Journal of Neuroscience, Vol 11, 1470-1477, Copyright © 1991 by Society for Neuroscience
A monoclonal antibody that distinguishes between temporal and nasal retinal axons
SC McLoon
Department of Cell Biology and Neuroanatomy, University of Minnesota, Minneapolis 55455.
A monoclonal antibody was developed that recognizes an antigen with an
asymmetric distribution in the chick retina. Immunohistochemistry showed
that this antigen, temporal retinal axon protein (TRAP), was present on
most if not all axons that arose from the temporal side of the retina. Very
few of the axons from the nasal side of the retina were positive for TRAP.
The nasal-temporal difference appeared to be in the number of axons that
stained with this antibody rather than in the intensity of staining. The
transition between nasal and temporal retina based on TRAP distribution
appeared to be a vertical line centered on the optic fissure. A
competition-based ELISA was developed to quantify the average amount of
TRAP on axons in different regions of the retina. This assay also suggested
that the pattern of TRAP distribution across the retina was a step
function, though the results did not completely rule out the possibility of
a continuous concentration gradient oriented circumferentially around the
retina. Explants of embryonic nasal and temporal retina had a similar
dichotomy in TRAP expression during the first 1 or 2 d in culture. The
antibody to TRAP bound to retinal neurites in culture without the cell
membrane being made permeable, which suggests that TRAP is a cell-surface
molecule. In culture, TRAP was also expressed on the growth cones.
Immunoblots showed that TRAP is trypsin sensitive and has an approximate
molecular mass of 135 kDa. This is the first molecule identified with an
asymmetric distribution in the nasal-temporal axis of the retina.(ABSTRACT
TRUNCATED AT 250 WORDS)
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