University of Essen FB9 Department of Genetics Universitätsstr. 5 D-45117 Essen (Germany)

1. University of EssenFB9 Department of GeneticsUniversitätsstr. 5D-45117 Essen (Germany) Chromosomal Aberrations in Blood Lymphocytes of Astronauts Principal Investigator: Prof. Dr. Günter Obe Co-Investigators: Markus Horstmann Dr. Christian Johannes

2. The genetic material is mainly situated in chromosomes Scientific Background Body cells contain 2x23 chromosomes (2n=46) Cultured lymphocytes undergo mitosis which allows to prepare chromosomes and analyze them with the light microscope Changes in the morphology of chromosomes (chromosomal aberrations, chromosome mutations) can be recognized and quantified

3. Scientific Background DNA is damaged by ionizing radiation, which may lead to chromosomal aberrations Chromosomal aberrations may lead to an elevated risk of cancer Frequencies of chromosomal aberrations depend on characteristics and doses of ionizing radiation

4. Lesions in chromosomal DNA following treatment with mutagenic carcinogens(From G . Obe and A.T. Natarajan, 1982)

5. Radiation induced DNA damage gamma-, beta-, X-rays (low LET) alpha-, neutron rays (high LET) Dose effect relationships for dicentrics and translocations following exposure to low or high LET radiation (From G. Obe and A. T. Natarajan, 1999)

6. Metaphase preparation from human lymphocytes(Giemsa staining) a: Undamaged metaphase b: Radiation induced dicentric chromosome (left) with fragment (top right)

7. Multiaberrant Cell (Giemsa staining) Arrowheads indicate centromeres in poly- centric chromosomes

8. Human metaphase chromosomes “painted” with the mFISH method Reciprocal exchange (translocation between chromosomes 11 and 12)

9. Chromosome 5 „painted“ with the mBAND method The right chromosome shows a large inversion of its middle part whose breakpoints are indicated by dotted lines. (White dots = centromeres)

10. Chromosomal aberrations in peripheral blood lymphocytes of astronauts indicate an elevated mutagenic and carcinogenic risk due to radiation in space Scientific Background Result

11. Dicentric chromosomes in lymphocytes of seven MIR cosmonauts (C1-C7) before and after their last space flight (120-198 days). (Data from: Obe et al, 1997) The frequencies of dicentrics can be calculated by taking radiobiological parameters such as half-life of lymphocytes and dose-effect characteritics into account.

14. The analysis of chromosomal aberrations in lymphocytes of astronauts allows to answer the following questions: 1. Is exposure to space radiation associated with mutagenic and carcinogenic risks ? 2. What radiation protection measures have to be taken to minimize risks of exposures to space radiation ? Conclusions

15. To assess the genetic impact of ionizing radiations, blood (10-15 ml) is drawn before and shortly after flights by venous puncture Blood cultures will be set up in our laboratory, using standard procedures Chromosomes will be stained using procedures to assess all types of aberrations: (1) Classical Giemsa staining (2) Multi-color fluorescence in situ hybridization (mFISH) (3) Multi-color banding fluorescence in situ hybridization (mBAND) of chromosome 5 Experiment Design

16. Venipuncture performed by a physician is nearly free of any risk. Minor temporary discomfort or pain. Hematoma associated with extravasation of blood during or following venipuncture. Infection or thrombophlebitis resulting from venipuncture. This is infrequent in healthy persons. The following safety precautions will be taken to mitigate any risk associated with venipuncture: Procedure will be performed by experienced personnel. Use of standard aseptic techniques. Use of sterile disposable hardware. Possible Inconveniences or Discomforts No additional inconveniences or discomforts have been identified. Medical Risks