Abstract
Purpose: :
To characterize the mouse mutant Pedv/128, a partial loss of function of PdgfrB, as a possible model for Diabetic Retinopathy and as a tool for investigating the role of pericytes in maintaining a normal retinal vasculature.
Methods: :
The mutant line Pedv/128 was identified during a recessive ENU mutagenesis screen at MRC Harwell, with blood in the eyes and was named redeye. Haplotype mapping followed by exome sequencing identified the gene mutated. Subsequently, detailed histological analysis on eye sections and immunohistochemistry on wholemount retinas were carried out to determine the effect of the mutation on the retinal vasculature. Vascular permeability assays were also performed to determine the extent of the vessel leakage.
Results: :
A donor splice site mutation was identified in Pdgfrb which caused partial loss of normal splicing resulting in a frameshift and premature termination. Consequently there is a substantial reduction in expression of the normal Pdgfrb transcript. PDGF is an important regulator of embryological development, cell proliferation, migration and survival. PDGFB/PDGFRB signalling is required for pericyte recruitment to developing blood vessels in order to confer vessel stability and more recently has been implicated in the formation of the Blood Brain Barrier (BBB). We find that that the redeye strain exhibits vascular leakage due to a defect in pericyte recruitment, that is confined to the central nervous system (CNS). Consequently there is defective vessel patterning and vessel tortuousity, reduced basement membrane deposition as well as changes in the expression of BBB markers.
Conclusions: :
Loss of function mutants of Pdgfrb are usually embryonic lethal due to severe haemorrhaging. Unusually, the redeye mutant mice are viable, with only the CNS vasculature affected. They are therefore a better model for diseases involving pericyte deficiencies such as Diabetic Retinopathy than those currently being used. In addition, the defect in BBB development makes them a useful tool for dissecting the role of pericytes in BBB formation and vascular development.
Keywords: development • pathobiology • diabetic retinopathy