Journal of Neuroscience, Vol 11, 3531-3538, Copyright © 1991 by Society for Neuroscience
Spectrin isoforms in the mammalian retina
T Isayama, SR Goodman and IS Zagon
Department of Neuroscience and Anatomy, Pennsylvania State University, M. S. Hershey Medical Center, Hershey 17033.
Spectrin is a major component of the mammalian neuronal cytoskeleton. In
the CNS, three isoforms of brain spectrin are known to exist: a cellular
and dendritic isoform, (240/235E), related to neurons and glia; a cellular
and axonal isoform, (240/235), related to neurons; and an isoform specific
for astrocytes, (240/235A). In the present study, brain spectrins
(240/235E) and (240/235) were localized within the mouse retina and optic
nerve. Immunoblot analyses of proteins isolated from mouse retinas
utilizing polyclonal antibodies to either brain spectrin (240/235) or brain
spectrin (240/235E) revealed that these spectrins are present in the retina
and that the two isoforms are the same molecular weights as those found in
the brain. Immunocytochemical studies revealed that spectrin (240/235E) was
localized in cell bodies of the inner nuclear, outer nuclear, and ganglion
cell layers, and processes arborizing within the inner and outer plexiform
layers. Spectrin (240/235) was distributed diffusely within the retina,
lightly staining neurons in both the inner nuclear and outer nuclear
layers, and the ganglion cell layer. In contrast to the situation found in
the brain, spectrin (240/235) was but one of the axonal forms in the
retina. We found that spectrin (240/235E) was also present in the axon-
rich fiber layer and in the optic nerve and was often associated with
fibrous elements. Spectrin (240/235) was also detected in the nerve fiber
layer and optic nerve, but this isoform was not localized to
fibers.(ABSTRACT TRUNCATED AT 250 WORDS)