Early appearance of non-visual and circadian markers in the developing inner retinal cells of chicken

DIAZ NM; MORERA LP; VERRA DM; CONTIN MA; GUIDO ME

BioMed Res International (ex J Biomedicine and Biotechnol)

Hindawi Publishing Corporation

Lugar: Akron, Ohio; Año: 2014 p. 1 - 9

2314-6133

The retina is a key component of the vertebrate circadian system; it is responsible for detecting and transmitting the environmental illumination conditions (day/night cycles) to the brain, that synchronize the circadian clock located in the suprachiasmatic nucleus (SCN).  For this, retinal ganglion cells (RGCs) project to the SCN and other non-visual areas. In the chicken, intrinsically photosensitive RGCs (ipRGCs) expressing the photopigment melanopsin (Opn4) transmit photic information and regulate diverse non-visual tasks. In non-mammalian vertebrates, two genes encode Opn4: the Xenopus (Opn4x) and the mammalian (Opn4m) orthologs. RGCs express both Opn4 genes but are not the only inner retinal cells expressing Opn4x: horizontal cells (HCs) also do so. Here, we further characterize primary cultures of both populations of inner retinal cells (RGCs and HCs) expressing Opn4x. The expression of this non-visual photopigment, as well as that for different circadian markers such as the clock genes Bmal1, Clock, Per2 and Cry1, and the key melatonin synthesizing enzyme, arylalkylamine N-acetyltransferase (AA-NAT), appears very early in development in both cell populations. The results clearly suggest that non-visual Opn4 photoreceptors and endogenous clocks converge all together in these inner retinal cells at early developmental stages.