Hypothalamic tanycytes as mediators of maternally programmed seasonal plasticity

Environments with seasonal fluctuations requires inhabitants to anticipate their metabolic demands to survive. Drastic changes in food availability and temperature impose pressing challenges, especially during the first weeks of life. Offspring born early and late in the breeding season require different metabolic strategies. The mother’s melatonin levels ensures this in utero, acting as an internal mirror of day length. The melatonin levels programs the offspring to either grow fast and reproduce quickly (early born), or grow slow and delay maturation until next spring (late born). Thyroid hormone availability is altered by the melatonin signal and drives these differing metabolic strategies. Tanycytes located in the ependymal zone of the 3rd ventricle of the hypothalamus are at the crux of this change in thyroid hormone availability. Current literature provide ample evidence that these cells serve as a gatekeeper of metabolic feedback circuits, and photoperiodic history cues. Despite recent advances, our mechanistic understanding of how tanycytes regulate metabolic trajectories remains elusive. Here we used a well-established maternal photoperiodic programming paradigm to decipher the mechanism tanycytes utilise to dictate the offspring metabolic trajectory. The paradigm only rely on variable gestational light exposure to alter metabolic phenotype. Laser capture microdissection of ependymal zone enabled us to perform RNAseq on tanycyte enriched samples. Siberian hamsters were gestated either on long photoperiod (LP, 16 hours of light per 24 hours) or short photoperiod (SP, 8 hours of light per 24 hour) and were maintained on those photoperiods until weaning (P21). At weaning (P21), a subgroup of the animals from both LP and SP were assigned to the same intermediate photoperiod (LPIP, SPIP, 14 hours of light per 24 hours). Animals were sampled for laser capture microdissection (LCMD) at P50.