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      Simultaneous imaging of GFP, CFP and collagen in tumors in vivo using multiphoton microscopy

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          Abstract

          Background

          The development of multiphoton laser scanning microscopy has greatly facilitated the imaging of living tissues. However, the use of genetically encoded fluorescent proteins to distinguish different cell types in living animals has not been described at single cell resolution using multiphoton microscopy.

          Results

          Here we describe a method for the simultaneous imaging, by multiphoton microscopy, of Green Fluorescent Protein, Cyan Fluorescent Protein and collagen in vivo in living tumors. This novel method enables: 1) the simultaneous visualization of overall cell shape and sub-cellular structures such as the plasma membrane or proteins of interest in cells inside living animals, 2) direct comparison of the behavior of single cells from different cell lines in the same microenvironment in vivo.

          Conclusion

          Using this multi-fluor, multiphoton technique, we demonstrate that motility and metastatic differences between carcinoma cells of differing metastatic potential can be imaged in the same animal simultaneously at sub-cellular resolution.

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          Most cited references28

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          Interpreting second-harmonic generation images of collagen I fibrils.

          Fibrillar collagen, being highly noncentrosymmetric, possesses a tremendous nonlinear susceptibility. As a result, second-harmonic generation (SHG) microscopy of collagen produces extremely bright and robust signals, providing an invaluable tool for imaging tissue structure with submicron resolution. Here we discuss fundamental principles governing SHG phase matching with the tightly focusing optics used in microscopy. Their application to collagen imaging yields several biophysical features characteristic of native collagen structure: SHG radiates from the shell of a collagen fibril, rather than from its bulk. This SHG shell may correspond to the supporting element of the fibril. Physiologically relevant changes in solution ionic strength alter the ratio of forward-to-backward propagating SHG, implying a resulting change in the SHG shell thickness. Fibrillogenesis can be resolved in immature tissue by directly imaging backward-propagating SHG. Such findings are crucial to the design and development of forthcoming diagnostic and research tools.
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            Differential Localization of Rho Gtpases in Live Cells

            Determinants of membrane targeting of Rho proteins were investigated in live cells with green fluorescent fusion proteins expressed with or without Rho-guanine nucleotide dissociation inhibitor (GDI)α. The hypervariable region determined to which membrane compartment each protein was targeted. Targeting was regulated by binding to RhoGDIα in the case of RhoA, Rac1, Rac2, and Cdc42hs but not RhoB or TC10. Although RhoB localized to the plasma membrane (PM), Golgi, and motile peri-Golgi vesicles, TC10 localized to PMs and endosomes. Inhibition of palmitoylation mislocalized H-Ras, RhoB, and TC10 to the endoplasmic reticulum. Although overexpressed Cdc42hs and Rac2 were observed predominantly on endomembrane, Rac1 was predominantly at the PM. RhoA was cytosolic even when expressed at levels in vast excess of RhoGDIα. Oncogenic Dbl stimulated translocation of green fluorescent protein (GFP)-Rac1, GFP-Cdc42hs, and GFP-RhoA to lamellipodia. RhoGDI binding to GFP-Cdc42hs was not affected by substituting farnesylation for geranylgeranylation. A palmitoylation site inserted into RhoA blocked RhoGDIα binding. Mutations that render RhoA, Cdc42hs, or Rac1, either constitutively active or dominant negative abrogated binding to RhoGDIα and redirected expression to both PMs and internal membranes. Thus, despite the common essential feature of the CAAX (prenylation, AAX tripeptide proteolysis, and carboxyl methylation) motif, the subcellular localizations of Rho GTPases, like their functions, are diverse and dynamic.
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              Identification and testing of a gene expression signature of invasive carcinoma cells within primary mammary tumors.

              We subjected cells collected using an in vivo invasion assay to cDNA microarray analysis to identify the gene expression profile of invasive carcinoma cells in primary mammary tumors. Expression of genes involved in cell division, survival, and cell motility were most dramatically changed in invasive cells indicating a population that is neither dividing nor apoptotic but intensely motile. In particular, the genes coding for the minimum motility machine that regulates beta-actin polymerization at the leading edge and, therefore, the motility and chemotaxis of carcinoma cells, were dramatically up-regulated. However, ZBP1, which restricts the localization of beta-actin, the substrate for the minimum motility machine, was down-regulated. This pattern of expression implicated ZBP1 as a suppressor of invasion. Reexpression of ZBP1 in metastatic cells with otherwise low levels of ZBP1 reestablished normal patterns of beta-actin mRNA targeting and suppressed chemotaxis and invasion in primary tumors. ZBP1 reexpression also inhibited metastasis from tumors. These experiments support the involvement in metastasis of the pathways identified in invasive cells, which are regulated by ZBP1.
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                Author and article information

                Journal
                BMC Biotechnol
                BMC Biotechnology
                BioMed Central (London )
                1472-6750
                2005
                23 May 2005
                : 5
                : 14
                Affiliations
                [1 ]Tumour Cell Biology Laboratory, Cancer Research UK London Research Institute, London WC2A 3PX, UK
                [2 ]Department of Anatomy and Structural Biology, Albert Einstein College of Medicine, 1300 Morris Park Avenue, Bronx, NY 10461, USA
                [3 ]Department of Biology, Massachusetts Institute of Technology, 77 Massachusetts Avenue, Cambridge, MA 02139, USA
                [4 ]Analytical Imaging Facility, Albert Einstein College of Medicine, 1300 Morris Park Avenue, Bronx, NY 10461, USA
                Article
                1472-6750-5-14
                10.1186/1472-6750-5-14
                1159039
                15910685
                aaad6fa7-dbe3-4e36-a8b3-050508f0ca59
                Copyright © 2005 Sahai et al; licensee BioMed Central Ltd.

                This is an Open Access article distributed under the terms of the Creative Commons Attribution License ( http://creativecommons.org/licenses/by/2.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

                History
                : 18 February 2005
                : 23 May 2005
                Categories
                Methodology Article

                Biotechnology
                Biotechnology

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