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Proceedings Paper

In vivo FCS measurements of ligand diffusion in intact tissues
Author(s): Zifu Wang; Oana Marcu; Michael W. Berns; J. Lawrence Marsh
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Paper Abstract

Tissue patterns appear to be specified by gradients of morphogens. Although it has been established that morphogens are indeed distributed in gradients (morphogenetic gradients), how these gradients arise is not well understood. Two main types of mechanisms have been proposed: (1) diffusion-based, and (2) transcytosis; a third "bucket-brigade" mechanism has also been proposed. The diffusion model is based on the assumption that a morphogen diffuses from a region of origin to form the gradient. The other model proposes that morphogens instead are taken up by one cell and transit that cell to be released on the other side. A third model proposes a “bucket brigade” mechanism in which receptor-bound morphogens on one cell move by being handed off to receptors on an adjacent cell. To provide insight into the mechanism of the formation of the morphogen gradients, we conducted fluorescence correlation spectroscopy (FCS) measurements of morphogen Dpp-EGFP fusion protein in intact Drosophila imaginal disks with two-photon excitation at 850 nm. The FCS results are analyzed with a two-species model. The first species can be attributed to Dpp-EGFP in Brownian motion, while the second species could result from either a large complex involving Dpp-EGFP formed through biochemical reactions, or from anomalous diffusion of Dpp, presumably due to its transport along the cell membranes. Our studies demonstrate for the first time that FCS is capable of investigating molecular dynamics in intact tissues.

Paper Details

Date Published: 21 June 2004
PDF: 7 pages
Proc. SPIE 5323, Multiphoton Microscopy in the Biomedical Sciences IV, (21 June 2004); doi: 10.1117/12.528642
Show Author Affiliations
Zifu Wang, Developmental Biology Ctr./Univ. of California/Irvine (United States)
Oana Marcu, Developmental Biology Ctr./Univ. of California/Irvine (United States)
Michael W. Berns, Beckman Laser Institute/Univ. of California/Irvine (United States)
J. Lawrence Marsh, Developmental Biology Ctr./Univ. of California/Irvine (United States)


Published in SPIE Proceedings Vol. 5323:
Multiphoton Microscopy in the Biomedical Sciences IV
Ammasi Periasamy; Peter T. C. So, Editor(s)

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