Role of Fibulins 2 and 5 in Retinal Development and Maintenance.

Fibulins 2 and 5 are part of a seven-member family of proteins integral to the retinal extracellular matrix. Our study aimed to further explore the roles of both fibulins in retinal function. We obtained knockout mouse models of both fibulins and performed immunohistochemistry, electroretinography, and histology to investigate the outcome of eliminating these proteins. Immunohistochemical analysis showed that both fibulins are localized to the RPE, choroid, and Bruch's membrane. Functional testing showed a significantly reduced scotopic A response at 1 month of age, when compared to their wild-type counterpart. This functional reduction remained constant throughout the age of the animal and only declined as a result of normal aging. The functional decline was associated with reduced number of photoreceptor cells. The results presented clearly demonstrate that fibulins 2 and 5, as extracellular proteins, are necessary for normal retinal development.