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Impact of telomerase ablation on organismal viability, aging, and tumorigenesis in mice lacking the DNA repair proteins PARP-1, Ku86, or DNA-PKcs.

Espejel S, Klatt P, Ménissier-de Murcia J, Martín-Caballero J, Flores JM, Taccioli G, de Murcia G, Blasco MA - J. Cell Biol. (2004)

Bottom Line: First, we show that abrogation of PARP-1 in the absence of telomerase does not affect the rate of telomere shortening, telomere capping, or organismal viability compared with single telomerase-deficient controls.In contrast, mice doubly deficient for telomerase and either Ku86 or DNA-PKcs manifest accelerated loss of organismal viability compared with single telomerase-deficient mice.These results support the notion that absence of telomerase and short telomeres in combination with DNA repair deficiencies accelerate the aging process without impacting on tumorigenesis.

View Article: PubMed Central - PubMed

Affiliation: Molecular Oncology Program, Spanish National Cancer Center (CNIO), E-28029 Madrid, Spain.

ABSTRACT
The DNA repair proteins poly(ADP-ribose) polymerase-1 (PARP-1), Ku86, and catalytic subunit of DNA-PK (DNA-PKcs) have been involved in telomere metabolism. To genetically dissect the impact of these activities on telomere function, as well as organismal cancer and aging, we have generated mice doubly deficient for both telomerase and any of the mentioned DNA repair proteins, PARP-1, Ku86, or DNA-PKcs. First, we show that abrogation of PARP-1 in the absence of telomerase does not affect the rate of telomere shortening, telomere capping, or organismal viability compared with single telomerase-deficient controls. Thus, PARP-1 does not have a major role in telomere metabolism, not even in the context of telomerase deficiency. In contrast, mice doubly deficient for telomerase and either Ku86 or DNA-PKcs manifest accelerated loss of organismal viability compared with single telomerase-deficient mice. Interestingly, this loss of organismal viability correlates with proliferative defects and age-related pathologies, but not with increased incidence of cancer. These results support the notion that absence of telomerase and short telomeres in combination with DNA repair deficiencies accelerate the aging process without impacting on tumorigenesis.

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Effect of Ku86, DNA-PKcs, or PARP-1 deficiency on the early onset of age-related pathologies in successive generations of telomerase-deficient mice. Mice with telomerase (Terc+/+) and four successive generations of telomerase-deficient (Terc−/−) mice (G1–G4) that were either wild-type (gray bars) or deficient (black bars) for Ku86 (A), DNA-PKcs (B), and PARP-1 (C) were killed when they showed signs of poor health and analyzed for the occurrence of a variety of age-associated pathologies (see Table S1, available at http://www.jcb.org/cgi/content/full/jcb.200407178/DC1). Here, we show the onset of these aging-associated pathologies in animals younger than 1 yr of age in a given mouse group relative to the total number of detected pathologies in that group. The number of senile lesions detected in young animals (<1 yr) in relation to the total number of lesions detected in the respective mouse group is given above each bar; for example, as shown in A, in the Terc+/+/Ku86−/− mouse cohort we detected a total of 21 senile lesions and 11 of them were detected in mice younger than 1 yr of age. Significant differences (P < 0.05, Fisher's exact test) between single and double mutant animals are indicated by an asterisk; n.a. = not analyzed.
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fig5: Effect of Ku86, DNA-PKcs, or PARP-1 deficiency on the early onset of age-related pathologies in successive generations of telomerase-deficient mice. Mice with telomerase (Terc+/+) and four successive generations of telomerase-deficient (Terc−/−) mice (G1–G4) that were either wild-type (gray bars) or deficient (black bars) for Ku86 (A), DNA-PKcs (B), and PARP-1 (C) were killed when they showed signs of poor health and analyzed for the occurrence of a variety of age-associated pathologies (see Table S1, available at http://www.jcb.org/cgi/content/full/jcb.200407178/DC1). Here, we show the onset of these aging-associated pathologies in animals younger than 1 yr of age in a given mouse group relative to the total number of detected pathologies in that group. The number of senile lesions detected in young animals (<1 yr) in relation to the total number of lesions detected in the respective mouse group is given above each bar; for example, as shown in A, in the Terc+/+/Ku86−/− mouse cohort we detected a total of 21 senile lesions and 11 of them were detected in mice younger than 1 yr of age. Significant differences (P < 0.05, Fisher's exact test) between single and double mutant animals are indicated by an asterisk; n.a. = not analyzed.

Mentions: The observed relationship between chronological age and mortality (Fig. 2), as well as the frequent occurrence of proliferative defects (Fig. 3) in double mutant mice indicate a genetic interaction between telomerase and DNA repair proteins in longevity. To further study whether telomere shortening cooperates with loss of Ku86, DNA-PKcs, or PARP-1 to accelerate the aging process, we studied the age distribution of age-related pathologies detected in moribund animals (see Materials and methods; Online supplemental material for detailed list of pathologies). With the exception of intestinal and testicular atrophy (Fig. 3), the incidence of any individual pathology was not significantly altered when comparing different genotypes and/or different generations of Terc-deficient animals (see Online supplemental material). Thus, to get an insight into the overall organismal fitness of these animals as a function of their age, we calculated the onset of aging-associated pathologies at <1 yr of age in a given mouse group relative to the total number of pathologies detected in this group; for example, in Terc+/+/Ku86−/− cohorts we detected a total of 21 senile lesions (see Online supplemental material), and 11 of them were detected in animals at < 1 yr of age (Fig. 5 A). In this way, we obtained a more comprehensive measure for the relative incidence of senile lesions in young animals (<1 yr of age) either of the wild type or deficient for Ku86, DNA-PKcs, or PARP-1 along successive generations of telomerase deficiency (Fig. 5). Concurring with our previous observations (Herrera et al., 1999), we found an association of progressive telomere shortening with symptoms of premature aging. Although we did not observe any senile lesion in wild-type animals at <1 yr of age (0%), progressive telomere shortening incremented the incidence of such pathologies to 8% in G1 (P = 0.5), 1% in G2 (P = 0.9), 14% in G3 (P = 0.2), and to 38% in late-generation G4-Terc−/− animals (P = 0.01) (Fig. 5 A, gray bars). In the presence of telomerase, ablation of Ku86 caused a high incidence of senile lesions in young animals (52%), but progressive exhaustion of telomeres further exacerbated this premature aging phenotype with 68, 92, 100, and 100% of senescence-associated pathologies detected in young animals from G1 (P = 0.1), G2 (P < 0.001), and late generation G3 (P < 0.01) and G4 (P = 0.2) Terc−/− cohorts, respectively (Fig. 5 A, black bars). The cooperative impact of telomerase ablation and Ku86 deficiency on the premature occurrence of age-related pathologies was also evident from a comparison of Ku86-deficient cohorts with their respective wild-type littermates in G1 (P < 0.001), G2 (P < 0.001), G3 (P < 0.001), and G4 (P = 0.06) (Fig. 5 A, black bars versus gray bars).


Impact of telomerase ablation on organismal viability, aging, and tumorigenesis in mice lacking the DNA repair proteins PARP-1, Ku86, or DNA-PKcs.

Espejel S, Klatt P, Ménissier-de Murcia J, Martín-Caballero J, Flores JM, Taccioli G, de Murcia G, Blasco MA - J. Cell Biol. (2004)

Effect of Ku86, DNA-PKcs, or PARP-1 deficiency on the early onset of age-related pathologies in successive generations of telomerase-deficient mice. Mice with telomerase (Terc+/+) and four successive generations of telomerase-deficient (Terc−/−) mice (G1–G4) that were either wild-type (gray bars) or deficient (black bars) for Ku86 (A), DNA-PKcs (B), and PARP-1 (C) were killed when they showed signs of poor health and analyzed for the occurrence of a variety of age-associated pathologies (see Table S1, available at http://www.jcb.org/cgi/content/full/jcb.200407178/DC1). Here, we show the onset of these aging-associated pathologies in animals younger than 1 yr of age in a given mouse group relative to the total number of detected pathologies in that group. The number of senile lesions detected in young animals (<1 yr) in relation to the total number of lesions detected in the respective mouse group is given above each bar; for example, as shown in A, in the Terc+/+/Ku86−/− mouse cohort we detected a total of 21 senile lesions and 11 of them were detected in mice younger than 1 yr of age. Significant differences (P < 0.05, Fisher's exact test) between single and double mutant animals are indicated by an asterisk; n.a. = not analyzed.
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
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fig5: Effect of Ku86, DNA-PKcs, or PARP-1 deficiency on the early onset of age-related pathologies in successive generations of telomerase-deficient mice. Mice with telomerase (Terc+/+) and four successive generations of telomerase-deficient (Terc−/−) mice (G1–G4) that were either wild-type (gray bars) or deficient (black bars) for Ku86 (A), DNA-PKcs (B), and PARP-1 (C) were killed when they showed signs of poor health and analyzed for the occurrence of a variety of age-associated pathologies (see Table S1, available at http://www.jcb.org/cgi/content/full/jcb.200407178/DC1). Here, we show the onset of these aging-associated pathologies in animals younger than 1 yr of age in a given mouse group relative to the total number of detected pathologies in that group. The number of senile lesions detected in young animals (<1 yr) in relation to the total number of lesions detected in the respective mouse group is given above each bar; for example, as shown in A, in the Terc+/+/Ku86−/− mouse cohort we detected a total of 21 senile lesions and 11 of them were detected in mice younger than 1 yr of age. Significant differences (P < 0.05, Fisher's exact test) between single and double mutant animals are indicated by an asterisk; n.a. = not analyzed.
Mentions: The observed relationship between chronological age and mortality (Fig. 2), as well as the frequent occurrence of proliferative defects (Fig. 3) in double mutant mice indicate a genetic interaction between telomerase and DNA repair proteins in longevity. To further study whether telomere shortening cooperates with loss of Ku86, DNA-PKcs, or PARP-1 to accelerate the aging process, we studied the age distribution of age-related pathologies detected in moribund animals (see Materials and methods; Online supplemental material for detailed list of pathologies). With the exception of intestinal and testicular atrophy (Fig. 3), the incidence of any individual pathology was not significantly altered when comparing different genotypes and/or different generations of Terc-deficient animals (see Online supplemental material). Thus, to get an insight into the overall organismal fitness of these animals as a function of their age, we calculated the onset of aging-associated pathologies at <1 yr of age in a given mouse group relative to the total number of pathologies detected in this group; for example, in Terc+/+/Ku86−/− cohorts we detected a total of 21 senile lesions (see Online supplemental material), and 11 of them were detected in animals at < 1 yr of age (Fig. 5 A). In this way, we obtained a more comprehensive measure for the relative incidence of senile lesions in young animals (<1 yr of age) either of the wild type or deficient for Ku86, DNA-PKcs, or PARP-1 along successive generations of telomerase deficiency (Fig. 5). Concurring with our previous observations (Herrera et al., 1999), we found an association of progressive telomere shortening with symptoms of premature aging. Although we did not observe any senile lesion in wild-type animals at <1 yr of age (0%), progressive telomere shortening incremented the incidence of such pathologies to 8% in G1 (P = 0.5), 1% in G2 (P = 0.9), 14% in G3 (P = 0.2), and to 38% in late-generation G4-Terc−/− animals (P = 0.01) (Fig. 5 A, gray bars). In the presence of telomerase, ablation of Ku86 caused a high incidence of senile lesions in young animals (52%), but progressive exhaustion of telomeres further exacerbated this premature aging phenotype with 68, 92, 100, and 100% of senescence-associated pathologies detected in young animals from G1 (P = 0.1), G2 (P < 0.001), and late generation G3 (P < 0.01) and G4 (P = 0.2) Terc−/− cohorts, respectively (Fig. 5 A, black bars). The cooperative impact of telomerase ablation and Ku86 deficiency on the premature occurrence of age-related pathologies was also evident from a comparison of Ku86-deficient cohorts with their respective wild-type littermates in G1 (P < 0.001), G2 (P < 0.001), G3 (P < 0.001), and G4 (P = 0.06) (Fig. 5 A, black bars versus gray bars).

Bottom Line: First, we show that abrogation of PARP-1 in the absence of telomerase does not affect the rate of telomere shortening, telomere capping, or organismal viability compared with single telomerase-deficient controls.In contrast, mice doubly deficient for telomerase and either Ku86 or DNA-PKcs manifest accelerated loss of organismal viability compared with single telomerase-deficient mice.These results support the notion that absence of telomerase and short telomeres in combination with DNA repair deficiencies accelerate the aging process without impacting on tumorigenesis.

View Article: PubMed Central - PubMed

Affiliation: Molecular Oncology Program, Spanish National Cancer Center (CNIO), E-28029 Madrid, Spain.

ABSTRACT
The DNA repair proteins poly(ADP-ribose) polymerase-1 (PARP-1), Ku86, and catalytic subunit of DNA-PK (DNA-PKcs) have been involved in telomere metabolism. To genetically dissect the impact of these activities on telomere function, as well as organismal cancer and aging, we have generated mice doubly deficient for both telomerase and any of the mentioned DNA repair proteins, PARP-1, Ku86, or DNA-PKcs. First, we show that abrogation of PARP-1 in the absence of telomerase does not affect the rate of telomere shortening, telomere capping, or organismal viability compared with single telomerase-deficient controls. Thus, PARP-1 does not have a major role in telomere metabolism, not even in the context of telomerase deficiency. In contrast, mice doubly deficient for telomerase and either Ku86 or DNA-PKcs manifest accelerated loss of organismal viability compared with single telomerase-deficient mice. Interestingly, this loss of organismal viability correlates with proliferative defects and age-related pathologies, but not with increased incidence of cancer. These results support the notion that absence of telomerase and short telomeres in combination with DNA repair deficiencies accelerate the aging process without impacting on tumorigenesis.

Show MeSH
Related in: MedlinePlus