Abstract
Purpose :
The ability to detect and track moving objects is a fundamental function of the visual system. In mouse and rabbit Special AT-rich binding protein 2 (Satb2) is expressed by direction selective retinal ganglion cells (Sweeney et al., 2017; Dhande et al., 2018). The existence of direction selective ganglion cells (DS-GCs) in primate retina is however under debate. Here we asked whether SatB2 expressing ganglion cells with mouse-homologous morphology are present in macaque and human retina.
Methods :
Retinas from two adult male macaque (M. fasciularis) monkeys were obtained from Monash University. One post mortem human retina (from a 52 year old male) was obtained from the Lions NSW Eyebank. Retinas were immersion fixed in paraformaldehyde and immuno-labelled with antibodies against Satb2 and choline acetyl transferase (ChAT). The Satb2 labelled cells were injected with the lipophilic dye DiI. Other retinal pieces were processed for double label immunohistochemistry with antibodies against SATB2 and the ganglion cell marker RBPMS, or with SATB2 and antibodies against melanopsin.
Results :
In macaque peripheral retina the Satb2 positive cells make up on average 3.2% of all ganglion cells. Their density falls from 277 cells/mm2 at 2 mm to 16 cells/mm2 at 9 mm eccentricity. The Satb2 cells have large dendritic field diameters (increasing from 150 µm at 1.8 mm to 860 µm at 6.5 mm eccentricty). Satb2 cells stratify either above or below the ChAT bands and in macaque retina comprise four morphological types including large bistratified (n = 6), narrow thorny Off (n = 7) and large sparse cells (On and Off, n = 26). Double labeling showed that Satb2 cells do not include melanopsin-expressing ganglion cells. In human retina, 11 cells were analyzed. All cells were classified as large sparse Off cells and had dendritic field diameters ranging between 420 and 680 µm.
Conclusions :
Satb2 is expressed by ganglion cell types in macaque and human retina with a morphology clearly different from direction selective cells in rabbit and mouse. We conclude that Satb2 expression in direction selective ganglion cells is not preserved between primates and other mammalian orders.
This abstract was presented at the 2019 ARVO Annual Meeting, held in Vancouver, Canada, April 28 - May 2, 2019.