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Yuval Garini

Publications and source records attributed to Yuval Garini.

11 recordsLinked to original sources
PubMed2026

Telomeres in Lamin-A-depleted cells exhibit directed motion and dynamic coherence.

Investigating the dynamics of chromatin loci and the factors that influence them provides valuable insights into the organization and functionality of the genome within the cell nucleus. We control the expression of Lamin-A, an important organizer of chromatin and nuclear structure. By simultaneously tracking hundreds of telomeres in Lamin-A knockout (KO) and wild-type (WT) nuclei, we find that telomere motion in Lamin-A-depleted cells is both faster and more directed on micrometer scales, comparable to the size of chromosome territories. In contrast, telomere trajectories in WT cells exhibit pronounced anti-persistent behavior, consistent with caging by the surrounding chromatin environment. We further observe correlated motion between distinct telomeres in both WT and KO cells, with significantly stronger correlations in the KO case, indicating enhanced collective behavior. These correlations reflect cross-correlations among different loci rather than temporal correlations along individual trajectories. Together, these findings highlight the central role of Lamin-A in regulating both local confinement and collective telomere dynamics.

Telomere↗
PubMed2006

Changes in lamina structure are followed by spatial reorganization of heterochromatic regions in caspase-8-activated human mesenchymal stem cells.

Apoptosis is fundamental to the regulation of homeostasis of stem cells in vivo. Whereas the pathways underlying the molecular and biochemical details of nuclear breakdown that accompanies apoptosis have been elucidated, the precise nature of nuclear reorganization that precedes the demolition phase is not fully understood. Here, we expressed an inducible caspase-8 in human mesenchymal stem cells, and quantitatively followed the early changes in nuclear organization during apoptosis. We found that caspase-8 induces alteration of the nuclear lamina and a subsequent spatial reorganization of both centromeres, which are shifted towards a peripheral localization, and telomeres, which form aggregates. This nuclear reorganization correlates with caspase-3 sensitivity of lamina proteins, because the expression of lamin mutant constructs with caspase-3 hypersensitivity resulted in a caspase-8-independent appearance of lamina intranuclear structures and telomere aggregates, whereas application of a caspase inhibitor restrains these changes in nuclear reorganization. Notably, upon activation of apoptosis, we observed no initial changes in the spatial organization of the promyelocytic leukemia nuclear bodies (PML-NBs). We suggest that during activation of the caspase-8 pathway changes in the lamina structure precede changes in heterochromatin spatial organization, and the subsequent breakdown of lamina and PML-NB.

Blotting, Western↗
PubMed2006

Spectral imaging: principles and applications.

BACKGROUND: Spectral imaging extends the capabilities of biological and clinical studies to simultaneously study multiple features such as organelles and proteins qualitatively and quantitatively. Spectral imaging combines two well-known scientific methodologies, namely spectroscopy and imaging, to provide a new advantageous tool. The need to measure the spectrum at each point of the image requires combining dispersive optics with the more common imaging equipment, and introduces constrains as well. METHODS AND RESULTS: The principles of spectral imaging and a few representative applications are described. Spectral imaging analysis is necessary because the complex data structure cannot be analyzed visually. A few of the algorithms are discussed with emphasis on the usage for different experimental modes (fluorescence and bright field). Finally, spectral imaging, like any method, should be evaluated in light of its advantages to specific applications, a selection of which is described. CONCLUSIONS: Spectral imaging is a relatively new technique and its full potential is yet to be exploited. Nevertheless, several applications have already shown its potential.

Algorithms↗
PubMed2006

The significance of telomeric aggregates in the interphase nuclei of tumor cells.

Telomeres are TTAGGG repetitive motifs found at the ends of vertebrate chromosomes. In humans, telomeres are protected by shelterin, a complex of six proteins (de Lange [2005] Genes Dev. 19: 2100-2110). Since (Müller [1938] Collecting Net. 13: 181-198; McClintock [1941] Genetics 26: 234-282), their function in maintaining chromosome stability has been intensively studied. This interest, especially in cancer biology, stems from the fact that telomere dysfunction is linked to genomic instability and tumorigenesis (Gisselsson et al. [2001] Proc. Natl. Acad. Sci. USA 98: 12683-12688; Deng et al. [2003] Genes Chromosomes Cancer 37: 92-97; DePinho and Polyak [2004] Nat. Genetics 36: 932-934; Meeker et al. [2004] Clin. Cancer Res. 10: 3317-3326). In the present overview, we will discuss the role of telomeres in genome stability, recent findings on three-dimensional (3D) changes of telomeres in tumor interphase nuclei, and outline future avenues of research.

Animals↗
PubMed2005

Oncogenic remodeling of the three-dimensional organization of the interphase nucleus: c-Myc induces telomeric aggregates whose formation precedes chromosomal rearrangements.

The three-dimensional (3D) organization of the normal interphase nucleus permits the regulated completion of transcription and replication and assures proper chromosome organization. Aberrations from the normal 3D structural order of the nucleus are found in tumor cells. When examining the 3D organization of telomeres in nuclei of normal and tumor cells, we found that telomeres of normal nuclei do not overlap, while telomeres of tumor cells form aggregates of various numbers and sizes. To understand how such changes occur and what their implications are we have recently examined the role of the oncoprotein c-Myc in inducing changes in the 3D nuclear organization of telomeres. We found that c-Myc remodels the organization of telomeres and chromosomes in the interphase nucleus. It induces the formation of telomeric aggregates and fusions that are followed by breakage-bridge fusion cycles, and lead to the onset of chromosomal rearrangements that are typical of tumor cells.

Animals↗
PubMed2005

Electroosmotic flow analysis of a branched U-turn nanofluidic device.

In this paper, we present the analysis of electroosmotic flow in a branched -turn nanofluidic device, which we developed for detection and sorting of single molecules. The device, where the channel depth is only 150 nm, is designed to optically detect fluorescence from a volume as small as 270 attolitres (al) with a common wide-field fluorescent setup. We use distilled water as the liquid, in which we dilute 110 nm fluorescent beads employed as tracer-particles. Quantitative imaging is used to characterize the pathlines and velocity distribution of the electroosmotic flow in the device. Due to the device's complex geometry, the electroosmotic flow cannot be solved analytically. Therefore we use numerical flow simulation to model our device. Our results show that the deviation between measured and simulated data can be explained by the measured Brownian motion of the tracer-particles, which was not incorporated in the simulation.

Computer Simulation↗
PubMed2005

c-Myc induces chromosomal rearrangements through telomere and chromosome remodeling in the interphase nucleus.

In previous work, we showed that telomeres of normal cells are organized within the 3D space of the interphase nucleus in a nonoverlapping and cell cycle-dependent manner. This order is distorted in tumor cell nuclei where telomeres are found in close association forming aggregates of various numbers and sizes. Here we show that c-Myc overexpression induces telomeric aggregations in the interphase nucleus. Directly proportional to the duration of c-Myc deregulation, we observe three or five cycles of telomeric aggregate formation in interphase nuclei. These cycles reflect the onset and propagation of breakage-bridge-fusion cycles that are initiated by end-to-end telomeric fusions of chromosomes. Subsequent to initial chromosomal breakages, new fusions follow and the breakage-bridge-fusion cycles continue. During this time, nonreciprocal translocations are generated. c-Myc-dependent remodeling of the organization of telomeres thus precedes the onset of genomic instability and subsequently leads to chromosomal rearrangements. Our findings reveal that c-Myc possesses the ability to structurally modify chromosomes through telomeric fusions, thereby reorganizing the genetic information.

Animals↗
PubMed2005

From micro to nano: recent advances in high-resolution microscopy.

Improving the spatial resolution of optical microscopes is important for a vast number of applications in the life sciences. Optical microscopy allows intact samples and living cells to be studied in their natural environment, tasks that are not possible with other microscopy methods (e.g. electron microscopy). Major advances in the past two decades have significantly improved microscope resolution. By using interference and structured light methods microscope resolution has been improved to approximately 100 nm, and with non-linear methods a ten times improvement has been demonstrated to a current resolution limit of approximately 30 nm. These methods bring together old theoretical concepts such as interference with novel non-linear methods that improve spatial resolution beyond the limits that were previously assumed to be unreachable.

Image Enhancement↗
PubMed2004

The three-dimensional organization of telomeres in the nucleus of mammalian cells.

BACKGROUND: The observation of multiple genetic markers in situ by optical microscopy and their relevance to the study of three-dimensional (3D) chromosomal organization in the nucleus have been greatly developed in the last decade. These methods are important in cancer research because cancer is characterized by multiple alterations that affect the modulation of gene expression and the stability of the genome. It is, therefore, essential to analyze the 3D genome organization of the interphase nucleus in both normal and cancer cells. RESULTS: We describe a novel approach to study the distribution of all telomeres inside the nucleus of mammalian cells throughout the cell cycle. It is based on 3D telomere fluorescence in situ hybridization followed by quantitative analysis that determines the telomeres' distribution in the nucleus throughout the cell cycle. This method enables us to determine, for the first time, that telomere organization is cell-cycle dependent, with assembly of telomeres into a telomeric disk in the G2 phase. In tumor cells, the 3D telomere organization is distorted and aggregates are formed. CONCLUSIONS: The results emphasize a non-random and dynamic 3D nuclear telomeric organization and its importance to genomic stability. Based on our findings, it appears possible to examine telomeric aggregates suggestive of genomic instability in individual interphase nuclei and tissues without the need to examine metaphases. Such new avenues of monitoring genomic instability could potentially impact on cancer biology, genetics, diagnostic innovations and surveillance of treatment response in medicine.

Animals↗
PubMed2004

Fourier transformed spectral bio-imaging for studying the intracellular fate of liposomes.

BACKGROUND: To improve the efficiency of liposomal drug targeting systems, it is necessary to understand the mechanism of liposome uptake by the cell and to follow the intracellular fate of internalized liposomes and their contents. METHODS: We applied multiple-color fluorescence imaging spectroscopy, using a combination of five fluorescent dyes with a significant spectral overlap. pH-sensitive liposomes were labeled with the hydrophilic dye fluorescein isothiocyanate-dextran (FITC-dextran) or the lipophilic membrane marker rhodamine-B-phosphoethanolamine (Rh-PE) and incubated with COS-7 cells. Further, the cells were stained with specific markers: the cell membrane was fluorescently labeled with Vybrant DiO, lysosomes were stained with LysoTracker Red, and 4',6 diamidino-2-phenylindole dihydrochloride was used for counterstaining the nucleus. RESULTS: All five dyes were used simultaneously and were spectrally distinguished by the system. FITC-dextran-labeled liposomes showed a distribution pattern different from identically composed liposomes labeled with Rh-PE: the highly lipophilic Rh-PE was colocalized with the lysosomotropic dye LysoTracker Red, whereas liposomal FITC-dextran was not accompanied by LysoTracker Red in all cases. CONCLUSIONS: (a) Spectral (bio-) imaging is a powerful method for studying the intracellular fate of liposomal compounds. (b) We assume that the liposome membrane marker Rh-PE influences the uptake of particles due to its surface-modifying properties. We propose that this head-group-labeled phospholipid acts as a ligand for cellular receptors and triggers receptor-mediated (clathrin-dependent) endocytosis.

Algorithms↗