Abstract 362: Fibronectin facilitates extracellular matrix assembly and vascular morphogenesis .

The assembly of an organism requires the interaction between different layers of cells, in many cases via an extracellular matrix. In the developing Drosophila larva, muscles attach in an integrin-dependent manner to the epidermis, via a specialized extracellular matrix called tendon matrix. Tiggrin, a tendon matrix integrin ligand, is primarily synthesized by cells distant to the muscle attachment sites, yet it accumulates specifically at these sites. Previous work has shown that the PS integrins are not required for tiggrin localization, suggesting that there is redundancy among tiggrin receptors. We have examined this by testing whether the PS2 integrin can recruit tiggrin to ectopic locations within the Drosophila embryo. We found that neither the wild type nor modified forms of the PS2 integrin, which have higher affinity for tiggrin, can recruit tiggrin to new cellular contexts. Next, we genetically manipulated the fate of the muscles and the epidermal muscle attachment cells, which demonstrated that muscles have the primary role in recruiting tiggrin to the tendon matrix and that cell-cell contact is necessary for this recruitment. Thus we propose that the inherent polarity of the muscle cells leads to a molecular specialization of their ends, and interactions between the ends produces an integrin-independent tiggrin receptor. Thus, interaction between cells generates an extracellular environment capable of nucleating extracellular matrix assembly.

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Control of extracellular matrix assembly by syndecan-2 proteoglycan

Journal of Cell Science ◽

10.1242/jcs.113.3.493 ◽

2000 ◽

Vol 113 (3) ◽

pp. 493-506 ◽

Cited By ~ 10

Author(s):

C.M. Klass ◽

J.R. Couchman ◽

A. Woods

Keyword(s):

Extracellular Matrix ◽

Chinese Hamster ◽

Surface Expression ◽

Metabolic Labeling ◽

Sulfate Proteoglycan ◽

S2 Cells ◽

Matrix Assembly ◽

The Matrix ◽

Beta1 Integrin ◽

Assembly Defect

Extracellular matrix (ECM) deposition and organization is maintained by transmembrane signaling and integrins play major roles. We now show that a second transmembrane component, syndecan-2 heparan sulfate proteoglycan, is pivotal in matrix assembly. Chinese Hamster Ovary (CHO) cells were stably transfected with full length (S2) or truncated syndecan-2 lacking the C-terminal 14 amino acids of the cytoplasmic domain (S2deltaS). No differences in the amount of matrix assembly were noted with S2 cells, but those expressing S2deltaS could not assemble laminin or fibronectin into a fibrillar matrix. The loss of matrix formation was not caused by a failure to synthesize or externalize ECM components as determined by metabolic labeling or due to differences in surface expression of alpha5 or beta1 integrin. The matrix assembly defect was at the cell surface, since S2deltaS cells also lost the ability to rearrange laminin or fibronectin substrates into fibrils and to bind exogenous fibronectin. Transfection of activated alphaIIbalphaLdeltabeta3 integrin into alpha(5)-deficient CHO B2 cells resulted in reestablishment of the previously lost fibronectin matrix. However, cotransfection of this cell line with S2deltaS could override the presence of activated integrins. These results suggest a regulatory role for syndecan-2 in matrix assembly, along with previously suggested roles for activated integrins.

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Establishment of substratum polarity in the blastocoel roof of the Xenopus embryo

Development ◽

10.1242/dev.126.9.1975 ◽

1999 ◽

Vol 126 (9) ◽

pp. 1975-1984 ◽

Cited By ~ 3

Author(s):

M. Nagel ◽

R. Winklbauer

Keyword(s):

Extracellular Matrix ◽

Cell Migration ◽

Signaling Pathways ◽

Fibril Formation ◽

Fgf Signaling ◽

Matrix Assembly ◽

Mesoderm Cell ◽

Guidance Cues ◽

Mesoderm Formation ◽

Fibronectin Fibrils

The fibronectin fibril matrix on the blastocoel roof of the Xenopus gastrula contains guidance cues that determine the direction of mesoderm cell migration. The underlying guidance-related polarity of the blastocoel roof is established in the late blastula under the influence of an instructive signal from the vegetal half of the embryo, in particular from the mesoderm. Formation of an oriented substratum depends on functional activin and FGF signaling pathways in the blastocoel roof. Besides being involved in tissue polarization, activin and FGF also affect fibronectin matrix assembly. Activin treatment of the blastocoel roof inhibits fibril formation, whereas FGF modulates the structure of the fibril network. The presence of intact fibronectin fibrils is permissive for directional mesoderm migration on the blastocoel roof extracellular matrix.

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Hypoxia and matrix viscoelasticity sequentially regulate endothelial progenitor cluster-based vasculogenesis

Science Advances ◽

10.1126/sciadv.aau7518 ◽

2019 ◽

Vol 5 (3) ◽

pp. eaau7518 ◽

Cited By ~ 14

Author(s):

Michael R. Blatchley ◽

Franklyn Hall ◽

Songnan Wang ◽

Hawley C. Pruitt ◽

Sharon Gerecht

Keyword(s):

Reactive Oxygen Species ◽

Extracellular Matrix ◽

Network Formation ◽

Underlying Mechanism ◽

Oxygen Species ◽

Endothelial Progenitor ◽

Vascular Morphogenesis ◽

The Matrix ◽

Surrounding Extracellular Matrix

Vascular morphogenesis is the formation of endothelial lumenized networks. Cluster-based vasculogenesis of endothelial progenitor cells (EPCs) has been observed in animal models, but the underlying mechanism is unknown. Here, using O2-controllabe hydrogels, we unveil the mechanism by which hypoxia, co-jointly with matrix viscoelasticity, induces EPC vasculogenesis. When EPCs are subjected to a 3D hypoxic gradient ranging from <2 to 5%, they rapidly produce reactive oxygen species that up-regulate proteases, most notably MMP-1, which degrade the surrounding extracellular matrix. EPC clusters form and expand as the matrix degrades. Cell-cell interactions, including those mediated by VE-cadherin, integrin-β2, and ICAM-1, stabilize the clusters. Subsequently, EPC sprouting into the stiffer, intact matrix leads to vascular network formation. In vivo examination further corroborated hypoxia-driven clustering of EPCs. Overall, this is the first description of how hypoxia mediates cluster-based vasculogenesis, advancing our understanding toward regulating vascular development as well as postnatal vasculogenesis in regeneration and tumorigenesis.

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