CIQUIBIC   05472
CENTRO DE INVESTIGACIONES EN QUIMICA BIOLOGICA DE CORDOBA
Unidad Ejecutora - UE
congresos y reuniones científicas
Título:
NOVEL VISUAL CYCLE IN THE CHICKEN INNER RETINA
Autor/es:
DIAZ, N.; VERRA D; BETTS B S; VALDEZ D J; TSIN A; MARIO E. GUIDO
Lugar:
Fort Lauderdale, Florida, EEUU.
Reunión:
Encuentro; Annual meeting Association for Research in Vision and Ophthalmology (ARVO); 2012
Institución organizadora:
Association for Research in Vision and Ophthalmology (ARVO)
Resumen:
Purpose: In previous studies, we demonstrated the presence of intrinsically
photosensitive retinal ganglion cells (ipRGCs) expressing the photopigment melanopsin
in the wild type (WT) chicken retina as well as light responses mediated by the inner
retina of GUCY1* (blind) birds (Contin et al., 2006, 2010; Valdez et al., 2009; Verra et
al 2011). Therefore, bistable photopigments presumably responsible for photosensitivity
may use a novel visual cycle for chromophore regeneration that relies upon distinct
isomerases through light-dependent or -independent processes (Wang et al., 2010).
In the present study, we investigated the expression of the photoisomerase RGR and
zebrafish RPE65c (cone cycle isomerase, Takahashi et al., 2011) as well as the activity
of visual cycle enzymes and levels of retinal chromophores (11-cis RAL and all-trans RAL) in the inner retina of WT birds.
Methods: Dark-adapted young WT chickens were exposed to a 30 min light pulse
(2000 lux) or kept in the dark and sacrificed under dim red light. Eyes were dissected
and lyophilized, and the inner retina or different cell layers (ganglion cell layer: GCL,
inner nuclear layer: INL) obtained by the Scotch tape method (Guido et al., 2001).
Samples were processed for RNA extraction, RT-PCR, immunochemical (RPE65c
antibody from Dr. Ma at UOHSC) or enzyme activity assays. Retinoids extracted were
analyzed by HPLC.
Results: Levels of 11-cis RAL were higher in the GCL and INL samples from lightadapted birds as compared with levels of all-trans RAL which were higher in the
dark samples. Also, we observed the presence of RGR and RPE65c-like protein in
different inner retinal cell layers: RGR in the GCL while RPE65c-like protein in the
INL and IPL. Isomerase activity was found in the INL only while acyl CoA:retinol
acyltransferase (ARAT) was observed in both INL and GCL.
Conclusions: These results demonstrate that in the chicken, different inner retinal cell
layers differentially express RGR and RPE65c-like protein and selectively display
enzyme activities for the isomerase and ARAT. The different light-dark effects on
retinoids and the differential distribution of photoisomerases present in the retina
strongly suggest that light-induced isomerization of retinal in the chicken inner retina
differs from those described in the classical and cone-visual cycles. These results
suggest that a novel visual cycle exists in the chicken inner retina to support retinoid
isomerization in ipRGCs or other photosensitive cells.