GSE109102
Von Hippel-Lindau (VHL) mutations disrupt vascular patterning and maturation via Notch
Von Hippel-Lindau (VHL) gene mutations induce neural tissue hemangioblastomas as well as highly vascularized clear cell renal cell carcinomas (ccRCCs).  Pathological vessel remodeling arises from mis-regulation of hypoxia inducible factors and vascular endothelial growth factor, among other genes.  Variation in disease penetrance has long been recognized in relation to genotype. We show Vhl mutations also disrupt Notch signaling, causing mutation-specific vascular abnormalities e.g. type 1 (null) vs. type 2B (murine G518A representing human R167Q).  In conditional mutation retina vasculature, Vhl null mutation (i.e. UBCCreER/+; Vhlfl/fl) had little effect on initial vessel branching, but severely reduced arterial and venous branching at later stages.  Interestingly, this mutation accelerated arterial maturation, as observed in retina vessel morphology and aberrant a-smooth muscle actin localization, particularly in vascular pericytes.  RNA sequencing analysis identified gene expression changes within several key pathways including Notch and smooth muscle cell contractility. Notch inhibition failed to reverse later-stage branching defects but rescued the accelerated arterialization.  Retinal vessels harboring the type 2B Vhl mutation (i.e. UBCCreER/+; Vhlfl/2B) displayed stage-specific changes in vessel branching and an advanced progression toward an arterial phenotype.  Disrupting Notch signaling in 2B mutants increased both artery and vein branching, and restored arterial maturation toward non-mutant levels.  By revealing differential effects of the null and type 2B Vhl mutations on vessel branching and maturation, these data may provide insight into the variability of VHL-associated vascular changes, particularly the heterogeneity and aggressiveness in ccRCC vessel growth, as well as suggest Notch pathway targets for treating VHL syndrome. Overall design: A total of eight mouse retinas (n=8) were submitted for RNAseq. There are four experimental groups with 2 replicates for each: 1) WT CreER VHL lox/lox; 2)WT CreER VHL2b/lox; 3) UBC CreER VHL lox/lox; and 4) UBC CreER VHL2b/lox