Title: Assistant Professor
Area of Study: Genetics, Cell Biology
Office: Science & Technology Building, 518
Address: Department of Biology
East Carolina University
Greenville, NC 27858
B.S., University of Utah, 1996
Ph.D., Cornell University, 2002
Using the model organism Drosophila melanogaster we study the intersection of DNA replication and heterochromatic silencing. DNA replication is an essential process that must be carried out with high fidelity. Dire consequences result when this process fails to faithfully duplicate DNA both with respect to sequence and at the right time during the cell cycle.
The suite of proteins involved in DNA replication do not operate on a naked DNA substrate but rather must perform in the context of the higher order structure of chromatin. Re-establishment of chromatin states during or right after DNA replication is critical for the organism. High fidelity of this process ensures that the transcriptional states of numerous genes are maintained. In addition the modulation of these states can contribute to the differentiation and development of tissues within the body.
What is becoming increasingly apparent is the processes of DNA replication and establishment of chromatin structure are linked. Moreover this linkage is likely the result of multiple functions for DNA replication proteins. Proteins such as the Origin recognition complex (ORC), mini-chromosome maintenance proteins (MCMs), and members of the DNA elongation machinery have all been implicated in the establishment of chromatin states during and after DNA replication.
In our lab we explore these linkages between DNA replication and chromatin through the use of a wide variety of techniques. We employ classical genetic approaches to understand the impact of mutations in selected genes on the establishment of heterochromatin (a repressive tightly packaged form of chromatin), DNA replication, and development. We seek to understand the phenotypes observed through the use of transgenic flies and high resolution microscopy. In addition to classical genetic approaches we seek to understand the function of selected proteins through identification of interacting proteins. To accomplish this we use two-hybrid analysis, immuno-precipitation, and affinity chromatography techniques.
Motivated students looking for research experience are encouraged to contact me to discuss the possibility of contributing to our research. If you are looking for advanced degrees East Carolina University and the Department of Biology have a Master of Science degree program and an Interdisciplinary Ph.D. degree program (IDPBS). I am looking for those students (both Undergrad and Grad) who are eager to work on a dynamic research topic and who are motivated to tackle the challenges and rewards of research. Please contact me with any questions.
Drosophila Psf2 has a Role in Chromosome Condensation. Chmielewski JP, Henderson L, Christensen TW, Chromosoma , 2012 121(6) 585-596
Multiple functions for Drosophila Mcm10 suggested through analysis of two Mcm10 mutant alleles. Apger J, Reubens M, Henderson L, Gouge CA, Ilic N, Zhou HH, Christensen TW. Genetics. 2010 Aug;185(4):1151-65.
Novel Method for Determining Chromosome Compaction and DNA Content of Salivary Gland Nuclei in Drosophila. Chmielewski JP, Christensen TW, Drosophila Information Services, 2011, 94
Drosophila Ctf4 is essential for efficient DNA replication and normal cell cycle progression. Gosnell JA & Christensen TW. BMC Molecular Biology, 2011, 12:13
Drosophila Sld5 is essential for normal cell cycle progression and maintenance of genomic integrity. Gouge CA & Christensen TW. Biochemical and Biophysical Research Communications, 2010 Sep 10;400(1):145-50
Detection of S Phase Cells in Multiple Drosophila Tissues Utilizing the EdU Labeling Technique. Gouge CA & Christensen TW. Drosophila Information Service, 2010, 93
Effective Terminal Sterilization Using Supercritical Carbon Dioxide White, A., Burns, D. Christensen, T.W. J Biotech. 2006 Jun 10;123(4):504-15
Drosophila Mcm10 interacts with members of the pre-replication complex and is required for proper chromosome condensation. Christensen, T.W. and Tye, B.K.(2003) Mol Biol Cell. 14: 2206-2215
Mcm1 binds replication origins. Chang, V., Fitch, M.J. Donato, J.J., Christensen, T.W., Merchant, A.M. and Tye, B.K. (2003) J Biol Chem. 278: 6093-6100.
Mcm10 and the MCM2 7 complex interact to initiate DNA synthesis and to release replication factors from origins. Homesley L, Lei M, Kawasaki Y, Sawyer S, Christensen T, Tye BK Genes Dev 2000 Apr 15 14:8 913 26
The FILAMENTOUS FLOWER gene is required for flower formation. Chen, Q., Atkinson, A., Otsuga, D., Christensen, T., Reynolds, L., and Drews, G.N. Development 1999 126, 715 2726.
METHOD AND APPARATUS FOR CLEANING OF VIABLE DONOR SOFT TISSUE. Inventors: Christensen TW , Burns DC, Humphrey, RJ, Eisenhut AR, Christopher R. U.S. Patent # 8,034,288
STERILIZATION OF DRUGS USING SUPERCRITICAL CARBON DIOXIDE STERILANT. Inventors: Christensen TW , Burns DC, Humphrey, RJ, Eisenhut AR, U.S. Patent # 8,012,414
INACTIVATING ORGANISMS USING CARBON DIOXIDE AT OR NEAR ITS SUPERCRITICAL PRESSURE AND TEMPERATURE CONDITIONS Inventor: Christensen; Timothy Wayne, U.S. Patent # 7,560,113
STERILIZATION METHODS AND APPARATUS WHICH EMPLOY ADDITIVE-CONTAINING SUPERCRITICAL CARBON DIOXIDE STERILANT Inventors: Christensen; Timothy Wayne , Burns; David Carroll, White; Angela Lydia, Ganem; Bruce , Eisenhut; Anthony Romey, U.S. Patent # 7,108,832
Divya Devadasan, M.S., Casi Strickland, B.S, Chad Hunter M.S.,
Samantha Mandel, B.S., Jeff Chmielewski, M.S., Laura Henderson M.S.,
Lena Keller: Undergrad, Hannah Cantrell B.S., Tabitha Reel B.S.,
Justin Gosnell M.S., Jennifer Apger M.S., Catherine Gouge M.S.