Currently Funded Project Descriptions

Effects Of Low Doses of Radiation on DNA Repair
Jointly funded by NASA and DOE
Eric J Ackerman
Pacific Northwest National Laboratory
Richland, WA 99352
Dr. Ackerman will study the effect of low doses of ionizing radiation on the repair of different types of damage to DNA, including damage from ionizing radiation and that produced by the normal internal operation of the cell. Using a very sensitive technique called host cell reactivation assay (HCR), he will quantitatively measure the repair of each type of DNA damage and thereby measure if the cellular repair system itself has been damaged. He will also determine
if unique forms of DNA repair system damage are induced by low doses of cosmic radiation exposure present during space missions.

Cellular Responses to Low Dose/Very Low Dose Rate Ionizing Radiation: The Role of Endogenous Oxidative Metabolism
Edouard I. Azzam
New Jersey Medical School
Newark, NJ 07103
This project will investigate the involvement of oxidation-reduction (redox) reactions that are part of normal metabolism in the biological response to low dose, low dose rate gamma-ray exposures. Dr. Azzam and colleagues will measure chromosome damage and the rate of telomere loss (the structures at the end of chromosomes) in a novel three-dimensional tissue-like system to study biological damage and antioxidant capacity inside irradiated cells. This research will address the hypothesis that a cell's metabolic status helps determine its response to radiation by modulating the signaling pathways.

Genetic factors affecting susceptibility to low dose and low dose rate radiation exposure
Joel S. Bedford
Department of Environmental and Radiological Health Sciences
Colorado State University, Fort Collins, Colorado

Multi-Cellular Crosstalk in Radiation Damage
Eleanor A. Blakely
Lawrence Berkeley National Laboratory
Berkeley, CA 94720
Cellular communication is essential to maintain normal tissue function. Dr. Blakely will examine how low doses of X-ray radiation can perturb normal messages sent between cells, resulting in aberrant behavior of neighboring undamaged cells as well as those directly effected by radiation exposure. In these experiments she will use the X-ray Microprobe at the Advanced Light Source at LBNL to precisely irradiate individual cells and specific regions in cells without damaging neighboring cells. This exposure system will be combined with a microarray technology to determine which genes are turned on or off in both "hit and "non-hit" cells.

The Adaptive Response in p53 Cancer-Prone Mice: Loss of Heterozygosity and Chromosome Instability
Douglas R. Boreham
McMaster University
Ontario, Canada L8S4K1
Dr. Boreham will examine two genetic endpoints in the cells of mice chronically irradiated by very low doses of gamma rays, to test whether an adaptive response is induced. This small, one year study will be combined with a larger study already underway in Canada, involving several thousand mice. The larger study, funded by Atomic Energy of Canada Limited in collaboration with McMaster University and Health Canada, is investigating the effects of low dose and low dose rate exposures on the major endpoints of longevity, cancer frequency, and cancer latency in mice. This new study will provide insights into biological mechanisms that may, in part, be responsible for the observed frequency of induction of theses major endpoints.

Mechanisms of Low-Dose Inducible DNA Repair and Adaptive Response
Priscilla K. Cooper
Lawrence Berkeley National Laboratory
Berkeley, CA 94720
Dr. Cooper will identify and characterize human genes that are critical for responses to exposure to low level ionizing radiation. Specifically she will investigate a network of proteins involved in repairing damage to DNA, as the DNA is undergoing a process called transcription (the process producing copies of RNA that are used as templates to produce proteins). The molecules involved in transcription-coupled repair will be examined for their participation in the adaptive effect, an effect whereby exposure to a small initial dose of radiation reduces the effect of a much larger second radiation dose.

Cytogenetic Response of Low Doses of Ionizing Radiation
Jointly funded by NASA and DOE
Michael N Cornforth
University of Texas, Medical Branch (UTMB)
Galveston, TX 77555-0656
Using advanced fluorescent imaging techniques (mFISH) that makes it possible to identify each chromosome pair within the nucleus, Dr. Cornforth and co-workers will investigate the competition between different types of cellular DNA repair systems. They will study a variety of cytogenetic endpoints, including hromosome aberrations, under conditions that favor one type of repair system over another. The studies may eventually make it possible to retrospectively determine the type of radiation involved in individual exposures.

Molecular Energetics of Clustered Damage Sites
Michel Dupuis
Pacific Northwest National Laboratory
Richland, WA 99352
Dr. Dupuis and colleagues will undertake studies to compare the similarities and differences between damage to DNA caused by normal cellular processes, such as endogenous oxidative damage, and those caused by ionizing radiation. Using the state-of-the-art computational chemistry models involving quantum chemical and molecular dynamics simulations, Dr. Dupuis will describe the pertinent chemical character of DNA damage at a single site versus multiple damage sites clustered close together.

Low Dose Response of Respiratory Cells in Intact Tissues and Reconstituted Tissue Constructs
Jointly funded by NASA and DOE
John R. Ford
Texas Engineering Experiment Station
Texas A & M University
College Station, TX 77843-3133
Dr. Ford is using the well-established rat trachea model to test the hypothesis that normal respiratory epithelial cells transmit signals to neighboring cells in response to very low dose radiation exposure. Tracheal tissue will be irradiated with a highly collimated electron microbeam irradiator or with a single-particle positive ion microbeam irradiator. Changes will be measured in DNA repair-related protein expression, apoptosis, and in proteins involved in cell cycle regulation (cyclin) in both the irradiated cells and in the neighboring, unirradiated cells. Dr. Ford's team will compare the responses shown by cells in these normal rodent respiratory tissues to those seen for human respiratory epithelial cells in reconstituted tissue constructs, and will characterize responses after a variety of radiation types.

Low Dose Gamma Irradiation Potentiates Secondary Exposure to Gamma Rays or Protons in Thyroid Tissue Analogs
Jointly funded by NASA and DOE
Lora M. Green
Radiobiology Program
Loma Linda University
Loma Linda, CA 92354
Using a reconstituted three-dimensional tissue model derived from rat thyroid (FRTL-5) tissue Dr. Green and colleagues will address both radiation-induced adaptive response (a potentially protective low dose phenomenon) and effects in neighboring unirradiated cells. These investigators hypothesize that homeostatic processes are responsible for the adaptive responses triggered by exposure to low doses of radiation. Following irradiation using various exposure protocols, the reconstituted tissues will be characterized for the profile of genes that they express. Effects of irradiation on bystander cells will be addressed using a micro-collimated high-energy proton beam irradiator.

Mechanisms of the Bystander Effect
Jointly funded by NASA and DOE
Eric J. Hall
Columbia University
New York, NY 10032
This project will determine if the bystander effects occurs in a three-dimensional cell cluster model composed of two mammalian cell types. A bystander effect is defined when only a few cells within a population are irradiated, and neighboring unirradiated cells (or bystanders) also respond, presumably via a signal from the irradiated cells. This response has been observed in monolayer cell culture but not yet in 3D cell culture or tissues. Dr. Hall and colleagues will measure mutation frequency, gene expression, and clonal survival as a function of cell type and irradiation status. Both electron and alpha particle radiations will be used to provide the low dose exposures.

SATB1 Deficiency Accounts for High Susceptibility to Low Dose Radiation
Jointly funded by NASA and DOE
Terumi Kohwi-Shigematsu
Lawrence Berkeley National Laboratory
Berkeley, CA 94720
Dr. Kohwi-Shigematsu will test whether the amount and quantity of a specific protein, SATB1, helps determine an individual's sensitivity to radiation. This protein acts as a "landing platform" for other proteins that regulate which genes are turned on or off in a cell. The SATB1 gene will be studied in immune system cells that have an altered response to ionizing radiation. The radiation response of cells that have no copies or only one copy of the gene for SATB1 will be compared to the response of normal cells with two copies of the gene. The role of the number of copies the SATB1 gene in the cellular localization of DNA repair proteins will be also examined as a function of radiation exposure.

Genetic Factors Affecting Susceptibility to Low-Dose Radiation
William F. Morgan
University of Maryland
Baltimore, MD 21201-1559
Dr. Morgan and colleagues will continue an ongoing study to test how mice that have a radiation-sensitizing mutation in one of several genes develop cancer. Specifically, they are testing whether cancer development is the result of triggering a chromosome breakage pathway and inducing genomic instability following exposure to low doses of radiation, a mechanism already demonstrated for high doses. The mice in the study were bred to be homozygous (two mutant copies), heterozygous (one mutant copy, one normal copy), or normal (two normal
copies). The study will provide insights on the role of mutations in a single gene in determining an individual's increased sensitivity to radiation.

Molecular Characterization of Survival Advantage Bystander Effect & Genomic Instability After Low LET Low Dose Radiation Exposure
Mohan Natarajan
University of Texas
San Antonio, TX 78229-3900
This project will determine if a specific cell-signaling mechanism is responsible for a previously observed low dose radiation-induced survival advantage. Dr. Natarajan will test the hypothesis that low dose radiation triggers the activation of a DNA transcription factor, NF-kB, which in turn initiates a tumor necrosis factor alpha mediated bystander effect. Results from this study will provide further insights on the range of biological response to radiation and may also influence current understanding of angiogenesis (the generation of new blood vessels), important in the development of cancer.

Genetic Variation in Tissue Responses to Low Dose Radiation
Eugene Rinchik
Oak Ridge National laboratory
Oak Ridge, TN 37831-8077
Mice can be mated over several generations to produce a group of animals with an almost identical set of genes (inbreeding). Dr. Rinchik will expose groups of inbred mice, each group genetically different from the others, to low dose radiation. The research will examine whether the genetic response of one inbred group of mice differs from other genetically different inbred mice, using high-throughput technologies such as microarrays. The differences in the genetic
response will be associated where possible with differences in sensitivity to radiation of the mice, and thus candidate genes that influence radiation sensitivity may be identified.

Transcriptional and Radio-adaptive Responses to Low Dose Rate Environmental Exposures to the Radioactive Fallout at Chornobyl
Brenda E. Rodgers
Texas Tech University
Lubbock, TX 79409-3131
Dr. Rodgers and colleagues will study biological responses in the tissues of mice exposed to the low dose and low dose rate radiation from an actual Chornobyl fallout environment. Potential molecular mechanisms responsible for previously observed adaptive responses will be tested, and gene expression and DNA damage will be measured. Additional tissues and nucleic acid samples from the exposed mice will also be archived as a resource for future studies.

DNA Damage Clusters in Low Level Radiation Responses of Human Cells
Jointly funded by NASA and DOE
Betsy M. Sutherland
Brookhaven National Laboratory
Upton, NY 11973
Dr. Sutherland has developed powerful techniques for measuring and quantifying localized clusters of DNA damage. DNA damage occurs both during the normal internal operation of a cell and from external events such as ionizing radiation exposure. If damage is sparse, the normally double-stranded DNA seems to repair easily. If the damage sites are very close together both DNA strands might break, resulting in a greater chance of serious biological effects. Dr. Sutherland will study how clustered damage is repaired, whether unrepaired clustered damage leads to genetic damage, and whether clustered damage arising from normal cellular processes can be related to cell survival.

Murine Models of Radiation Sensitivity
Michael M. Weil
University of Texas M.D. Anderson Cancer Center
Houston, TX 77030-4095
This one-year pilot study will create sets of mutagenized mouse embryonal stem cell lines that can be screened for dominant and recessive defects in their response to radiation. If successful, Dr. Weil proposes additional studies to determine if these mutations correspond to useful phenotypes in intact mice that can then be used to study the genetics of low dose radiation sensitivity for cancer induction.

Low LET Radiation Studies on the Protective Bystander Effect in an Organized Tissue
Basil V. Worgul
Columbia University
New York, NY 10032
Dr. Worgul will conduct low dose radiation studies of the rat lens epithelium, a highly organized three-dimensional tissue. In addition to measuring cataract formation and several cellular endpoints, molecular studies will be conducted on the role of gap junctions and soluble molecular signaling factors in the communication between irradiated cells and their unirradiated cell neighbors within the lens epithelium.