Abstract
Purpose :
In human retina, the calcium binding protein calbindin is expressed by cone photoreceptors and subpopulations of bipolar, amacrine, and ganglion cells. Here, we used immunohistochemistry and intracellular injections to identify the calbindin expressing cells in the ganglion cell layer.
Methods :
Post mortem human donor eyes (n = 2) were obtained from the Lions NSW Eye Bank at Sydney Eye Hospital and fixed in 2% paraformaldehyde within 4 hours after death. Retinas were dissected out of the eye cup and processed as whole mounts or vertical sections. Double and triple labeling immunohistochemistry was performed using antibodies against calbindin, RBPMS (RNA binding protein with multiple splicing, expressed in ganglion cell somas), melanopsin (kindly provided by K.-W. Yau), and ChAT (choline acetyl transferase). In addition, whole mount retinas were prelabelled with antibodies against calbindin and fluorescent somas were subsequently targeted for DiI injections (Kao and Sterling, 2003) (n = 2 retinas). Images were taken using a Zeiss confocal microscope and cells were analyzed using Zen and Imaris software.
Results :
In the ganglion cell layer of peripheral retina about 4% (8/182) of the calbindin positive cells are positive for RBPMS and therefore are ganglion cells. DiI injections show that calbindin positive ganglion cells have large dendritic fields (diameter 600 to 640 µm) and a morphology corresponding to melanopsin-expressing ganglion cells. Double labeling confirmed that the somas of melanopsin expressing cells are calbindin positive. All outer stratifying (62/62), but only about half of the inner stratifying melanopsin-expressing (6/14) ganglion cells were calbindin positive. Double labeling of vertical sections with antibodies to calbindin and ChAT shows that all ChAT positive cells in the ganglion cell layer (25/25) but only 11% of ChAT cells (10/92) in the inner nuclear layer are calbindin positive.
Conclusions :
Inner and outer stratifying melanopsin expressing cells show differences in their expression of calbindin. Antibodies against ChAT label two immunohistochemical distinct populations of amacrine cells in the inner nuclear layer, but a single population in the ganglion cell layer.
This is an abstract that was submitted for the 2018 ARVO Annual Meeting, held in Honolulu, Hawaii, April 29 - May 3, 2018.