SPECTRAL PRECISION DISTANCE MEASUREMENTS BY CONFOCAL LASER SCANNING AND SME-MICROSCOPY FOR 3D GENOME ANALYSIS

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1 95 SPECTRAL PRECISION DISTANCE MEASUREMENTS BY CONFOCAL LASER SCANNING AND SME-MICROSCOPY FOR 3D GENOME ANALYSIS C. Cremer 1, J. Rauch 1, P. Edelmann 1, H. Bornfleth 1, B. Schneider 1,I. Upmann 1, J. BradI 2, S. Dietzel 3, I. Solovei 4, T. A. Knoch 5, J. Langowski 5, T. Cremer 4, M. Hausmann 1 1 = Institut für Angewandte Physik, Universität Heidelberg; 2 = Leica Lasertechnik, Heidelberg; 3 = ZMBH, Heidelberg; 4=lnstitut für Anthropologie und Humangenetik, LMU München; 5 = DKFZ, Heidelberg For the study of the three-dimensional (3D) structure of the human genome and its functional significance small DNA sequences can specifically be labelled in intact cell nuclei by fluorescence in situ hybridization. For the quantitative analysis of the topology of the labelled sites, far field light microscopes of high resolution and precision are required. For this, the technique of Spectral Precision Distance Microscopy (SPM) has been introduced. The principle (1) is based on the fact that the bary center of a labelled site can be localized with higher precision than the resolution (= full width at half maximum of the point spread function). If different labelled sites with distances below the resolution are discriminated by different spectral signatures, they can be localized independently and thus their distances can be determined. For a confocal laser scanning microscope, a "resolution equivalent" of about 50 nm corresponding to a few nucleosome diameters can be obtained. This, however, requires a calibration of imaging errors, especially the chromatic shift, by means of micro beads (2) or in situ by simultaneous multi color labelling (3). SPM was applied to study the positions of the Adenine Nucleotide Transferase genes ANT2 and ANT3 on both X-chromosomes (Xactive /Xinactive). ANT3 (on both chromosomes active) was found to be located close to the surface of both chromosome territories. In contrast, ANT2 was located near the surface of Xactive only (4). Using the same methodological principles, selected clones of the Prader-Willi-Region ofchromosome 15 were localized in human cell nuclei with highprecision and their distances were determined (5). To further increase the resolution equivalent (goal; i nucleosome diameter), a two laser spatially modulated excitation (SME) microscope was realized (6). The laser beams are coherently focused into the back focal planes of two objectives. Inthe object space a standing wave field for each wave lengthcan be obtained by constructive interference. The fluorescence labelled object is moved along the optical axis in steps of 20nm. At each position a complete 2D optical section is recorded. Thus, an intensity modulated image section can be generated along the optical axis. Using an appropriate fit function, the intensity bary centers and thus the objects can be localized with a precision of 1-2 nm. Preliminary results for test particles and labelling sites in cell nuclei (Prader- Willi-Region) are shown (7). Assumptions: 1. resolution 250 nm (in example) 2. error of localization (3D)of l(l 2)=20 nm Result: Distances below the optical resolution can be measured by SPM

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5 99 References 1. Schneider B, Bradl J, Kirsten I, Hausmann M, CremerC (1998) High precision localization of 8 fluorescent targets in the nanometer range by spatially modulated excitation fluorescence microscopy. In: Fluorescence Microscopy and Fluorescent Probes (J. Slavik, Ed.), Plenum Press, in press. 2. Cremer C, Bornfleth H, Bradl J, Esa A, Kreth G, Rinke B, Eils R, Münke lc. Dietzel S. Granzow M. Jauch A, Guan X-Y, Meltzer PS, Trent JM. Trakhtenbrot L, Zink D. Langowski J, Hausmann M. CremerT (1997) Nuclear architecture and the formation of chromosome aberrations. Radiat.Res.148: Hausmann M, Schneider B, Bradl J, Cremer C (1997) High-precision distance microscopy of 3 D-nanostructures by a spa tially modulated excitation fluorescence microscope. In: Optical Biopsies and Microscopic Techniques II, Proc.SPIE 3197: Hausmann M. Esa A. Edelmann P. Trakhtenbrot L, Bornfleth H, Schneider B, Bradl J, Ben-Bassat I, Rechavi G, Cremer C (1998) Advanced precision light microscopy for the analysis of 3D-nanostructures of chromatin breakpoint regions: Towards a structurefunction relationship of the bcr-abl region. In: Fundamentals for the Assessment of Risks from Envjronmental Radiation (Hrg.: G. Horneck) NATO-Asi Series, Kluwer Academic Publishers, Dordrecht, submitted 5. Cremer C, Edelmann P, Esa A, Bornfleth H. Schneider B, BradI J, Rinke B, Trakhtenbro L, Dietzel S, Hausmann M. CremerT (1997) Spektrale Präzisionsdistanzmikroskopie in der Genomforschung. Z. Med. Physik, submitted 6. Cremer C, Hausmann M, BradI J, Rinke B. Verfahren zur multispektralen Präzisionsdistanz messung in biologischen Mikroobjekten. Patent Application submitted, , Deutsches Patentamt 7. Bornfleth H. Sätzler K. Eils R, Cremer C (1998) High precision distance measurements and volume-conserving segmentation of objects near and below the resolution limit in threedimensional confocal fluorescence microscopy. J. Microscopy 189: Cremer C, BradI J, Rinke B, Schneider B, Bornfleth H, Eils R, Esa A. Dietzel S. Jauch A. Zink D, Craig J, Wolf D, Rauch J, Münkel C, Kreth G, Münch H. Trakhtenbrot L, Langowski J, Hausmann M. CremerT (1997) Quantitative analysis of the 30-structure of the genome in the human cell nucleus. Analyt. Cell. Pathol.13/2: Edelmann P, Bornfleth H, DietzeI S, Hausmann M. Cremer T, Cremer C (1997) Dreidimensionale Mehrfarben- Bildrekonstruktion zur Untersuchung der Position der Gene ANT2 und ANT3 auf menschlichen X-Chromosomenterritorjen. 10. Heidelberger Zytometrie Symposium, Heidelberg, Kurzfassung der Beitrage (ISSN ): 23