TMT-Opsins differentially modulate medaka brain function in a context-dependent fashion

Vertebrate behavior is strongly influenced by light. Photoreceptors, encoded by Opsins, are present inside the vertebrate brain and peripheral tissues. Their non-visual functions are largely enigmatic. We focus on tmt-opsin1b and 2, c-Opsins with ancestral-type sequence features, conserved across several vertebrate phyla and with partly similar expression. Their loss-of-function mutations differentially modulate medakafish behavior in a context-dependent manner. Specifically, differences in light conditions have differential effects depending on age and frequency of the light changes, part of which are mediated by TMT-Opsin1b acting outside the eyes, while the pre-pro-hormone sst1b is regulated by daylength via TMT-opsin1b in an eye-dependent manner. Analyses of tmt-opsin1b;tmt-opsin2 double mutants reveals partial complementation of single mutant behavioral and molecular phenotypes. Our work starts to disentangle the highly complex interactions of vertebrate non-visual Opsins, suggesting that tmt-opsin-expressing cells together with other Opsins provide detailed light information to the organism for behavioral fine-tuning.