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Stephen Doxsey, Ph.D.

Academic Role: Professor

Faculty Appointment(s) In:
   Program in Molecular Medicine

Joint Faculty In:
   Biochemistry and Molecular Pharmacology

Other Affiliation(s):
   Cell Biology
   Cell Dynamics Group
   Interdisciplinary Graduate Program

Regulation of Mitotic Spindle Assembly

Microtubules are required for such fundamental cellular processes as cell division, embryogenesis, cell motility and organelle translocation. In all animal cells, the microtubule cytoskeleton arises from the centrosome, an organelle with the ability to nucleate microtubules.

This laboratory is interested in understanding how the centrosome organizes microtubule arrays such as the mitotic spindle. We have cloned and characterized pericentrin, a highly conserved centrosome protein essential for cell division and microtubule organization. Pericentrin forms a large complex with gamma tubulin and other proteins involved in microtubule nucleation. Expression of mutated forms of pericentrin in cells induces the formation of 'ectopic centrosomes' that nucleate microtubules. Current work involves expression of chimeras of pericentrin and green fluorescent protein to monitor centrosome dynamics and function in living cells. In collaboration with the Biomedical Imaging Group, who developed new superresolution immunofluorescence technology, we discovered that centrosomes are comprised of a novel lattice structure (see Figure A). The mechanism and regulation of centrosome assembly is being investigated using in vitro reconstitution systems and in vivo systems developed in our laboratory. Centrosome assembly in mammalian cells is microtubule-dependent and mediated by the molecular motor, dynein. We are characterizing other highly conserved, novel centrosome proteins identified with serum from patients with the autoimmune disease, scleroderma. Finally, we recently discovered that pericentrin is overexpressed in tumors and that tumor cells have abnormal centrosomes, suggesting a possible role of pericentrin in tumorigenesis.

Figure

A. Immunofluorescence image of microtubules (red) grown from a centrosome (yellow). The centrosome was stained with antibodies to pericentrin, a highly conserved and essential centrosome protein. The novel centrosome lattice revealed in this image was discovered using imaging technology recently developed by Dr. Fred Fay and coworkers here at UMass.

Recent Publications

Doxsey, S.J. Re-evaluating centrosome function.  Nature Rev., Molec Biol. 2, 688-699, 2001.

Pihan, G., Zhou, Y., Wallace, J., Zhou, Y. and Doxsey, S.  Centrosome abnormalities and genetic instability occur together in precancerous lesions.  Cancer Res., 63, 1398-1404, 2003.

Gromley, A., Jurczyk, A., Sillibourne, J., Halilovic, E., Mogenson, M., Groisman, I., Blomberg, M., and Doxsey, S.  A novel human protein of the maternal centriole is required for the final stages of cytokinesis and entry into S phase.  J. Cell Biol, 161, 535-545, 2003.

Pihan, G. and Doxsey, S.  Mutations and aneuploidy:  Co-conspirators in cancer?  Cancer Cell 4, 89-94, 2003.

Chen, D., Purohit, A., Halilovic, E., Doxsey, S., Newton, A.  Protein kinase C anchoring at the centrosome controls cytokinesis.  J. Biol. Chem., 279, 4829, 2004.  (cover photo)

Jurczyk, A., Gromley, A., Redick, S., San Augustin, J., Witman, G., Pazour, G., Peters, J.M. and Doxsey, S.  Pericentrin is required for primary cilia assembly and anchoring intraflagellar transport proteins at basal bodies.  J. Cell Biol. 166,637-643, 2004.

Gavanescu, I., Pihan, G., Halilovic, E., Szomolanyi-Tsuda, E., Welsh, R., and Doxsey, S.  Mycoplasma infection induces a scleroderma-like centrosome autoantibody response in mice.  Clin. Exp. Immun. 137, 288-297, 2004.

Doxsey, S., Zimmerman, W., Mikule, K.  Centrosome control of the cell cycle.  Trends Cell Biol. 15, 303-311, 2005.

Gromley A, Yeaman C, Rosa J, Redick S, Chen C, Mirabelle, S, Guha, M and Doxsey S. Centriolin-anchoring of exocyst and SNARE complexes at the midbody is required for secretory vesicle-mediated abscission. Cell 123, 75-87, 2005.

Doxsey S, Zimmerman S, Mikule K.  Centrosome control of the cell cycle.  Trends Cell Biol. 15, 303-311, 2005.

Doxsey S, McCollum D, Theurkauf, W.  Centrosomes in cellular regulation.  Ann Rev Cell Dev Biol, 21, 411-434, 2005.

Doxsey, S. Molecular links between centrosome and midbody. Molecular Cell, 20, 170-172, 2005.

Mikule K, Delaval B, Kaldis P, Jurczyk A, Hergert P, Doxsey S.  Loss of centrosome integrity induces p38-p53-p21-dependent G1-S arrest.  Nat Cell Biol. Feb 9(2): 160-70, 2007.

Potential Rotation Projects:

Project #1: Centrosomes, chromosome segregation and cancer. We have shown that the assembly of centrosomes is essential for spindle function (Zimmerman et al., 1999, 2000; Doxsey, 2001). We recently discovered that centrosomes assemble by an unexpected mechanism involving the molecular motor cytoplasmic dynein (Young et al, 2000; Tynan et al., 2000). This mechanism is mediated by a direct interaction between the essential centrosome protein pericentrin (Doxsey et al., 1994; Dictenberg et al., 1998) and the dynein light intermediate chain (Purohit et al., 1999; Tynana et al., 2000). Moreover, pericentrin interacts with many proteins including the g tubulin complex, which nucleates microtubules (Dictenberg et al., 1998; Diviani et al., 2000). Centrosome assembly is disrupted in human cancer--nearly all malignant tumors have aberrant centrosomes (Pihan et al., 1998, Doxsey, 1999). To our surprise, most tumor cells overexpress pericentrin and artificial overexpression of pericentrin in normal cells induces a cancer-like phenotype (Purohit et al., 1999; Pihan et al., 2000, 2001). Projects:

1. Determine how centrosome assembly is regulated.
2. Determine the role of the pericentrin-dynein interaction in spindle organization.
3. Test how increased pericentrin levels and centrosome defects contribute to cancer.
4. Identify novel pericentrin-binding proteins.
5. Determine how pericentrin levels and functions are regulated.
6. Determine how pericentrin binds and transports g tubulin complexes to centrosomes.

Project #2: Mechanism of autoantibody production in autoimmunity. Centrosomes are targeted by autoantibodies in the human autoimmune disease scleroderma (Gavanescu et al., 1999), although the mechanism is unknown. We recently discovered that centrosome autoantibodies can be induced an infectious agent (Gavanescu et al., in prep). PCR analysis demonstrated ectopic localization of this organism to skin lesions of scleroderma patients but not controls. These results suggest that this agent contributes to autoantibody development, disease pathogenesis and immune dysfunction in scleroderma patients. Projects:

1. Determine the mechanism of autoantibody production in mice mutant for immune components.
2. Test whether centrosome autoreactivity precedes other autoantibodies (anti-nuclear).
3. Determine if this agent is present in other autoimmune diseases.
4. Determine if the pathological symptoms of scleroderma are alleviated following treatment of the agent.

Laboratory Personnel

Post-Doctoral Fellows: Desiree Baron, Benedicte Delaval, Sivaram Mylavarapu, Anastassiia Vertii, Guoqiang Zheng

Technician:  Sambra Redick

Graduate Students: Seemin Ahmed, Alison Bright, Chun-Ting Chen, Tse-Chun Kuo, Cara Weismann

Academic Background

Stephen Doxsey received his BS from the University of Connecticut in 1977 and his PhD in Cell Biology from Yale University in 1987. He was awarded Anna Fuller and Damon Runyon Fellowships during his postdoctoral training in Dr. Marc Kirschner's laboratory at the University of California at San Francisco. Dr. Doxsey joined the faculty at the University of Massachusetts Medical School in the Program in Molecular Medicine in 1993.

Office: Biotech II-Suite 210
Phone: 508-856-1613
E-mail: Stephen.Doxsey@umassmed.edu
Keywords: Cancer Biology, Cell Biology, Biochemistry

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