Change search
ReferencesLink to record
Permanent link

Direct link
Telomerase regulation and telomere dynamics in germinal centers
Umeå University, Faculty of Medicine, Department of Medical Biosciences, Pathology.
Umeå University, Faculty of Medicine, Department of Medical Biosciences, Pathology.
Umeå University, Faculty of Medicine, Department of Medical Biosciences, Pathology.
Show others and affiliations
2001 (English)In: European Journal of Haematology, ISSN 0902-4441, E-ISSN 1600-0609, Vol. 67, no 5-6, 309-317 p.Article in journal (Refereed) Published
Abstract [en]

Telomere length maintenance, usually executed by telomerase, is a prerequisite for an extended or infinite division potential. Nevertheless most telomerase positive normal cells exhibit telomere shortening. This study details the telomerase expression and telomere dynamics in purified tonsil B cell subsets during the germinal center (GC) reaction. Significant telomere lengthening was observed as naive B cells matured to centroblasts and when centroblasts matured further to centrocytes, resulting in an increase in telomere length of about 4 kbp determined by Southern blotting. Immunopurified cell populations were also studied by fluorescence in situ hybridization and flow cytometry (flow-FISH) confirming that the GC B cells exhibited lengthened telomeres. These data were further verified in unpurified tonsil cells by combining flow-FISH and immunophenotyping using selected surface markers. Centroblasts expressed high levels of telomerase activity, which was increased in centrocytes, whereas resting naive, activated naive and memory B cells were telomerase activity negative. Expression levels of the catalytic subunit (hTERT) RNA paralleled the telomerase activity levels. The unique telomere elongation in GC B cells permits extensive proliferation during the GC reaction and provides the memory cells with a substantial increase in division potential. Understanding the telomere biology of GC cells is important in defining requirements for telomere elongation in vivo, with implications for the normal immune system as well as for lymphomas, and could provide insights into how the division potential of cells can be manipulated in vitro.

Place, publisher, year, edition, pages
Blackwell Munksgaard, 2001. Vol. 67, no 5-6, 309-317 p.
Keyword [en]
germinal center, subpopulations, telomerase activity, catalytic subunit, telomere maintenance
National Category
URN: urn:nbn:se:umu:diva-5078DOI: 10.1034/j.1600-0609.2001.00588.xISI: 000173874400005OAI: diva2:144445
Available from: 2003-06-26 Created: 2003-06-26 Last updated: 2014-04-25Bibliographically approved
In thesis
1. Telomere analysis of normal and neoplastic hematopoietic cells: studies focusing on fluorescence in situ hybridization and flow cytometry
Open this publication in new window or tab >>Telomere analysis of normal and neoplastic hematopoietic cells: studies focusing on fluorescence in situ hybridization and flow cytometry
2003 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

The telomeres are specialized structures at the end of the chromosomes composed of the repeated DNA sequence (TTAGGG)n and specific proteins bound to the DNA. The telomeres protect the chromosomes from degradation and end to end fusions. Due to the end-replication problem, the telomeric DNA shortens every cell division, forcing the cells into senescence at a critical telomere length. This process can be counteracted by activating a specialized enzyme, telomerase, which adds telomeric repeats to the chromosome ends leading to an extended or infinite cellular life span. Telomerase activity is absent in most somatic tissues but is found in germ cells, stem cells, activated lymphocytes and the vast majority of tumor cells and permanent cell lines. Hence, telomerase has been suggested as a target for cancer treatment as malignant cells almost exclusively express the enzyme and in that context telomere length measurements will be of great importance.

Telomere length is traditionally measured with a Southern blot based technique. A new method for telomere analysis of cells in suspension, called flow-FISH, was developed based on fluorescence in situ hybridization using a telomeric peptide nucleic acid (PNA) probe,

DNA staining with propidium iodide and quantification by flow cytometry. Flow-FISH had high reproducibility and the telomere length measurements showed good correlation with Southern blotting results. The flow-FISH technique also allows studies of cells in specific phases of the cell cycle and the replication timing of telomeric, centromeric and other repetitive sequences were analyzed in a number of cells. Like previous studies, centromeres were shown to replicate late in S phase while the telomere repeats were found to replicate early in S phase or concomitant with the bulk DNA, which is opposite to the patterns described in yeast.

In benign immunopurified lymphocytes from tonsils, high telomerase activity was found in germinal center (GC) B cells. This population also had high hTERT mRNA levels and displayed a telomere elongation as shown by flow-FISH and Southern blotting. Combined immunophenotyping and flow-FISH on unpurified tonsil cells confirmed the results.

Chronic lymphocytic leukemia (CLL), the most common leukemia in adults, can be divided into pre-GC CLL, characterized by unmutated immunoglobulin VH genes and worse prognosis, and post-GC CLL, with mutated VH genes and better prognosis. In 61 cases of CLL, telomere length was measured with Southern blotting and VH gene mutation status was analyzed. A new association was found between VH mutation status and telomere length, where cases with longer telomeres and mutated VH genes (post-GC CLL) had better prognosis

than CLL with short telomeres and unmutated VH genes (pre-GC CLL). A larger study of 112 CLL cases was performed using flow-FISH. The same correlation between telomere length and VH mutation status was found but gender seemed to be of importance as telomere length was a significant prognostic factor for the male CLL patients but not in the female group. Age of the patients and spread of disease seemed to affect the prognostic value of VH gene mutation status.

Place, publisher, year, edition, pages
Umeå: Medicinsk biovetenskap, 2003. 66 p.
Umeå University medical dissertations, ISSN 0346-6612 ; 840
Biomedicine, telomere, telomerase, fluorescence in situ hybridization, flow cytometry, flow-FISH, replication timing, chronic lymphocytic leukemia, immunoglobulin gene, prognosis, Biomedicin
National Category
Microbiology in the medical area
Research subject
Medical Cell Biology
urn:nbn:se:umu:diva-76 (URN)91-7305-444-5 (ISBN)
Public defence
2003-05-23, Betula, 6M, Umeå, 09:00
Available from: 2003-06-26 Created: 2003-06-26Bibliographically approved

Open Access in DiVA

No full text

Other links

Publisher's full text

Search in DiVA

By author/editor
Norrback, Karl-FredrikHultdin, MagnusOsterman, PiaRoos, Göran
By organisation
In the same journal
European Journal of Haematology

Search outside of DiVA

GoogleGoogle Scholar
The number of downloads is the sum of all downloads of full texts. It may include eg previous versions that are now no longer available

Altmetric score

Total: 69 hits
ReferencesLink to record
Permanent link

Direct link