Project description:Annual cycles in daylength provide an initial predictive environmental cue that plants and animals use to time seasonal biology. Seasonal changes in photoperiodic information acts to entrain endogenous programs in physiology to optimize an animal’s fitness. Attempts to identify the neural and molecular substrates of photoperiodic time measurement in birds have, to date, focussed on blunt changes in light exposure during a restricted period of photoinducibility. The objectives of these studies were first to characterise a molecular seasonal clock in Japanese quail and second, to identify the key transcripts involved in endogenously generated interval timing that underlies photosensitivity in birds. We hypothesized that the mediobasal hypothalamus (MBH) provides the neuroendocrine control of photoperiod-induced changes in reproductive physiology, and that the pars distalis of the pituitary gland contains an endogenous internal timer for the short photoperiod dependent development of reproductive photosensitivity. Here we report distinct seasonal waveforms of transcript expression in the MBH, and pituitary gland and discovered the patterns were not synchronized across tissues. Follicle-stimulating hormone-β (FSHβ) expression increased during the simulated spring equinox, prior to photoinduced increases in prolactin, thyrotropin-stimulating hormone-β and testicular growth. Diurnal analyses of transcript expression showed sustained elevated levels of FSHβ under conditions of the spring equinox, compared to autumnal equinox, short (<12L) and long (>12L) photoperiods. FSHβ expression increased in quail held in non-stimulatory short photoperiod, indicative of the initiation of an endogenously programmed interval timer. These data identify that FSHβ establishes a state of photosensitivity for the external coincidence timing of seasonal physiology. The independent regulation of FSHβ expression provides an alternative pathway through which other supplementary environmental cues, such as temperature, can fine tune seasonal reproductive maturation and involution.

Project description:Purpose: Photoperiod is known to cause physiological changes in seasonal mammals, including body weight, physical activity, and reproductive status. Because cats are seasonal breeders, we recently tested the effects of day length on resting metabolic rate, voluntary physical activity, and food intake. In that study, resting metabolic rate, physical activity, and food intake to maintain body weight were greater in cats exposed to long days vs. short days. Because photoperiod has also been demonstrated to affect adipose tissue gene expression in several species, including dairy cows, sheep, and Siberian hamsters, the objective of this study was to determine the effects of day length on the adipose transcriptome profile of cats as assessed by RNA-seq. Methods: Ten healthy adult neutered male domestic shorthair cats were used in a randomized crossover design study. During two 12-wk periods, cats were exposed to either short days (8 hr light:16 hr dark) or long days (16 hr light:8 hr dark). Cats were fed a commercial diet to maintain baseline body weight. Subcutaneous adipose biopsies were collected at wk 12 of each period for RNA isolation and Illumina sequencing. Results: A total of 578 million sequences (28.9 million/sample) were generated by Illumina sequencing. Using a raw p value of P<0.005, 170 mRNA transcripts were differentially expressed between short day- and long day-housed cats. Of the 170 transcripts highlighted, 25 annotated transcripts were up-regulated, while 116 annotated transcripts were down-regulated by long days. Another 29 un-annotated transcripts (name and function not known) were also different between groups. In general, adipose tissue of long day-housed cats had greater expression of genes involved with cholesterol trafficking, fatty acid synthesis and immune function, and lower expression of genes involved with cell cycle and growth, cell development and structure, and protein processing, when compared to short day-housed cats. Subcutaneous adipose tissue mRNA profiles of healthy adult neutered male cats exposed to short days (8 hr light: 16 hr dark) or long days (16 hr light: 8 hr dark) using Illumina sequencing.

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Comparative transcriptomics across photoperiod in the Siberian hamster and Japanese quail brains

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