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Phong Tran, Ph.D.

Phong Tran, Ph.D.

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Associate Professor of Cell and Developmental Biology
Department: Cell and Developmental Biology

Contact information
421 Curie Boulevard
Philadelphia, PA 19104-5058
Office: 215-746-2755
Fax: 215-898-9871
B.A. (Biophysics)
University of California – Berkeley, 1991.
Ph.D. (Cell Biology)
University of North Carolina – Chapel Hill, 1998.
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Description of Research Expertise

Research Interests
The cytoskeleton and cellular pattern formation.

Key words: microtubule, microscopy, S. pombe, cell polarity, mitosis, microfabrication, microfluidics

Description of Research
Our lab is interested in understanding how positional information is generated within the cell. We use high resolution optical imaging and analysis techniques, the green fluorescent protein GFP and its genetically encoded variants as non-invasive fluorescent biosensors, and the fission yeast Schizosaccharomyces pombe – with its well-defined shape, size, and genetic tractability – as ideal tools for studying cellular pattern formation.

Figure 1.

Our previous studies in the fission yeast have established that the microtubule cytoskeleton defines a spatial map of positional information for the cell (Fig. 1). We aim to test various aspects of this model, particularly:

A model for the establishment of positional information. In wild-type cells, iMTOCs arrange microtubules in bilaterally symmetric bundles such that a balance of pushing forces from the microtubule plus ends positions the nucleus in the cell center. The microtubule plus ends, with regulated organization and kinetics, can mark sites of polarized cell growth, at the cell tips. The microtubule cytoskeleton thus acts as a dynamic spatial regulator, continually monitoring and defining sub-cellular domains.

1. Identify the molecular components of the microtubule organizing centers.

The iMTOCs are novel microtubule-organizing-centers in fission yeast. We envision that components of the iMTOCs include microtubule bundling and stabilizing factors and perhaps nuclear attachment factors (Fig. 2). Previously we have characterized rsp1, the only known protein component of the iMTOC. We have identified rsp2, a mutant whose phenotype resemble those of rsp1, and will undertake molecular characterization to determine their roles in iMTOC organization and function. rsp2 mutant cells have abnormally short microtubules, leading to nuclear positioning defects.

Figure 2.

2. Define the interactions of known microtubule-associated-proteins with the microtubule ends and the roles of these proteins in bringing about proper nuclear positioning and cellular pattern.

We have identified rnd1 and rnd2, mutants with round-cell phenotypes (Fig. 3). Characterization of rnd1 and rnd2 is underway to define the molecular pathway of pattern formation. Results of a random insertional mutagenesis screen for morphologically round mutants. Individual fission yeast colonies were viewed and selected manually under the microscope.

Figure 3.

3. Develop and apply advanced optical imaging and analysis methods to the yeast system.

High resolution optical imaging and analysis techniques, use of the green fluorescent protein and its variants as non-invasive fluorescent biosensors, and the model organism Schizosaccharomyces pombe with its well-defined shape, size, and genetic tractability constitute ideal, proven tools for studying cellular spatial organization and regulation.

Selected Publications

Inoué S, Shimomura O, Goda M, Shribak M, and Tran PT: Fluorescence polarization of green fluorescent protein. Proc. Nat. Acad. Sci. (USA) 99: 4272-4277, 2002.

Tran PT and Chang F: Transmitted light fluorescence microscopy revisited. Biol. Bull. 201: 235-236, 2001.

Cassimeris L, Gard D, Tran PT, and Erickson HP: XMAP215 is a long thin molecule, which does not increase microtubule stiffness. J. Cell Sci. 114: 3025-3033, 2001.

Tran PT, Marsh L, Doye V, Inoué S, and Chang F: A mechanism for nuclear positioning in fission yeast based upon microtubule pushing. J. Cell Biol. 153: 397-411, 2001.

Tran PT, Doye V, Chang F, Inoue S: Microtubule-dependent nuclear positioning and nuclear-dependent septum positioning in the fission yeast Schizosaccharomyces pombe (* Cover Picture). Biol. Bull. 199: 205-206, 2000 Notes: Cover Picture of Issue.

Danuzer G, Tran PT, and Salmon ED: Tracking DIC diffraction line images with nanometer sensitivity. J. Microscopy 198: 34-53, 2000.

Tran PT, Maddox P, Chang F, and Inoue S: Dynamic confocal imaging of interphase and mitotic microtubules in the fission yeast, S. pombe. Biol. Bull. 197: 262-263, 1999.

Oldenbourg R, Salmon ED, and Tran PT: Birefringence of single and bundled microtubules. Biophys. J. 74: 645-654, 1998.

Salmon ED and Tran PT: High-resolution video-enhanced differential interference contrast light microscopy [Methods] Meth. Cell. Biol. 56: 153-184, 1998.

Inoue S, Tran PT, and Burgos MH: Photodynamic effect of 488-nm light on Eosin-B-stained Spisula sperm. Biol. Bull. 193: 225-226, 1997.

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Last updated: 06/09/2009
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