Characterization of Circadian Components in a newly transformed rat retinal ganglion cell line (RGC-5)

NIETO PAULA S; GUIDO MARIO E

Buenos Aires, Argentina

Simposio; VII Latin American Symposium of Chronobiology (LASC); 2005

In vertebrates, the circadian system that controls many physiological and behavioural rhythms includes the retina, which is responsible for photoreception and for synchronizing endogenous clocks to environmental lighting conditions. The retina is itself rhythmic, generating daily rhythms in melatonin production and gene expression. We found that RGCs are autonomous circadian oscillators synthesizing Melatonin: in vivo experiments demonstrate that chick RGCs synthesize a melatonin with levels peaking during the day. In addition cultures of purified embryonic retinal ganglion cells (eRGCs) biosynthesize melatonin from a radioactive precursor with a significant daily variation and show a circadian rhythm in the expression of AA-NAT, a key enzyme in the biosynthesis of this compound (Garbarino et al, 2004). By other hand, recently, Dr. Agarwal’s laboratory establishes a clonal RGCs line from virally transformed dispersed postnatal rat retinal cells. This retinal ganglion cell line (RGCs-5) has a certain characteristics of retinal ganglion cells based on Thy-1 and Brn-3c expression and its sensitivity to glutamate exitotoxicity and neurotrophin withdrawal (Krishnamoorthy et al., 2001). Thus the RGCs-5 cell line appears be useful to study various aspects of RGC biology including its characteristics of autonomous circadian oscillators. RESULTS.The principal aim of this work was to characterize in this cell line ( kindly gifted for Dr. Agarwal) the expression of circadian components of central clock like Per, Cry, Bmall and Clock proteins and study the ability of synthesizing Melatonin and Photosensitivity responsiveness . Preliminarily results show that RGCs-5 line expresses Per1 protein with high levels during the first hours after a synchronizing serum shock stimulus and that a light pulse induces the expression of c-Fos protein in this newly cells line