DLL4 and retinal disorder: To directly test this prediction, we investigated the expression and distribution of dVenus, dll4 mRNA and protein as well as collagen IV empty sleeves formation in two different pathological systems with aberrant vascular patterning; the oxygen induced retinopathy (OIR) model, which reproduces aspects of the pathobiology of human retinopathies (Smith et al., 1994) and the glioblastoma brain tumour model (GBM).