| 1. |
- Looman, Camilla, et al.
(author)
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An activating mutation in the PDGF receptor-beta causes abnormal morphology in the mouse placenta
- 2007
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In: International Journal of Developmental Biology. - : UPV/EHU Press. - 0214-6282 .- 1696-3547. ; 51:5, s. 361-370
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Journal article (peer-reviewed)abstract
- An oncogenic D842V mutation in the platelet-derived growth factor (PDGF) alpha-receptor (Pdgfra) has recently been described in patients with gastrointestinal stromal tumors. In order to test if the same mutation would confer oncogenic properties to the homologous PDGF beta-receptor (Pdgfrb), the corresponding aspartic acid residue at position 849 of Pdgfrb was changed into valine (D849V) using a knock-in strategy. This mutation turned out to be dominantly lethal and caused death even in chimeras (from 345 transferred chimeric blastocysts, no living coat chimeras were detected). Experiments employing mouse embryonic fibroblasts (MEFs) indicated hyperactivity of the mutant receptor. The mutant receptor was phosphorylated in a ligand-independent manner and, in contrast to wild-type MEFs, mutant cells proliferated even in the absence of ligand. Knockout experiments have previously indicated a role for Pdgfrb in placental development. We therefore analyzed wild-type and Pdgfrb D849V chimeric placentas from different gestational stages. No differences were detected at embryonic days 11.5 and 13.5 (n=4). At embryonic day 17.5, however, chimeric placentas (n=3/4) displayed abnormalities both in the labyrinth and in the chorionic plate. The changes included hyper-proliferation of alpha-smooth muscle actin and platelet/endothelial cell adhesion molecule-1 positive cells in the labyrinth and cells in the chorionic plate. In addition, the fetal blood vessel compartment of the labyrinth was completely disorganized.
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| 2. |
- Magnusson, Peetra U., et al.
(author)
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Platelet-derived growth factor receptor-beta constitutive activity promotes angiogenesis in vivo and in vitro
- 2007
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In: Arteriosclerosis, Thrombosis and Vascular Biology. - 1079-5642 .- 1524-4636. ; 27:10, s. 2142-2149
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Journal article (peer-reviewed)abstract
- OBJECTIVE - Knockout studies have demonstrated crucial roles for the platelet-derived growth factor-B and its cognate receptor, platelet-derived growth factor receptor-β (PDGFR-β), in blood vessel maturation, that is, the coverage of newly formed vessels with mural cells/pericytes. This study describes the consequences of a constitutively activating mutation of the PDGFR-β (Pdgfrb) introduced into embryonic stem cells with respect to vasculogenesis/angiogenesis in vitro and in vivo. METHODS AND RESULTS - Embryonic stem cells were induced to either form teratomas in vivo or embryoid bodies, an in vitro model for mouse embryogenesis. Western blotting studies on embryoid bodies showed that expression of a single allele of the mutant Pdgfrb led to increased levels of PDGFR-β tyrosine phosphorylation and augmented downstream signal transduction. This was accompanied by enhanced vascular development, followed by exaggerated angiogenic sprouting with abundant pericyte coating as shown by immunohistochemistry/immunofluorescence. Pdgfrb embryoid bodies were characterized by increased expression of vascular endothelial growth factor (VEGF)-A and VEGF receptor-2; neutralizing antibodies against VEGF-A/VEGF receptor-2 blocked vasculogenesis and angiogenesis in mutant embryoid bodies. Moreover, Pdgfrb embryonic stem cell-derived teratomas in nude mice were more densely vascularized than wild-type teratomas. CONCLUSION - Increased PDGFR-β kinase activity is associated with elevated expression of VEGF-A and VEGF receptor-2, acting directly on endothelial cells and resulting in increased vessel formation.
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| 3. |
- Singh, Umashankar, et al.
(author)
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Expression and Function of the Gene Encoding the Voltage-Dependent Calcium Channel β3-Subunit in the Mouse Placenta
- 2007
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In: Placenta. - : Elsevier BV. - 0143-4004 .- 1532-3102. ; 28:5-6, s. 412-420
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Journal article (peer-reviewed)abstract
- Voltage-dependent Ca(2+) channels (VDCC) exist in most excitable cells and their properly regulated activity is essential for critical biological processes as many of these are sensitive to cellular Ca(2+) ion concentration. The ancillary cytoplasmic Ca(2+) channel beta subunits (CACNB) modulate Ca(2+) channel function and are required to enhance the number of functional channels in the plasma membrane. There are four genes encoding CACNB subunits and the gene encoding CACNB3 is over expressed in hyperplastic placentas of mouse interspecies hybrids. To determine the role of CACNB3 in the mouse placenta, we performed an expression and function analysis. Our results show that Cacnb3 exhibits specific spatial and temporal expression in the mouse placenta. Deletion of Cacnb3 does not produce a strong placental phenotype, which may be due to expression of other CACNB subunit encoding genes; however, sporadic occurrence of a labyrinthine architecture phenotype, characterized by reduced density of fetal blood vessels and decrease in pericyte number, could be observed. Down-regulation of Cacnb3 expression did not rescue placental hyperplasia in a model of interspecies hybrid placentas, which indicates that up-regulation in the hyperplastic placentas is a downstream event.
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