In vivo Analyse der Struktur von Chromosomenterritorien: Dyanamische Veränderungen während des Zellzyklus und der terminalen Differenzierung von Zellen

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Gene rich and gene poor fractions of genomic DNA can be differentially labeled in living mammalian cells by the incorporation of thymidine analogs conjugated to fluorophores with different emission spectra during early and mid to late S-phase. These two fractions represent the R- and G/C-bands of mitotic chromosomes and form 'polarized' chromosome territories in interphase nuclei with gene poor and transcriptionally largely inactive G-foci clustered in the nuclear periphery and around the nucleoli, while R-foci form a gene rich and transcriptionally competent interior nuclear compartment (Sadoni et al., 1999). 5-10 cell cycles after in vivo labeling cell nuclei with few labeled chromatid territories emerge as a consequence of random segregation of fluorescently labeled and unlabeled chromatids (Zink et al., 19998; 1999). Our approach for the first time allows studies of chromatin arrangements and their dynamics in single living cells at the level of individual, double labeled chromosomes. Based on the progress we have achieved in our understanding of the higher order nuclear architecture during the first funding period, we will focus our studies during the second period on the question of changes of the higher order architecture and arrangements of mitotic chromosomes and chromosome territories, respectively, when cells proceed through the cell cycle or exit the cell cycle into GO or for terminal differentiation.