ABSTRACT
During invasion, cells breach basement membrane (BM) barriers with actin-rich protrusions. It remains unclear, however, whether actin polymerization applies pushing forces to help break through BM, or whether actin filaments play a passive role as scaffolding for targeting invasive machinery. Here, using the developmental event of anchor cell (AC) invasion in Caenorhabditis elegans, we observe that the AC deforms the BM and underlying tissue just before invasion, exerting forces in the tens of nanonewtons range. Deformation is driven by actin polymerization nucleated by the Arp2/3 complex and its activators, whereas formins and cross-linkers are dispensable. Delays in invasion upon actin regulator loss are not caused by defects in AC polarity, trafficking, or secretion, as appropriate markers are correctly localized in the AC even when actin is reduced and invasion is disrupted. Overall force production emerges from this study as one of the main tools that invading cells use to promote BM disruption in C. elegans.
Subject(s)
Actin-Related Protein 2-3 Complex/metabolism , Actins/metabolism , Basement Membrane/metabolism , Caenorhabditis elegans/metabolism , Gene Expression Regulation, Developmental , Mechanotransduction, Cellular , Actin-Related Protein 2-3 Complex/genetics , Actins/genetics , Animals , Basement Membrane/cytology , Biomechanical Phenomena , Caenorhabditis elegans/cytology , Caenorhabditis elegans/genetics , Caenorhabditis elegans/growth & development , Caenorhabditis elegans Proteins/genetics , Caenorhabditis elegans Proteins/metabolism , Cell Movement , Eukaryotic Cells/cytology , Eukaryotic Cells/metabolism , Fetal Proteins/genetics , Fetal Proteins/metabolism , Formins , Genes, Reporter , Green Fluorescent Proteins/genetics , Green Fluorescent Proteins/metabolism , Laminin/genetics , Laminin/metabolism , Luminescent Proteins/genetics , Luminescent Proteins/metabolism , Microfilament Proteins/genetics , Microfilament Proteins/metabolism , Morphogenesis/genetics , Nuclear Proteins/genetics , Nuclear Proteins/metabolism , Polymerization , Red Fluorescent ProteinABSTRACT
In recent years, the analysis of circulating cell-free DNA (cfDNA) containing tumor-derived DNA has emerged as a noninvasive means for cancer monitoring and personalized medicine. However, the isolation of cfDNA from peripheral blood has remained a challenge due to the low abundance and high fragmentation of these molecules. Here, we present a dynamic Magnetic ExTRactiOn (METRO) protocol using microfluidic fluidized bed technology to isolate circulating cfDNA from raw biological materials such as undiluted serum. This protocol maximizes the surface area for DNA binding within the chip in order to capture short DNA fragments. It uses only a few µL of sample and reagents. The protocol can be automated, and it is fully compatible with sensitive DNA amplification methods such as droplet-based digital PCR (ddPCR).
Subject(s)
Cell-Free Nucleic Acids , Lab-On-A-Chip Devices , Humans , Cell-Free Nucleic Acids/isolation & purification , Cell-Free Nucleic Acids/blood , Cell-Free Nucleic Acids/genetics , Polymerase Chain Reaction/methods , Microfluidic Analytical Techniques/methods , Microfluidic Analytical Techniques/instrumentation , Magnetics/methods , Neoplasms/blood , Neoplasms/genetics , Neoplasms/diagnosisABSTRACT
Rac1 is a small RhoGTPase switch that orchestrates actin branching in space and time and protrusion/retraction cycles of the lamellipodia at the cell front during mesenchymal migration. Biosensor imaging has revealed a graded concentration of active GTP-loaded Rac1 in protruding regions of the cell. Here, using single-molecule imaging and super-resolution microscopy, we show an additional supramolecular organization of Rac1. We find that Rac1 partitions and is immobilized into nanoclusters of 50-100 molecules each. These nanoclusters assemble because of the interaction of the polybasic tail of Rac1 with the phosphoinositide lipids PIP2 and PIP3. The additional interactions with GEFs and possibly GAPs, downstream effectors, and other partners are responsible for an enrichment of Rac1 nanoclusters in protruding regions of the cell. Our results show that subcellular patterns of Rac1 activity are supported by gradients of signaling nanodomains of heterogeneous molecular composition, which presumably act as discrete signaling platforms.