Sapède, D., Chaigne, C., Blader, P., & Cau, E. (2020). Functional heterogeneity in the pineal projection neurons of zebrafish. Molecular and Cellular Neuroscience, 10, 103468.
The zebrafish pineal organ is a photoreceptive structure containing two main neuronal populations (photoreceptors and projections neurons). Here we describe a subpopulation of projection neurons that expresses the melanopsin gene, opn4xa. This new pineal cell type, that displays characteristics of both projection neurons and photoreceptors, share a similar dependency for BMP and Notch signalling pathways with classical non-photosensitive projection neurons (PN). Functionally, however, whereas classical, opn4xa–negative PNs display an achromatic LIGHT OFF response, the novel cell type we describe exhibit a LIGHT ON character that is elicited by green and blue light. Taken together, our data suggest a previously unanticipated heterogeneity in the projection neuron population in the zebrafish pineal organ raising the question of the importance of these differences in pineal function.
Melanopsin; ipRGCs; Pineal gland; Photoreceptor