Ludger Klewes

Fus deficiency in mice results in defective B-lymphocyte development and activation, high levels of chromosomal instability and perinatal death

The gene FUS (also known as TLS (for translocated in liposarcoma) and hnRNP P2) is translocated with the gene encoding the transcription factor ERG-1 in human myeloid leukaemias. Although the functions of wild-type FUS are unknown, the protein contains an RNA-recognition motif and is a component of nuclear riboprotein complexes. FUS resembles a transcription factor in that it binds DNA, contributes a transcriptional activation domain to the FUS–ERG oncoprotein and interacts with several transcription factors in vitro. To better understand FUS function in vivo, we examined the consequences of disrupting Fus in mice. Our results indicate that Fus is essential for viability of neonatal animals, influences lymphocyte development in a non-cell-intrinsic manner, has an intrinsic role in the proliferative responses of B cells to specific mitogenic stimuli and is required for the maintenance of genomic stability. The involvement of a nuclear riboprotein in these processes in vivo indicates that Fus is important in genome maintenance.

Dynamic chromosomal rearrangements in Hodgkin’s lymphoma are due to ongoing three-dimensional nuclear remodeling and breakage-bridge-fusion cycles

Background Hodgkin’s lymphoma is characterized by the presence of mono-nucleated Hodgkin cells and bi- to multi-nucleated Reed-Sternberg cells. We have recently shown telomere dysfunction and aberrant synchronous/asynchronous cell divisions during the transition of Hodgkin cells to Reed-Sternberg cells.1 Design and Methods To determine whether overall changes in nuclear architecture affect genomic instability during the transition of Hodgkin cells to Reed-Sternberg cells, we investigated the nuclear organization of chromosomes in these cells. Results Three-dimensional fluorescent in situ hybridization revealed irregular nuclear positioning of individual chromosomes in Hodgkin cells and, more so, in Reed-Sternberg cells. We characterized an increasingly unequal distribution of chromosomes as mono-nucleated cells became multi-nucleated cells, some of which also contained chromosome-poor ‘ghost’ cell nuclei. Measurements of nuclear chromosome positions suggested chromosome overlaps in both types of cells. Spectral karyotyping then revealed both aneuploidy and complex chromosomal rearrangements: multiple breakage-bridge-fusion cycles were at the origin of the multiple rearranged chromosomes. This conclusion was challenged by super resolution three-dimensional structured illumination imaging of Hodgkin and Reed-Sternberg nuclei. Three-dimensional super resolution microscopy data documented inter-nuclear DNA bridges in multi-nucleated cells but not in mono-nucleated cells. These bridges consisted of chromatids and chromosomes shared by two Reed-Sternberg nuclei. The complexity of chromosomal rearrangements increased as Hodgkin cells developed into multi-nucleated cells, thus indicating tumor progression and evolution in Hodgkin’s lymphoma, with Reed-Sternberg cells representing the highest complexity in chromosomal rearrangements in this disease. Conclusions This is the first study to demonstrate nuclear remodeling and associated genomic instability leading to the generation of Reed-Sternberg cells of Hodgkin’s lymphoma. We defined nuclear remodeling as a key feature of Hodgkin’s lymphoma, highlighting the relevance of nuclear architecture in cancer.

Profiling Three-Dimensional Nuclear Telomeric Architecture of Myelodysplastic Syndromes and Acute Myeloid Leukemia Defines Patient Subgroups

Purpose: Myelodysplastic syndromes (MDS) are a group of disorders characterized by cytopenias, with a propensity for evolution into acute myeloid leukemias (AML). This transformation is driven by genomic instability, but mechanisms remain unknown. Telomere dysfunction might generate genomic instability leading to cytopenias and disease progression. Experimental Design: We undertook a pilot study of 94 patients with MDS (56 patients) and AML (38 patients). The MDS cohort consisted of refractory cytopenia with multilineage dysplasia (32 cases), refractory anemia (12 cases), refractory anemia with excess of blasts (RAEB)1 (8 cases), RAEB2 (1 case), refractory anemia with ring sideroblasts (2 cases), and MDS with isolated del(5q) (1 case). The AML cohort was composed of AML-M4 (12 cases), AML-M2 (10 cases), AML-M5 (5 cases), AML-M0 (5 cases), AML-M1 (2 cases), AML-M4eo (1 case), and AML with multidysplasia-related changes (1 case). Three-dimensional quantitative FISH of telomeres was carried out on nuclei from bone marrow samples and analyzed using TeloView. Results: We defined three-dimensional nuclear telomeric profiles on the basis of telomere numbers, telomeric aggregates, telomere signal intensities, nuclear volumes, and nuclear telomere distribution. Using these parameters, we blindly subdivided the MDS patients into nine subgroups and the AML patients into six subgroups. Each of the parameters showed significant differences between MDS and AML. Combining all parameters revealed significant differences between all subgroups. Three-dimensional telomeric profiles are linked to the evolution of telomere dysfunction, defining a model of progression from MDS to AML. Conclusions: Our results show distinct three-dimensional telomeric profiles specific to patients with MDS and AML that help subgroup patients based on the severity of telomere dysfunction highlighted in the profiles. Clin Cancer Res; 18(12); 3293–304. ©2012 AACR.

Nuclear remodeling as a mechanism for genomic instability in cancer.

This chapter focuses on the three-dimensional organization of the nucleus in normal, early genomically unstable, and tumor cells. A cause-consequence relationship is discussed between nuclear alterations and the resulting genomic rearrangements. Examples are presented from studies on conditional Myc deregulation, experimental tumorigenesis in mouse plasmacytoma, nuclear remodeling in Hodgkins lymphoma, and in adult glioblastoma. A model of nuclear remodeling is proposed for cancer progression in multiple myeloma. Current models of nuclear remodeling are described, including our model of altered nuclear architecture and the onset of genomic instability.

Novel automated three-dimensional genome scanning based on the nuclear architecture of telomeres.

Telomeres, the end of chromosomes, are organized in a nonoverlapping fashion and form microterritories in nuclei of normal cells. Previous studies have shown that normal and tumor cell nuclei differ in their 3D telomeric organization. The differences include a change in the spatial organization of the telomeres, in telomere numbers and sizes and in the presence of telomeric aggregates. Previous attempts to identify the above parameters of 3D telomere organization were semi‐automated. Here we describe the automation of 3D scanning for telomere signatures in interphase nuclei based on three‐dimensional fluorescent in situ hybridization (3D‐FISH) and, for the first time, define its sensitivity in tumor cell detection. The data were acquired with a high‐throughput scanning/acquisition system that allows to measure cells and acquire 3D images of nuclei at high resolution with 40× or 60× oil and at a speed of 10,000–15,000 cells h−1, depending on the cell density on the slides. The automated scanning, TeloScan, is suitable for large series of samples and sample sizes. We define the sensitivity of this automation for tumor cell detection. The data output includes 3D telomere positions, numbers of telomeric aggregates, telomere numbers, and telomere signal intensities. We were able to detect one aberrant cell in 1,000 normal cells. In conclusions, we are able to detect tumor cells based on 3D architectural profiles of the genome. This new tool could, in the future, assist in patient diagnosis, in the detection of minimal residual disease, in the analysis of treatment response and in treatment decisions.

Imaging chromatin nanostructure with binding-activated localization microscopy based on DNA structure fluctuations

Abstract Advanced light microscopy is an important tool for nanostructure analysis of chromatin. In this report we present a general concept for Single Molecule localization Microscopy (SMLM) super-resolved imaging of DNA-binding dyes based on modifying the properties of DNA and the dye. By careful adjustment of the chemical environment leading to local, reversible DNA melting and hybridization control over the fluorescence signal of the DNA-binding dye molecules can be introduced. We postulate a transient binding as the basis for our variation of binding-activated localization microscopy (BALM). We demonstrate that several intercalating and minor-groove binding DNA dyes can be used to register (optically isolate) only a few DNA-binding dye signals at a time. To highlight this DNA structure fluctuation-assisted BALM (fBALM), we applied it to measure, for the first time, nanoscale differences in nuclear architecture in model ischemia with an anticipated structural resolution of approximately 50 nm. Our data suggest that this approach may open an avenue for the enhanced microscopic analysis of chromatin nano-architecture and hence the microscopic analysis of nuclear structure aberrations occurring in various pathological conditions. It may also become possible to analyse nuclear nanostructure differences in different cell types, stages of development or environmental stress conditions.

Quantitative Superresolution Microscopy Reveals Differences in Nuclear DNA Organization of Multiple Myeloma and Monoclonal Gammopathy of Undetermined Significance

The mammalian nucleus has a distinct substructure that cannot be visualized directly by conventional microscopy. In this study, the organization of the DNA within the nucleus of multiple myeloma (MM) cells, their precursor cells (monoclonal gammopathy of undetermined significance; MGUS) and control lymphocytes of the representative patients is visualized and quantified by superresolution microscopy. Three‐dimensional structured illumination microscopy (3D‐SIM) increases the spatial resolution beyond the limits of conventional widefield fluorescence microscopy. 3D‐SIM reveals new insights into the nuclear architecture of cancer as we show for the first time that it resolves organizational differences in intranuclear DNA organization of myeloma cells in MGUS and in MM patients. In addition, we report a significant increase in nuclear submicron DNA structure and structure of the DNA‐free space in myeloma nuclei compared to normal lymphocyte nuclei. Our study provides previously unknown details of the nanoscopic DNA architecture of interphase nuclei of the normal lymphocytes, MGUS and MM cells. This study opens new avenues to understanding the disease progression from MGUS to MM. J. Cell. Biochem. 116: 704–710, 2015.

Abstract 2044: Three-dimensional nuclear telomeric architecture defines cytopenias of myelodysplastic syndrome and its transformation to acute myeloid leukemia

Proceedings: AACR 103rd Annual Meeting 2012‐‐ Mar 31‐Apr 4, 2012; Chicago, IL Background Myelodysplastic Syndromes (MDS) are a group of disorders characterized by cytopenias, with a propensity for evolution into Acute Myeloid Leukemias (AML). This transformation is governed by acquisition of additional mutations, which in turn is driven by genomic instability and epigenetic events. However, how genomic instability occurs in this disease remains unknown. Telomere dysfunction might be the generator of genomic instability leading to cytopenias and disease progression from MDS to AML. Methods We undertook a prospective pilot study of 95 patients to investigate the nuclear telomere organization in MDS (57 patients) and AML (38 patients). Three-dimensional (3D) quantitative fluorescent in situ hybridization was performed to label telomeres of bone marrow samples. Nuclear telomere organization was analyzed using TeloViewTM and TeloScanTM. Findings Our cohort was composed of 57 cases of MDS and 38 AML. MDS cohort was constituted of Refractory Anaemia with Multilineage Dysplasia (RCMD = 32 cases), Refractory Anaemia (RA = 12 cases), Refractory Anaemia with Excess of Blasts 1 and 2 (RAEB-1 = 8 cases; RAEB-2 =1 case), Refractory Anaemia with Ring Sideroblasts (RARS = 2 cases), MDS associated with isolated del(5q) (1 case), and MDS unclassified (MDS-U = 1 case). AML were composed of AML-M4 (12 cases), AML-M2 (10 cases), AML-M5 (5 cases), AML-M0 (5 cases), AML-M1 (2 cases), AML-M4eo (1 case), and AML with multidysplasia related changes (1 case). We analyzed the 3D nuclear telomeric architecture, and determined the telomere numbers, presence of telomere aggregates, telomere signal intensities, nuclear volume, and telomere distribution. From these parameters we constructed 3D telomeric profiles, and we were able to subdivide the MDS patients into 9 subgroups and the AML patients into 6 subgroups. Each of the quantitative telomere parameters showed significant difference between MDS and AML. Furthermore, statistical analyses combining all the telomere parameters displayed significant difference between all subgroups. These profiles were linked to the evolution of telomere dysfunction in these subgroups allowing us to define a model of progression of MDS to AML. Our 3D telomeres profiling reflect better genomic abnormalities in MDS and AML than the cytogenetic categorisations. Telomere profiles seem to be a potential biomarker, which will improve the clinical management of these patients combined to other indexes such as IPSS and WPSS in MDS, and the cytogenetic risk factor classifications of AML. Interpretation Our results define for the first time the chronological and evolutionary process of telomere dysfunction in MDS and AML. These results are consistent with the hypothesis that telomere dysfunction generates genomic instability, leading to worsening cytopenias and to the transformation of MDS to AML. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 103rd Annual Meeting of the American Association for Cancer Research; 2012 Mar 31-Apr 4; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2012;72(8 Suppl):Abstract nr 2044. doi:1538-7445.AM2012-2044

Distinct and shared three-dimensional chromosome organization patterns in lymphocytes, monoclonal gammopathy of undetermined significance and multiple myeloma.

The consistent appearance of specific chromosomal translocations in multiple myeloma has suggested that the positioning of chromosomes in the interphase nucleus might play a role in the occurrence of particular chromosomal rearrangements associated with malignant transformation. Using fluorescence in situ hybridization, we have determined the positions of selected chromosome pairs (18 and 19, 9 and 22, 4 and 14, 14 and 16, 11 and 14) in interphase nuclei of myeloma cells compared to normal lymphocytes of treatment‐naïve patients. All chromosome pairs were arranged in a nonrandom pattern. Chromosomes commonly involved in myeloma‐associated translocations (4 and 14, 14 and 16, 11 and 14) were found in close spatial proximity, and this is correlated with the occurrence of overlapping chromosome territories. The spatial distribution of chromosomes may increase the possibility of chromosomal translocations in multiple myeloma.

Mitogen-induced distinct epialleles are phosphorylated at either H3S10 or H3S28, depending on H3K27 acetylation

Upon mitogenic induction of immediate-early genes, phosphorylation of histone H3 at S10 or S28 occurs on different alleles. S28ph depends on CBP/p300-mediated K27ac, whereas H3 acetylated on K9 by PCAF is phosphorylated on S10. The redundant roles of S10ph and S28ph and their random targeting on distinct alleles may enable a fast response.