The Journal of Neuroscience, February 15, 2003, 23(4):1383
Ectopic Photoreceptors and Cone Bipolar Cells in the Developing
and Mature Retina
Emine
Günhan1,
Deborah
van der List1, and
Leo M.
Chalupa1, 2
1 Section of Neurobiology, Physiology, and Behavior,
Division of Biological Sciences, and 2 Department of
Ophthalmology, School of Medicine, University of California, Davis,
California 95616
An antibody against recoverin, the calcium-binding
protein, labels photoreceptors, cone bipolar cells, and a subpopulation of cells in the ganglion cell layer. In the present study, we sought to
establish the origin and identity of the cells expressing recoverin in
the ganglion cell layer of the rat retina. By double labeling with
rhodopsin, we demonstrate that early in development some of the
recoverin-positive cells in the ganglion cell layer are photoreceptors.
During the first postnatal week, these rhodopsin-positive cells are
eliminated from the ganglion cell layer, but such neurons remain in the
inner nuclear layer well into the first postnatal month. Another
contingent of recoverin-positive cells, with morphological features
equivalent to those of bipolar cells, is present in the postnatal
retina, and ~50% of these neurons survive to maturity. The incidence
of such cells in the ganglion cell layer was not affected by early
transection of the optic nerve, a manipulation that causes rapid loss
of retinal ganglion cells. These recoverin-positive cells were not
double-labeled by cell-specific markers expressed by photoreceptors,
rod bipolar cells, or horizontal and amacrine cells. Based on
their staining with recoverin and salient morphological features, these
ectopic profiles in the ganglion cell layer are most likely cone
bipolar cells. Collectively, the results provide evidence for
photoreceptors in the ganglion cell and inner nuclear layers of the
developing retina, and a more permanent subpopulation of cone bipolar
cells displaced to the ganglion cell layer.
Key words:
ectopic cells; recoverin; bipolar cells; photoreceptors; retina; development
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