The impact of light and clocks on physiology and behavior

6TH OCTOBER 2017 - 1 PM

Kristin Tessmar, Max F. Perutz Laboratories (MFPL), Vienna, Austria.

Summary: The work in my lab focuses on the impact of light on animal nervous systems, the mechanisms of endogenous clocks and their evolution. These different aspects are partially interconnected as light functions as a zeitgeber for these clocks. The marine bristle worm Platynereis dumerilii harbors a light-entrained circadian, as well as a monthly (circalunar) clock. In order to study the molecular and cellular nature of its circalunar clock, as well as its interaction with the circadian clock, we have established transient and stable transgenesis, inducible specific cell ablations, chemical inhibitors, as well as TALEN-mediated genome engineering. We investigated the extent of transcript change in the brain caused by the circalunar clock and compare this change to other major conditions (sex determination, maturation) occurring during the life of the worm, as well as to the known extent of transcript change caused by the circadian clock. We furthermore follow the question, how the worm’s different light receptors sense solar vs. lunar light to entrain its respective circadian and circalunar clocks. For this we investigate light receptors inside and outside (non-visual) the eyes.

Non-visual photoreceptors also exist in vertebrates. In fact, light perception by cells in the inner brain of vertebrates, independent of eyes and pineal organs, was already discovered more than 100 years ago. The responsible encephalic photoreceptors have been thought to be specialized cells, similar to the photoreceptors present in the eye and pineal. Consistently, the expression of several opsins has been described at places harboring such deep brain photoreceptors, and hence these opsins were independently claimed to mediate non-visual light responses, such as seasonality. During recent years, an impressive number of non-visual opsins was identified and shown to be in principle able to function as light receptors. Their complexity is particularly high in teleost fish. In order to obtain a better understanding of this puzzling complexity, we investigate several ‘non-visual’ Opsins on a functional level. Our particular focus is on TMT/Encephalopsin group, since these Opsins exhibit a particularly slow sequence evolution and some members are conserved across all vertebrate phyla.

Location: Amphi Charpak, tower 22, ground floor, Jussieu Campus.