The development of blood vessels is dependent on several molecular cues to form properly. A functional PDGF-B/PDGFR-b signaling is paramount for the investment of mural cells, that provide with support, to the developing vasculature. Mutations in PDGFB and PDGFRB are linked to PFBC, an age-dependent neurodegenerative condition manifested by vessel associated calcifications in the brain. The overall aim of the work presented in here was to investigate PFBC related calcifications and analyze the effects of impaired PDGF-B/PDGFR-b signaling on the formation of brain calcifications in different mouse models. In paper I, we functionally analyzed PFBC-related PDGFB and PDGFRB mutations in vitro. While all PDGFB mutations lead to abolished protein function, PDGFRB mutations have more diverse consequences. We also show that reduced Pdgfb and Pdgfrb levels are insufficient for the formation of brain calcifications in several mouse strains. Moreover, region-specific susceptibility factors seem to reside in PFBC pathogenesis that are distinct from pericyte coverage and BBB deficiency. In paper II, we described the molecular composition and cellular association of calcified nodules that develop in two mouse models of PFBC, Pdgfbret/ret and Slc20a2-/- mice. We show that the nodules are composed of pro- and anti-mineralization proteins and that they are in direct association with astrocytes and microglia In paper III, we analyzed the effects of EC-specific ablation of PDGF-B in adult brain vasculature. We report a substantial decrease of pericyte coverage and altered VSMC morphology and that this phenotype is inadequate to trigger the formation of calcifications or affect BBB integrity. The aim of paper IV was to molecularly define the adult mouse brain vasculature by taking advantage of the scRNAseq technique. Here, we describe a gradual change in expression profile along the arteriovenous axis: ECs present a continuum along the axis while mural cell expression profile is punctuated. In summary, this thesis present detailed description of calcifications formed in mouse models of PFBC and address the role of impaired PDGF-B/PDGFR-b signaling for the formation of nodules in mice. Furthermore, the scRNaseq analysis performed on healthy adult brain vasculature has paved the way for future analysis in mouse models of PFBC
