aryl hydrocarbon receptor (AhR), a transcription factor and a member of the basic helix-loop-helix/Per-ARNT-Sim (bHLH-PAS) domain family, has been focused on its role in mediating adverse effects of some environmental contaminants, such as 2,3,7,8-tetrachlorodibenzo- p-dioxin (TCDD). However, a physiological role of AhR remains unknown. Many members of PAS domain family play a role in regulation of circadian rhythm; therefore the role of AhR in the circadian rhythm was investigated. First, to examine AhR as a basic component of the molecular clockwork, the circadian mRNA expression of AhR and its signaling targets in the suprachiasmatic nucleus (SCN), the master clock, and in the liver, a peripheral clock, were determined in mice. The circadian phenotype was also characterized in mice lacking AhR. Although not robust as some of the well-characterized clock genes, diurnal variation was observed in both tissues under light/darkness and constant darkness conditions. Second, the role of tryptophan (TRP) photoproducts that act as AhR agonists, were assessed in the light-regulation of circadian rhythm. Both exposure to light or treatment with TRP photoproducts activated AhR signaling in vitro and in vivo. Glutamate-induced phase shifting was inhibited by preincubation with FICZ in in vitro SCN slice cultures. Lastly, potential effects of TCDD on circadian rhythm were examined at the molecular and behavioral level. Exposure to TCDD affected circadian expression of clock genes and attenuated the light-induced phase shifts. Taken together, these results suggest that the AhR is potentially involved in regulating the molecular clockwork, especially in the light-regulatory pathway of circadian rhythm; exposure to environmental contaminants that interact with AhR may affect the ability of humans and animals to adjust their circadian rhythm to the external environment. Although further studies are necessary to decipher mechanisms of how AhR plays a role in circadian rhythm, this work opens new perspectives in both dioxin toxicology and chronobiology.U of I OnlyRestricted to the U of I community idenfinitely during batch ingest of legacy ETD

Altered prostatic epithelial proliferation and apoptosis, prostatic development, and serum testosterone in mice lacking cyclin-dependent kinase inhibitors

Normal prostatic development and some prostatic diseases involve altered expression of the cell-cycle regulators p27 and p21 (also known as CDKN1B and CDKN1A, respectively). To determine the role of these proteins in the prostate, we examined prostatic phenotype and development in mice lacking p27 and/or p21. In p27-knockout (p27KO) mice, epithelial proliferation was increased 2- and 3.8-fold in the ventral and dorsolateral prostate, respectively, versus wild-type (WT) mice, although prostatic weights were not different. Epithelial apoptosis was increased in p27KO mice and may account for the lack of a concurrent increase in weight. Testosterone deficiency observed in this group was not the cause of this increase, because vehicle- and testosterone-treated p27KO mice had similar percentages of apoptotic cells. Also observed was a trend toward a decreased functional epithelial cytodifferentiation, indicating a potential role of p27 in this process. Conversely, dorsolateral prostate and seminal vesicle (SV) of p21-knockout (p21KO) mice, and all prostatic lobes and SV of p21/p27 double-knockout mice, weighed significantly less compared to the WT mice, and their epithelial proliferation was normal. Decreased testosterone concentrations may contribute to the decreased prostatic weights. However, other factors may be involved, because testosterone replacement only partially restored prostatic weights. We conclude that loss of p27 increases prostatic epithelial proliferation and alters differentiation but does not result in prostatic hyperplasia because of increased epithelial cell loss. The p21 KO mice showed phenotypes distinctly different from those of p27KO mice, suggesting nonredundant roles of p21 and p27 in prostatic development. Loss of p27 or of both p21 and p27 results in serum testosterone deficiency, complicating analysis of the prostatic effects of these cell-cycle regulators