Phenotypic Analysis of Aged Mice Containing a Targeted Deletion of the Gene Encoding Complement Factor H

Abstract

Purpose: : The Y402H polymorphism in complement factor H is linked to susceptibility to age–related macular degeneration (AMD). The aim of this study was to establish whether complete deletion of the CFH gene results in a phenocopy of AMD in mice.

Methods: : Using a multidisciplinary approach, we have evaluated retinal structure and function in 2 year old CFH null mutant and age–matched wild type mice. Animals were phenotyped using a wide range of techniques to differentiate between age–related changes and those linked specifically to the absence of CFH. Functional assessment included behavioural visual acuity and contrast sensitivity measurements, fluorescein angiography (FA), and electroretinography (ERG) for rod/cone function. In vivo stuctural studies were performed by retinal imaging using fundus photography and high resolution confocal scanning laser ophthalmoscopy (autofluorescence and red–free). Following functional analysis, eyes were fixed and sectioned, and retinae, Bruch’s membrane and choroid were examined by immunohistochemistry using a combination of light and confocal microscopy, and transmission electron microscopy (EM).

Results: : Mice lacking CFH had significantly reduced visual acuity than age–matched controls, and ERG a– and b–wave amplitudes were reduced at high stimulus intensities (> –1 Log unit). Abnormalities in the appearance of the fundus were noted in the CFH knock out animals, including an apparently deeper location of autofluorescent deposits. No differences were observed between the CFH knock out (KO) and wild type mice with regard to FA. Histopathological analysis revealed that there was less subretinal pigment epithelial banded material reminiscent of basal laminar deposit in the CFH KO mice, and that Bruch’s membrane appeared thinner. EM revealed apparent ultrastructural disorganisation at the rod outer segment–pigment epithelial interface .

Conclusions: : These results provide evidence that CFH is required for the maintenance of a healthy retina, and suggest that mouse models of CFH deficiency/polymorphism may be useful in understanding the pathogenesis of AMD.

Keywords: age-related macular degeneration • transgenics/knock-outs • degenerations/dystrophies