Distribution of Microtubule Associated Protein 2 (map-2) in the Human Retina

Abstract

Purpose:: To determine the distribution of MAP 2 in human retinas using immunohistochemistry.

Methods:: Human retinas were obtained from eyes previously used for cornea donation. Retinas were fixed in 4% paraformaldehyde in 0.1M phosphate buffer for 12h. Subsequently, retinas were dissected and the choroid and vitreous were removed. Retinal wholemounts were incubated in mouse anti-MAP 2 antibody for 72 hours (1:1000 ) at room temperature, and wholemounts were rinsed and incubated with a biotinylated goat anti-mouse antibody followed by the avidin-biotin-horseradish peroxidase complex for 12h each. Immunoreactivity was revealed by the standard diaminobenzidine method. The numbers of labeled cells and their retinal distribution were established with a camera lucida fitted to a microscope. We used a systematic sampling method to map the distribution along the entire retina at 2 mm intervals.

Results:: MAP-2 immunoreactivity revealed the presence of fibers and a subset of large ganglion cells with soma sizes > 150 µm² (somas ranging from 150 to 800 µm²) throughout the ganglion cell layer. These large ganglion cells were detected in highest density values around the foveola (250 cells/mm²). Densities decreased concentrically towards the retinal periphery. Isodensity contours also showed the presence of a slight elongation along the nasotemporal meridian.

Conclusions:: MAP 2 immunoreactivity revealed a specific population of large ganglion cells in the human retina and could be used as marker to characterize pathological alterations in this subset of ganglion cells.

Keywords: retina: neurochemistry • immunohistochemistry • ganglion cells