Abstract
Purpose: :
Neurturin (NRTN) is a member of the glial cell line-derived neurotrophic factor (GDNF) family. We have shown previously that NRTN deficiency in mice is associated with abnormal extension of horizontal cell and bipolar cell processes into the outer nuclear layer of the retina as well as a severely disrupted outer plexiform layer, with very sparse horizontal cell dendrites and axons. Dye-labeling of individual horizontal cells demonstrated a significant reduction in dendritic branch points in the NRTN-/- retinas compared to wild-type retinas. These studies suggest that mice lacking NRTN-mediated signaling have disrupted development and arborization of horizontal cell processes. The purpose of this study is to determine if horizontal cell density is also altered in retinas of NRTN-/- mice compared to wild type mice.
Methods: :
Whole mount preparations of two month-old wild type (n=14) and NRTN-/- (n=8) mouse retinas were immunostained with an anti-calbindin antibody to label horizontal cells. To count the horizontal cells, each whole-mount quadrant was divided into central and peripheral zones. Fluorescent microscopy at 20X was used to sample three evenly-spaced fields per zone for a total of six fields per quadrant and 24 fields per retina. Images were processed with Metamorph and cells counted with automated software.
Results: :
The mean horizontal cell density in the NRTN-/- retinas was 278 cells per mm2 compared to 899 cells per mm2 in wild type retinas (p=2.65x10-10). There was no difference in mean horizontal cell density in central versus peripheral retina in either group of mice.
Conclusions: :
This study demonstrates a significant reduction in the horizontal cell density in retinas of NRTN-/- mice compared to wild-type mice. These data, along with the abnormal horizontal cell morphology previously observed in NRTN-/- mice, suggest that NRTN-mediated signaling plays a crucial role in horizontal cell development.
Keywords: retinal development • horizontal cells