Light-regulation of OPN3 in primary cultures of retinal neurons and Müller Cells

RIOS, M.N.; MARCHESE, N.A.; GUIDO, M.E.

Córdoba

Congreso; XXXIII Reunión Anual de la Sociedad Argentina de Investigación en Neurociencias; 2018

The avian retina is composed of different types of photoreceptors responsible for image and non-image forming tasks: visual photoreceptor cells (PRCs) cones and rods, melanopsinis expressing-intrinsically photoresponsiveretinal ganglion (ipRGCs) . In addition nonvisualopsinsOpn3 and Opn5 were shown to be expressed in the inner retina of vertebrates, responding to blue and UV light respectively. Opn3 is a nonvisualopsinGs-cupledprotein, its activation by blue light result in a cAMPincrease. The retina contains an endogenous circadian clock that temporally regulates its physiology and which is synchronized by light. Different molecular and cellular processes change along the day such as the neurohormonemelatonin which is synthesized in PRCs at night and in RGCs, in lower levels, during the day. The key enzyme in melatonin synthesis, ArylalkylamineN-acetyltransferase(AANAT) is expressed in PRCs, RGCs and HCs of the chicken retina while mRNA levels and activity for this enzyme are controlled by cAMPand the circadian clock. To investigate expression and light regulation of Opn3 in the developing retina, we evaluated their expression at different embryonic (E) days and in primary cultures of neuronal and glialcells, and their light responses by PCR and immunochemistry. AANAT mRNA and protein appeared as early as E6-8 in the developing RGC layer and later in inner retinal cells, while Opn3 and Opn5 traces were detected at those stages in RGCs, amacrineand glialcells, and a significant increase was seen by E10 and later on. In postnatal retinas, a clear light/dark difference was foundin AANAT, Opn3 and Opn5 proteins with higher values in the inner retina during the light phase. Moreover, AANAT and Opn3 were found in RGCs cultures while this opsinwas also seen in Muller cells. In addition, blue light increased AANAT expression in RGCs and Opn3 in Muller cells, and it also promoted a change in the subcellularlocalization and levels of this opsinin neuronal cells. Taken together, results show a spatiotemporal relationship between AANAT and OPN3 in inner retinal cells at the light phase suggesting an important role during the day.