Canine retina has a primate fovea-like bouquet of cone photoreceptors which is affected by inherited macular degenerations.
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Retinal areas of specialization confer vertebrates with the ability to scrutinize corresponding regions of their visual field with greater resolution. A highly specialized area found in haplorhine primates (including humans) is the fovea centralis which is defined by a high density of cone photoreceptors connected individually to interneurons, and retinal ganglion cells (RGCs) that are offset to form a pit lacking retinal capillaries and inner retinal neurons at its center. In dogs, a local increase in RGC density is found in a topographically comparable retinal area defined as the area centralis. While the canine retina is devoid of a foveal pit, no detailed examination of the photoreceptors within the area centralis has been reported. Using both in vivo and ex vivo imaging, we identified a retinal region with a primate fovea-like cone photoreceptor density but without the excavation of the inner retina. Similar anatomical structure observed in rare human subjects has been named fovea-plana. In addition, dogs with mutations in two different genes, that cause macular degeneration in humans, developed earliest disease at the newly-identified canine fovea-like area. Our results challenge the dogma that within the phylogenetic tree of mammals, haplorhine primates with a fovea are the sole lineage in which the retina has a central bouquet of cones. Furthermore, a predilection for naturally-occurring retinal degenerations to alter this cone-enriched area fills the void for a clinically-relevant animal model of human macular degenerations.
author list (cited authors)
Beltran, W. A., Cideciyan, A. V., Guziewicz, K. E., Iwabe, S., Swider, M., Scott, E. M., ... Aguirre, G. D
complete list of authors
Beltran, William A||Cideciyan, Artur V||Guziewicz, Karina E||Iwabe, Simone||Swider, Malgorzata||Scott, Erin M||Savina, Svetlana V||Ruthel, Gordon||Stefano, Frank||Zhang, Lingli||Zorger, Richard||Sumaroka, Alexander||Jacobson, Samuel G||Aguirre, Gustavo D