The circadian (24-h timing) system has the essential task of anticipating daily recurring changes in the environment and adapting our physiology to them. In mammals, the central pacemaker in the hypothalamic suprachiasmatic nucleus (SCN), perceives environmental light and fine-tunes the daily synchronisation of the whole neuroendocrine system and, by that, daily activity, sleep, metabolism, stress responses, among others. The SCN develops during the perinatal period under the influence of signals that convey maternal perception of time, and prepare the newborn for the interaction with the environment after birth (Astiz and Oster, Front Neurosci., 2020). New evidence from our lab challenged the current view on the fetal clock - largely considered immature and non-functional during gestation - suggesting that it controls the diurnal sensitivity to maternal signals (such as glucocorticoids) and determines how the neuroendocrine system is programmed and thus, offspring’s physiology later in life (Astiz et al., Nat. Commun, 2020; Demarez et al., Development, 2021). The aim of our lab is to answer a long-standing question, when and how does the central pacemaker in the SCN start ticking (Astiz et al., Glia, 2021). With a combination of in vivo and in vitro approaches, we will understand which cells, signals and mechanisms are involved in the gradual development of this remarkable brain region. Our ultimate goal is to translate the experimental findings into the clinical setting, mainly in the context of premature birth.

Left: Mouse brain showing the hierarchical organization of the circadian system with the hypothalamic suprachiasmatic nucleus (SCN) as the central pacemaker entrained by environmental light through the retinohypothalamic tract (RHT). The information is sent via multiple neuronal and hormonal pathways to other clocks in the brain and peripheral organs so physiology and behavior are synchronized. Right: SCN location and cellular organization in a coronal brain slice. The SCN is located in the anterior hypothalamus on each side of the third ventricle (3V), above the optic chiasma (OC). Arginine vasopressin (AVP)-expressing neurons populate the dorsal area (shell) and Vasoactive intestinal peptide (VIP)-expressing neurons mainly locate to the ventral area (core). Astrocytes, with a cellular abundance of one third that of the neurons, and oligodendrocytes constitute an integral part of the SCN. Image created by Sylvia A. Newbold with Inkscape.