Altered gene expression related to fuel use and sensory capacity in tanycytes throughout the hibernation season in the golden hamster

Hibernation is a physiological and behavioural adaptation that permits survival during periods of reduced food availability and extreme environmental temperatures. This is achieved through episodes of metabolic depression and body cooling (torpor), and subsequent rewarming (arousal), cycling between these states is presumed to stem from changes in hypothalamic metabolic control. Several recent lines of evidence implicate the hypothalamic tanycytes in this phenomenon. To investigate tanycytic changes over the hibernation season, golden hamsters ( Mesocricetus auratus (Waterhouse, 1839)) were transferred from long photoperiod 22 °C to short photoperiod (SP) 8 °C, sampling animals at physiologically defined points across the hibernation season for LASER capture microdissection, and RNAseq of the tanycytic region. Our analysis revealed a marked reduction in the expression of genes linked to ciliary assembly and G-protein coupled receptor-signalling during the hibernation season, as well as evidence for a shift towards increased glycolytic metabolism. These aspects were all reversed in refractory animals, which spontaneously ceased to express torpor after extended exposure to SP 8 °C. Tanycytes sampled mid-torpor show increased expression of immediate-early genes compared to the interbout euthermic state, while genes linked to RNA processing and translation show the reverse effect. The implications of these findings for the putative involvement of tanycytes in hibernation control mechanisms are discussed.