Transcriptome profiling of the ovine pars tuberalis in long and short photoperiod conditions

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. Overall design: Short photoperiod (SP) - 5 samples, Long photoperiod (LP) day 1 - 6 samples, LP day 7 - 6 samples, LP day 28 - 6 samples

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Wood SH, Christian HC, Miedzinska K, Saer BR, Johnson M, Paton B, Yu L, McNeilly J, Davis JR, McNeilly AS, Burt DW, Loudon AS