Mice Lacking Platelet-Derived Growth Factor D Display a Mild Vascular Phenotype

Platelet-derived growth factor D (PDGF-D) is the most recently discovered member of the PDGF family. PDGF-D signals through PDGF receptor β, but its biological role remains largely unknown. In contrast to other members of the PDGF family of growth factors, which have been extensively investigated using different knockout approaches in mice, PDGF-D has until now not been characterized by gene inactivation in mice. Here, we present the phenotype of a constitutive Pdgfd knockout mouse model (Pdgfd^-/-), carrying a LacZ reporter used to visualize Pdgfd promoter activity. Inactivation of the Pdgfd gene resulted in a mild phenotype in C57BL/6 mice, and the offspring was viable, fertile and generally in good health. We show that Pdgfd reporter gene activity was consistently localized to vascular structures in both postnatal and adult tissues. The expression was predominantly arterial, often localizing to vascular bifurcations. Endothelial cells appeared to be the dominating source for Pdgfd, but reporter gene activity was occasionally also found in subpopulations of mural cells. Tissue-specific analyses of vascular structures revealed that NG2-expressing pericytes of the cardiac vasculature were disorganized in Pdgfd^-/- mice. Furthermore, Pdgfd^-/- mice also had a slightly elevated blood pressure. In summary, the vascular expression pattern together with morphological changes in NG2-expressing cells, and the increase in blood pressure, support a function for PDGF-D in regulating systemic arterial blood pressure, and suggests a role in maintaining vascular homeostasis.     

In vivo suppression of phytochrome aggregation by the GroE chaperonins in Escherichia coli

When expressed in Escherichia coli, a truncated form of phytochrome (oat PHYA AP3 residues 464-1129) self associates to form a series of products ranging in size from monomers to aggregates of greater than 20 subunits. When these same phytochrome sequences are coexpressed with the chaperonins GroEL and GroES, the truncated phytochrome migrates as a native-like dimer in size exclusion chromatography and no higher-order aggregates were detected. GroEL and GroES inhibition of phytochrome aggregation in E. coli presumably occurs via the suppression of folding pathways leading to incorrectly folded phytochrome.