Biomedical subjects

Daniel Gerlich

Publications and source records attributed to Daniel Gerlich.

7 recordsLinked to original sources

PubMed2003

Global chromosome positions are transmitted through mitosis in mammalian cells.

We investigated positioning of chromosomes during the cell cycle in live mammalian cells with a combined experimental and computational approach. By non-invasive labeling of chromosome subsets and tracking by 4D imaging, we could show that no global rearrangements occurred in interphase. Using the same assay, we also observed a striking order of chromosomes throughout mitosis. By contrast, our computer simulation based on stochastic movements of individual chromosomes predicted randomization of chromosome order in mitosis. In vivo, a quantitative assay for single chromosome positioning during mitosis revealed strong similarities between daughter and mother cells. These results demonstrate that global chromosome positions are heritable through the cell cycle in mammalian cells. Based on tracking of labeled chromosomes and centromeres during chromosome segregation and experimental perturbations of chromosomal order, we propose that chromosome specific timing of sister chromatid separation transmits chromosomal positions from one cell generation to the next.

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PubMed2003

Dynamics of chromosome positioning during the cell cycle.

The arrangement and dynamics of chromosomes inside the nucleus of mammalian cells have been studied intensively over the last two years. Although chromosomes are relatively immobile and occupy non-random positions in interphase, their dynamic movements in mitosis have traditionally been assumed to randomize this arrangement. New methods of live cell imaging now make it possible to follow chromosome movements directly and quantitatively in single cells. Such studies have generated models of chromosome positioning throughout the cell cycle and provide a new basis to address the underlying mechanisms in future experiments.

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PubMed2003

Quantitative motion analysis and visualization of cellular structures.

The availability of cellular markers tagged with the green fluorescent protein (GFP) has recently allowed a large number of cell biological studies to be carried out in live cells, thereby addressing the dynamic organization of cellular structures. Typically, microscopes capable of video recording are used to generate time-resolved data sets. Dynamic imaging data are complex and often difficult to interpret by pure visual inspection. Therefore, specialized image processing methods for object detection, motion estimation, visualization, and quantitation are required. In this review, we discuss concepts for automated analysis of multidimensional image data from live cell microscopy and their application to the dynamics of cell nuclear subcompartments.

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PubMed2003

4D imaging to assay complex dynamics in live specimens.

A full understanding of cellular dynamics is often difficult to obtain from time-lapse microscopy of single optical sections. New microscopes and image-processing software are now making it possible to rapidly record three-dimensional images over time. This four-dimensional imaging allows precise quantitative analysis and enhances visual exploration of data by allowing cellular structures to be interactively displayed from many angles. It has become a key tool for understanding the complex organization of biological processes in live specimens.

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PubMed2002

Nuclear envelope breakdown proceeds by microtubule-induced tearing of the lamina.

The mechanism of nuclear envelope breakdown (NEBD) was investigated in live cells. Early spindle microtubules caused folds and invaginations in the NE up to one hour prior to NEBD, creating mechanical tension in the nuclear lamina. The first gap in the NE appeared before lamin B depolymerization, at the site of maximal tension, by a tearing mechanism. Gap formation relaxed this tension and dramatically accelerated the rate of chromosome condensation. The hole produced in the NE then rapidly expanded over the nuclear surface. NE fragments remaining on chromosomes were removed toward the centrosomes in a microtubule-dependent manner, suggesting a mechanism mediated by a minus-end-directed motor.

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PubMed2002

Stage-specific chromosomal association of Drosophila dMBD2/3 during genome activation.

The Drosophila gene dMBD2/3 encodes a protein with significant homologies to the mammalian methyl-DNA binding proteins MBD2 and MBD3. These proteins are essential components of chromatin complexes involved in epigenetic gene regulation. Because the available in vitro data on dMBD2/3 are conflicting we have started an in vivo characterization of dMBD2/3. We detected expression of two isoforms specifically during embryonic development. Staining of whole embryos combined with high-resolution confocal microscopy revealed a highly regulated spatial distribution. During the syncytial blastoderm stage, dMBD2/3 formed speckles that localized to the cytoplasm. Shortly after, during the cellular blastoderm stage, the protein entered the nucleus and formed bright foci that associated with DNA. This rapid transition coincided with the activation of the embryonic genome. A similar observation was made during activation of the spermatocyte genome as dMBD2/3 formed distinct foci associated with the activated Y chromosome. Our results indicate that dMBD2/3 forms specialized nuclear compartments to keep certain genes epigenetically silenced during genome activation.

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PubMed2002

Metabolic-energy-dependent movement of PML bodies within the mammalian cell nucleus.

Promyelocytic leukaemia (PML) nuclear bodies are present in most mammalian cell nuclei. PML bodies are disrupted by PML retinoic acid receptor alpha (RAR alpha) oncoproteins in acute promyelocytic leukaemia. These bodies contain numerous proteins, including Sp100, SUMO-1, HAUSP(USP7), CBP and BLM, and they have been implicated in aspects of transcriptional regulation or as nuclear storage depots. Here, we show that three classes of PML nuclear bodies can be distinguished, on the basis of their dynamic properties in living cells. One class of PML bodies is particularly noteworthy in that it moves by a metabolic-energy-dependent mechanism. This represents the first example of metabolic-energy-dependent transport of a nuclear body within the mammalian cell nucleus.

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