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Transcriptome profiling of the ovine pars tuberalis in long and short photoperiod conditions [4-22 weeks]

ABSTRACT: Persistent free-running circannual (circa 1-year) rhythms have evolved in animals to regulate hormone cycles and time annual reproduction. In mammals, these are synchronized by environmental photoperiod and the melatonin signal. Long summer-like photoperiods (LP) activates thyrotrophs and thyroid-stimulating hormone (TSH) expression in the melatonin target tissue, the pars tuberalis (PT) region of the pituitary gland, driven by the transcriptional co-activator EYA3. TSH in turn stimulates thyroid hormone (TH) conversion in hypothalamic ependymal tanycytes, thus timing breeding seasons. In contrast to our new knowledge defining photoperiodic input, it is still not known which cells, tissues and pathways generate the underlying circannual cycle. We used seasonal sheep to characterise the circannual cycle, transferring animals from short winter-like photoperiods (SP) to prolonged LP conditions, and assaying prolactin to track circannual phase in individual animals. Using RNA-seq, we profiled PT cells at different phases of the circannual cycle, and defined extensive changes of cellular-remodeling pathways and genes encoding synaptic guidance proteins in the PT.

ORGANISM(S): Ovis aries

PROVIDER: GSE65900 | GEO | 2015/10/09

SECONDARY ACCESSION(S): PRJNA275351

REPOSITORIES: GEO

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Project description:Graves’ disease is characterized by goiter, palpitation and exophthalmos (Merseburg’s trias). However, a few patients develop exophthalmos even though their thyroid function is normal, a condition known as euthyroid Graves’ disease (EGD). It remains unknown why these patients remain euthyroid, even though they have potent thyroid-stimulating antibody (TSAb). To investigate whether the immunoglobulins (IgGs) obtained from EGD patients elicit thyroid hormone-releasing activity (THRA), thyroid follicles obtained from Graves’ patients were cultured in agarose-coated culture dishes, and 125I incorporated into the thyroid follicles and organic 125I (mainly de novo-synthesized 125I-T3+125I-T4) released into the culture medium by TSH or purified IgGs were determined as thyroid hormone-releasing activity (THRA). This thyroid follicle culture system allows maintenance of the Wolff-Chaikoff effect, and the expression of mRNA for the sodium-iodide symporter is decreased by high concentrations of iodide (10-6-10-4M) and therapeutic concentrations of amiodarone (1-2microM). hTSH elicited THRA most efficiently at 0.4-10 microU/ml, suggesting that thyroid function is controlled within the normal range of TSH concentration (0.4-4.0 microU/ml). All IgGs obtained from hyperthyroid Graves’ patients elicited THRA equivalent to more than 4.6 microU/ml hTSH. IgGs obtained from EGD patients also had potent THRA, whereas IgGs obtained from normal subjects and Graves’ patients in complete remission had no significant THRA. When thyroid follicles from Graves’ thyroid, into which a number of lymphocytes had infiltrated, were used, only slight THRA was elicited by bTSH or Graves’ IgGs, probably due to inflammatory cytokines produced by immunocompetent cells that could not be separated during gentle centrifugation. Indeed, when thyroid follicles were cultured with autologous intrathyroidal lymphocytes, interleukin-2 completely abolished TSH-induced THRA. When thyroid follicles were cultured with inflammatory cytokines (interleukin-1, tumor-necrosis factor-alpha, or interferon-gamma), each cytokine inhibited TSH-induced THRA in a concentration-dependent manner. These cytokines at lower concentrations synergistically and completely inhibited TSH-induced THRA. Microarray analyses of thyroid follicles cultured with IL-1alpha, TNF-alpha, or INF-gamma revealed decreased expression of mRNAs for TSHR, NIS, TPO and thyroglobulin, accompanied by increased expression of mRNAs for chemokines and cytokines. These findings suggest that IgGs obtained from patients with EGD have potent THRA in vitro, whereas in vivo, these IgGs are unable to elicit biological activity in the thyroid gland. Presumably, immunocompetent cells that infiltrate the thyroid gland produce inflammatory cytokines that synergistically inhibit thyroid function. Since a similar phenomenon may occur in the retroorbital tissues, these patients may develop exophthalmos despite having a normal serum level of TSH. This data will be published in Hyperthyroidism: Etiology, Diagnosis and Treatment (editor-in-chief;Dr.Frank Clumbus,Nova Science Publishers, Inc, New York, USA) Experiment Overall Design: One conditioned experiments: control vs. IL-1 alpha 5ng/ml, cultured for 24 hours; control vs. TNF alpha 20ng/ml, cultured for 24 hours; control vs. IFN gamma 1000U/ml, cultured for 48 hours.

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Transcriptome profiling of the ovine pars tuberalis in long and short photoperiod conditions [4-22 weeks]

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