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- He, Liqun, et al.
(author)
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Analysis of the brain mural cell transcriptome
- 2016
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In: Scientific Reports. - : Springer Science and Business Media LLC. - 2045-2322. ; 6
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Journal article (peer-reviewed)abstract
- Pericytes, the mural cells of blood microvessels, regulate microvascular development and function and have been implicated in many brain diseases. However, due to a paucity of defining markers, pericyte identification and functional characterization remain ambiguous and data interpretation problematic. In mice carrying two transgenic reporters, Pdgfrb-eGFP and NG2-DsRed, we found that double-positive cells were vascular mural cells, while the single reporters marked additional, but non-overlapping, neuroglial cells. Double-positive cells were isolated by fluorescence-activated cell sorting (FACS) and analyzed by RNA sequencing. To reveal defining patterns of mural cell transcripts, we compared the RNA sequencing data with data from four previously published studies. The meta-analysis provided a conservative catalogue of 260 brain mural cell-enriched gene transcripts. We validated pericyte-specific expression of two novel markers, vitronectin (Vtn) and interferon-induced transmembrane protein 1 (Ifitm1), using fluorescent in situ hybridization and immunohistochemistry. We further analyzed signaling pathways and interaction networks of the pericyte-enriched genes in silico. This work provides novel insight into the molecular composition of brain mural cells. The reported gene catalogue facilitates identification of brain pericytes by providing numerous new candidate marker genes and is a rich source for new hypotheses for future studies of brain mural cell physiology and pathophysiology.
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- Kusumbe, Anjali P., et al.
(author)
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Age-dependent modulation of vascular niches for haematopoietic stem cells
- 2016
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In: Nature. - : Springer Science and Business Media LLC. - 0028-0836 .- 1476-4687. ; 532:7599, s. 380-
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Journal article (peer-reviewed)abstract
- Blood vessels define local microenvironments in the skeletal system, play crucial roles in osteogenesis and provide niches for haematopoietic stem cells(1-6). The properties of nicheforming vessels and their changes in the ageing organism remain incompletely understood. Here we show that Notch signalling in endothelial cells leads to the expansion of haematopoietic stem cell niches in bone, which involves increases in CD31-positive capillaries and platelet-derived growth factor receptor-beta (PDGFR beta)-positive perivascular cells, arteriole formation and elevated levels of cellular stem cell factor. Although endothelial hypoxia-inducible factor signalling promotes some of these changes, it fails to enhance vascular niche function because of a lack of arterialization and expansion of PDGFR beta-positive cells. In ageing mice, niche-forming vessels in the skeletal system are strongly reduced but can be restored by activation of endothelial Notch signalling. These findings indicate that vascular niches for haematopoietic stem cells are part of complex, age-dependent microenvironments involving multiple cell populations and vessel subtypes.
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- Vanlandewijck, Michael, et al.
(author)
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Functional Characterization of Germline Mutations in PDGFB and PDGFRB in Primary Familial Brain Calcification
- 2015
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In: PLOS ONE. - : Public Library of Science (PLoS). - 1932-6203. ; 10:11
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Journal article (peer-reviewed)abstract
- Primary Familial Brain Calcification (PFBC), a neurodegenerative disease characterized by progressive pericapillary calcifications, has recently been linked to heterozygous mutations in PDGFB and PDGFRB genes. Here, we functionally analyzed several of these mutations in vitro. All six analyzed PDGFB mutations led to complete loss of PDGF-B function either through abolished protein synthesis or through defective binding and/or stimulation of PDGF-R beta. The three analyzed PDGFRB mutations had more diverse consequences. Whereas PDGF-R beta autophosphorylation was almost totally abolished in the PDGFRB L658P mutation, the two sporadic PDGFRB mutations R987W and E1071V caused reductions in protein levels and specific changes in the intensity and kinetics of PLC. activation, respectively. Since at least some of the PDGFB mutations were predicted to act through haploinsufficiency, we explored the consequences of reduced Pdgfb or Pdgfrb transcript and protein levels in mice. Heterozygous Pdgfb or Pdgfrb knockouts, as well as double Pdgfb(+/-); Pdgfrb(+/-) mice did not develop brain calcification, nor did Pdgfrb(redeye/redeye) mice, which show a 90% reduction of PDGFR beta protein levels. In contrast, Pdgfb(ret/ret) mice, which have altered tissue distribution of PDGF-B protein due to loss of a proteoglycan binding motif, developed brain calcifications. We also determined pericyte coverage in calcification-prone and non-calcification-prone brain regions in Pdgfb(ret/ret) mice. Surprisingly and contrary to our hypothesis, we found that the calcification-prone brain regions in Pdgfb(ret/ret) mice model had a higher pericyte coverage and a more intact blood-brain barrier (BBB) compared to non-calcification-prone brain regions. While our findings provide clear evidence that loss-of-function mutations in PDGFB or PDGFRB cause PFBC, they also demonstrate species differences in the threshold levels of PDGF-B/PDGF-R beta signaling that protect against small-vessel calcification in the brain. They further implicate region-specific susceptibility factor(s) in PFBC pathogenesis that are distinct from pericyte and BBB deficiency.
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