By Abdulla Ahmed, Neuroscience
Advisor: Kevin Zhang
Abstract: Thermoregulation is the process of defending core body temperature against varying environmental climates and is essential to all homeotherms. This process is mediated by the central and peripheral nervous systems, where a well-defined neuronal pathway involving thermoreceptors on the surface of the skin communicate with the PreOptic area (POA) of the hypothalamus to regulate brown adipose tissue (BAT) activity. The POA acts as a thermostat, adjusting BAT activity to ensure proper adaptation to changes in ambient temperature. It is well known that neurons in the POA are temperature sensitive and directly modulate BAT activity. However, recent findings show that light may also regulate this pathway. Opsins are a family of G-protein coupled receptors (GPCRs) that can convert photon energy from light into cellular signals. We show that neurons in the POA express opsin-5 (OPN5), a non-visual opsin found in various extra-retinal tissues and known to respond to violet wavelengths (_max = 380 nm). Mice lacking Opn5 show an exaggerated response to cold stimuli and have elevated body temperatures. Additionally, depriving wild-type mice of violet light from birth produces a similar cold defense phenotype. While the neuronal identity of POA thermogenesis neurons are well understood, it is not understood whether OPN5 POA neurons are stimulatory or inhibitory. Our results characterize a population of POA neurons that express Opn5 and suggest a mechanism whereby the mammalian thermoregulatory apparatus is light responsive.