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Immunocytochemical localization of CD44 in the mouse retina
M H Chaitin1, H S Wortham, A M Brun-Zinkernagel
1Department of Anatomy and Cell Biology, University of North Texas Health Science Center at Fort Worth 76107.
Insights
The transmembrane glycoprotein CD44 is found on Müller cell microvilli in the mouse retina. This molecule may be crucial for attaching the neural retina to the interphotoreceptor matrix.
Area of Science:
- Ophthalmology
- Cell Biology
- Neuroscience
Background:
- CD44 is a transmembrane glycoprotein and cell adhesion molecule.
- It mediates cell attachment to extracellular matrix and binds to the actin cytoskeleton.
- CD44's role in retinal cell adhesion is not fully understood.
Purpose of the Study:
- Investigate the presence and distribution of CD44 in the mouse retina.
- Determine if CD44 is important for retinal cell adhesion.
- Clarify the specific localization of CD44 within retinal structures.
Main Methods:
- Immunoperoxidase techniques for light microscopy.
- Cryoultramicrotomy and immunogold labeling for ultrastructural localization.
- Western blotting to confirm antibody specificity and protein molecular weight.
Main Results:
- CD44 labeling observed at the outer limiting membrane and adjacent region.
- Cryoultramicrotomy and immunogold labeling revealed CD44 specifically on Müller cell microvilli.
- Western blot confirmed a ~90 kDa protein recognized by the anti-CD44 antibody.
Conclusions:
- CD44 is localized to Müller cell microvilli in the mouse retina.
- CD44 may mediate the attachment of the neural retina to the interphotoreceptor matrix.
- This finding highlights a potential role for CD44 in maintaining retinal structure and function.
Abstract:
The transmembrane glycoprotein CD44 is a cell adhesion molecule which has recently been localized in a variety of cell types. It mediates cell attachment to extracellular matrix components and also binds to the actin cytoskeleton within the cell. In this study, the presence and distribution of CD44 in the mouse retina was investigated in order to determine whether this molecule might be important for retinal cell adhesion. With immunoperoxidase techniques, positive labeling for CD44 was found at the level of the outer limiting membrane and in the region just sclerad to it. However, from these light microscope results it was not clear if the label was in the photoreceptor inner segments, the Müller cell apical microvilli, or both. In order to answer this question, cryoultramicrotomy and immunogold labeling were used to demonstrate that CD44 is specifically localized to the Müller cell microvilli which appose the interphotoreceptor matrix. Western blotting of a retina homogenate showed that the anti-CD44 antibody is specific for a protein of approximately 90 kDa which is the correct molecular weight for the most abundant form of CD44. These results, along with the known binding characteristics of CD44 for the extracellular matrix, suggest that CD44 could play a role in mediating the attachment of the neural retina to components of the interphotoreceptor matrix.