Abstract
Purpose: :
Fovin is expressed in the retina and is a member of the Tweety gene family. The Tweety gene products are proposed to be membrane channel proteins. In situ hybridization shows that fovin is expressed in the optic nerve. The goal of this study is to determine which cells in the optic nerve express fovin. This information will help us gain insight into fovin's function in the optic nerve.
Methods: :
Immunohistochemistry was performed on frozen tissue sections of rat optic nerve using a fovin antibody, DEBRH1–80, and a Cy3 labeled secondary antibody. Cell nuclei were identified by DAPI staining. In situ hybridization was also performed on frozen tissue sections. Fovin and myelin proteolipid protein (PLP) sense and antisense digoxigenin–labeled RNA probes were synthesized by in vitro transcription and hybridized to tissue sections of rodent optic nerve. PLP is a marker for oligodendrocytes.
Results: :
Longitudinal sections of the optic nerve were viewed on an epifluorescence microscope. Parallel wavy lines of immunoreactive material were seen with the fovin antibody. No labeling was observed with the preimmune control serum. In situ hybridization experiments show fovin expression in rows of adjacent cells along the long axis of the optic nerve, while hybridization is not seen with the fovin sense probe. This same hybridization pattern is also seen when the PLP antisense probe is hybridized to the optic nerve sections.
Conclusions: :
These experiments show that cells in the optic nerve express fovin mRNA and synthesize fovin protein. Fovin's amino acid composition and immunolocalization strongly suggest that fovin is a transmembrane protein. The cells expressing fovin are likely to be oligodendrocytes because the fovin and PLP probes hybridize to the same pattern of cells in the optic nerve. Oligodendrocytes are glia cells of the CNS that produce myelin. This myelin sheath surrounds axons and is essential for axonal function. As a transmembrane protein in oligodendrocytes, fovin may have an important role in glia–axon interactions that are vital for axonal maintenance and survival. Knowledge of fovin's localization will guide us to understanding fovin's role in oligodendrocyte cell homeostasis.
Keywords: immunohistochemistry • in situ hybridization • retinal glia