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Telomere length dynamics and chromosomal instability in cells derived from telomerase mice.

Hande MP, Samper E, Lansdorp P, Blasco MA - J. Cell Biol. (1999)

Bottom Line: Interestingly, the most frequent fusions found in mTER-/- cells were homologous fusions involving chromosome 2.At various points during the growth of the immortal mTER-/- cells, telomere length was stabilized in a chromosome-specific man-ner.This telomere-maintenance in the absence of telomerase could provide the basis for the ability of mTER-/- cells to grow indefinitely and form tumors.

View Article: PubMed Central - PubMed

Affiliation: Terry Fox Laboratory, British Columbia Cancer Research Center, Vancouver, British Columbia V5Z 1L3, Canada.

ABSTRACT
To study the effect of continued telomere shortening on chromosome stability, we have analyzed the telomere length of two individual chromosomes (chromosomes 2 and 11) in fibroblasts derived from wild-type mice and from mice lacking the mouse telomerase RNA (mTER) gene using quantitative fluorescence in situ hybridization. Telomere length at both chromosomes decreased with increasing generations of mTER-/- mice. At the 6th mouse generation, this telomere shortening resulted in significantly shorter chromosome 2 telomeres than the average telomere length of all chromosomes. Interestingly, the most frequent fusions found in mTER-/- cells were homologous fusions involving chromosome 2. Immortal cultures derived from the primary mTER-/- cells showed a dramatic accumulation of fusions and translocations, revealing that continued growth in the absence of telomerase is a potent inducer of chromosomal instability. Chromosomes 2 and 11 were frequently involved in these abnormalities suggesting that, in the absence of telomerase, chromosomal instability is determined in part by chromosome-specific telomere length. At various points during the growth of the immortal mTER-/- cells, telomere length was stabilized in a chromosome-specific man-ner. This telomere-maintenance in the absence of telomerase could provide the basis for the ability of mTER-/- cells to grow indefinitely and form tumors.

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Examples of the  different end-to-end fusions  detected in mTER−/− cells.  The chromosomal arms involved in the fusion are  inferred by the morphology  of the fused chromosome.  Chromosomes probed with  telomeric PNA to characterize the fusion according to  the presence or absence  of detectable telomeric sequences at the fusion point  are depicted in panels a.  Chromosomes probed with  minor satellite DNA to characterize the fusion according  to the number and location  of centromeres are depicted  in panels b (in p-arm and  p-arm/q-arm fusions). Panels b (in q-arm examples) depict DAPI staining of the  fusion. Panels c depict chromosome painting with whole- chromosome DNA from chromosome 2 (example of type II fusion) and chromosome 11 (examples of type III fusion and p-arm/q-arm fusion). Chromosomes are  counterstained with DAPI for telomere probe and propidium iodide for minor satellite and chromosome probes.
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Figure 4: Examples of the different end-to-end fusions detected in mTER−/− cells. The chromosomal arms involved in the fusion are inferred by the morphology of the fused chromosome. Chromosomes probed with telomeric PNA to characterize the fusion according to the presence or absence of detectable telomeric sequences at the fusion point are depicted in panels a. Chromosomes probed with minor satellite DNA to characterize the fusion according to the number and location of centromeres are depicted in panels b (in p-arm and p-arm/q-arm fusions). Panels b (in q-arm examples) depict DAPI staining of the fusion. Panels c depict chromosome painting with whole- chromosome DNA from chromosome 2 (example of type II fusion) and chromosome 11 (examples of type III fusion and p-arm/q-arm fusion). Chromosomes are counterstained with DAPI for telomere probe and propidium iodide for minor satellite and chromosome probes.

Mentions: To analyze the nature of the chromosomal fusions promoted by the absence of telomerase, we performed FISH on wt and mTER−/− metaphases using telomeric and centromeric probes, as well as chromosomes 2 and 11 painting probes (Materials and Methods). Fig. 4 shows the diagrams of the different fusions characterized in this study together with representative images. End-to-end fusions were classified into different types according to their structure as shown in Fig. 4. Types I, II, and III involve p-to-p arms fusions. Type I fusions contain telomeric repeats at the fusion point (Fig. 4 a) and two copies of minor satellite centromere repeat sequences (b). Type II fusions do not contain detectable telomeric sequences at the fusion point (Fig. 4 a) and yield two centromere signals (b). Type III fusions lack telomeric signals at the fusion point (Fig. 4 a) and only have one centromere signal (b). Type IV and V fusions involve q-to-q arm fusion, and have or lack detectable telomeric signals at the fusion point, respectively. Finally, type VI involves p-to-q arm fusion. In some cases, we performed chromosome painting to determine whether the fusions were homologous (for example, chromosome 2-to-chromosome 2 in panel c of type II fusions) or nonhomologous (for example, chromosome 11 to an undetermined chromosome in panel c of type VI fusions).


Telomere length dynamics and chromosomal instability in cells derived from telomerase mice.

Hande MP, Samper E, Lansdorp P, Blasco MA - J. Cell Biol. (1999)

Examples of the  different end-to-end fusions  detected in mTER−/− cells.  The chromosomal arms involved in the fusion are  inferred by the morphology  of the fused chromosome.  Chromosomes probed with  telomeric PNA to characterize the fusion according to  the presence or absence  of detectable telomeric sequences at the fusion point  are depicted in panels a.  Chromosomes probed with  minor satellite DNA to characterize the fusion according  to the number and location  of centromeres are depicted  in panels b (in p-arm and  p-arm/q-arm fusions). Panels b (in q-arm examples) depict DAPI staining of the  fusion. Panels c depict chromosome painting with whole- chromosome DNA from chromosome 2 (example of type II fusion) and chromosome 11 (examples of type III fusion and p-arm/q-arm fusion). Chromosomes are  counterstained with DAPI for telomere probe and propidium iodide for minor satellite and chromosome probes.
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC2132934&req=5

Figure 4: Examples of the different end-to-end fusions detected in mTER−/− cells. The chromosomal arms involved in the fusion are inferred by the morphology of the fused chromosome. Chromosomes probed with telomeric PNA to characterize the fusion according to the presence or absence of detectable telomeric sequences at the fusion point are depicted in panels a. Chromosomes probed with minor satellite DNA to characterize the fusion according to the number and location of centromeres are depicted in panels b (in p-arm and p-arm/q-arm fusions). Panels b (in q-arm examples) depict DAPI staining of the fusion. Panels c depict chromosome painting with whole- chromosome DNA from chromosome 2 (example of type II fusion) and chromosome 11 (examples of type III fusion and p-arm/q-arm fusion). Chromosomes are counterstained with DAPI for telomere probe and propidium iodide for minor satellite and chromosome probes.
Mentions: To analyze the nature of the chromosomal fusions promoted by the absence of telomerase, we performed FISH on wt and mTER−/− metaphases using telomeric and centromeric probes, as well as chromosomes 2 and 11 painting probes (Materials and Methods). Fig. 4 shows the diagrams of the different fusions characterized in this study together with representative images. End-to-end fusions were classified into different types according to their structure as shown in Fig. 4. Types I, II, and III involve p-to-p arms fusions. Type I fusions contain telomeric repeats at the fusion point (Fig. 4 a) and two copies of minor satellite centromere repeat sequences (b). Type II fusions do not contain detectable telomeric sequences at the fusion point (Fig. 4 a) and yield two centromere signals (b). Type III fusions lack telomeric signals at the fusion point (Fig. 4 a) and only have one centromere signal (b). Type IV and V fusions involve q-to-q arm fusion, and have or lack detectable telomeric signals at the fusion point, respectively. Finally, type VI involves p-to-q arm fusion. In some cases, we performed chromosome painting to determine whether the fusions were homologous (for example, chromosome 2-to-chromosome 2 in panel c of type II fusions) or nonhomologous (for example, chromosome 11 to an undetermined chromosome in panel c of type VI fusions).

Bottom Line: Interestingly, the most frequent fusions found in mTER-/- cells were homologous fusions involving chromosome 2.At various points during the growth of the immortal mTER-/- cells, telomere length was stabilized in a chromosome-specific man-ner.This telomere-maintenance in the absence of telomerase could provide the basis for the ability of mTER-/- cells to grow indefinitely and form tumors.

View Article: PubMed Central - PubMed

Affiliation: Terry Fox Laboratory, British Columbia Cancer Research Center, Vancouver, British Columbia V5Z 1L3, Canada.

ABSTRACT
To study the effect of continued telomere shortening on chromosome stability, we have analyzed the telomere length of two individual chromosomes (chromosomes 2 and 11) in fibroblasts derived from wild-type mice and from mice lacking the mouse telomerase RNA (mTER) gene using quantitative fluorescence in situ hybridization. Telomere length at both chromosomes decreased with increasing generations of mTER-/- mice. At the 6th mouse generation, this telomere shortening resulted in significantly shorter chromosome 2 telomeres than the average telomere length of all chromosomes. Interestingly, the most frequent fusions found in mTER-/- cells were homologous fusions involving chromosome 2. Immortal cultures derived from the primary mTER-/- cells showed a dramatic accumulation of fusions and translocations, revealing that continued growth in the absence of telomerase is a potent inducer of chromosomal instability. Chromosomes 2 and 11 were frequently involved in these abnormalities suggesting that, in the absence of telomerase, chromosomal instability is determined in part by chromosome-specific telomere length. At various points during the growth of the immortal mTER-/- cells, telomere length was stabilized in a chromosome-specific man-ner. This telomere-maintenance in the absence of telomerase could provide the basis for the ability of mTER-/- cells to grow indefinitely and form tumors.

Show MeSH
Related in: MedlinePlus