Identification of molecular circuits involved in epigenetic re-modelling in the ovine pars tuberalis using next generation sequencing data

Seasonally breeding mammals use photoperiod as a critical cue to drive hormone rhythms and synchronize reproduction to the optimal time of year. Photoperiod is encoded by the nocturnal secretion of melatonin (MEL). MEL acts on the pars tuberalis (PT) of the pituitary, regulating PT-specific expression of thyrotropin, controlling hypothalamic thyroid hormone metabolism in adjacent ependymal cells, which drives reproductive changes.
We employed Next Generation Sequencing(NGS) data to define the full repertoire of transcriptional changes within the PT following exposure to long photoperiod(LP). Sheep were housed for 12 weeks on a short photoperiod(SP) and cohorts were exposed to LP for 1, 7 or 28 days. RNASeq reads using the Illumina platform were mapped to the sheep genome. The number of reads mapping to each gene was calculated and normalised to the total number of reads generated. Using edgeR a statistical analysis was performed to identify genes differentially expressed at LP compared to SP. Further to this, an analysis using Biolayout was performed, this takes into account small changes in expression and identifies genes exhibiting similar patterns of expression, for subsequent cluster analysis. The goal is to examine the data as a whole and identify groups of genes that are co-expressed, and may have similar functions.
Our results suggest there may be dramatic tissue/vasculature remodelling of the PT in response to photoperiod. Furthermore, we hypothesise that the observed epigenetic changes may play a role in these seasonal tissue re-modelling responses. To sum up, using bioinformatics analysis based on NGS data we have identified dynamic changes of circuits involved in epigenetic changes, and possible tissue/vasculature remodelling of the PT in response to photoperiod.