Telomere Length Dynamics and Chromosomal Instability in Cells Derived from Telomerase Null Mice

“Indeed, telomere shortening to a critical length has been proposed to limit the life span of somatic cells in humans (Harley et al., 1990; Counter et al., 1992).”

“It has been recently shown that the introduction of the telomerase catalytic subunit in primary human cells is sufficient to restore enzymatic activity, to elongate and maintain telomeres, and, in some cell types, to sustain immortal growth ( Bodnar et al., 1998; Wang et al., 1998; Kiyono et al., 1998).”

“In such cells the enzyme telomerase seems to be the main mechanism for the maintenance of telomere length (Greider and Blackburn, 1985; Morin, 1989; Yu et al., 1990; Singer and Gottschling, 1994; McEachern and Blackburn, 1996; Nakamura et al., 1997).”

“These mechanisms, which can be either telomerase dependent (reviewed in Shay and Bacchetti, 1997 ) or independent (this paper and Bryan et al., 1995, 1997), can prevent telomeres from further shortening, allowing the immortal growth of cells that have critically short telomeres and a high degree of genetic instability.”

“col (Todaro and Green, 1963) in dishes of 10 cm diam, seeding 10 6 cells ev-”

“, 1998), an RNA molecule that contains the template for the synthesis of telomeric repeats (Greider and Blackburn, 1989; Singer and Gottschling, 1994; Blasco et al., 1995; Feng et al., 1995; McEachern and Blackburn, 1995), and other associated proteins (Collins et al.”

“The details are explained elsewhere (Blasco et al., 1997).”

“Indeed, telomere shortening to a critical length has been proposed to limit the life span of somatic cells in humans (Harley et al., 1990; Counter et al., 1992).”

“…by a protein catalytic subunit with similarity to other reverse transcriptases (Lingner et al., 1997; Harrington et al., 1997a; Kilian et al., 1997; Meyerson et al., 1997; Nakamura et al., 1997; MartínAddress correspondence to María A. Blasco, Department of Immunology and Oncology, Centro Nacional…”

“It has been shown recently that telomere binding proteins are of crucial importance to prevent end-to-end fusions in human chromosomes ( Van Steensel et al., 1998 ).”

“, 1998), an RNA molecule that contains the template for the synthesis of telomeric repeats (Greider and Blackburn, 1989; Singer and Gottschling, 1994; Blasco et al., 1995; Feng et al., 1995; McEachern and Blackburn, 1995), and other associated proteins (Collins et al.”

“In such cells the enzyme telomerase seems to be the main mechanism for the maintenance of telomere length (Greider and Blackburn, 1985; Morin, 1989; Yu et al., 1990; Singer and Gottschling, 1994; McEachern and Blackburn, 1996; Nakamura et al., 1997).”

“Greider, C.W., and E.H. Blackburn.”

“Such variation between littermates could be the basis for the fact that only a percentage of KO-G6 mice show defects associated with telomere loss (Lee et al., 1998; Herrera el al., 1999).”

“Telomerase is formed by a protein catalytic subunit with similarity to other reverse transcriptases (Lingner et al., 1997; Harrington et al., 1997a; Kilian et al., 1997; Meyerson et al., 1997; Nakamura et al., 1997; MartínAddress correspondence to María A. Blasco, Department of Immunology and…”

“…been recently shown that the introduction of the telomerase catalytic subunit in primary human cells is sufficient to restore enzymatic activity, to elongate and maintain telomeres, and, in some cell types, to sustain immortal growth (Bodnar et al., 1998; Wang et al., 1998; Kiyono et al., 1998).”

“Telomerase is a reverse transcriptase that elongates telomeres by synthesizing TTAGGG repeats onto the 3 9 ends of chromosomes.”

“Interestingly, it is possible to isolate survivor yeast strains that are able to stabilize their chromosomes by mechanisms that involve telomere elongation by recombination or chromosome circularization (Lundblad and Blackburn, 1993; McEachern and Blackburn, 1996; Nakamura et al., 1997, 1998; Naito et al., 1998).”

“These specialized structures constitute the final 10 kb of all human chromosomes, and the final 12–80 kb of all mouse chromosomes (Lansdorp et al., 1996; Zijlmans et al., 1997).”

“Recent studies in yeast and mice have proven that telomeres are essential to maintain chromosomal stability (Sandell and Zakian, 1993; Blasco et al., 1997; Lee et al., 1998; Naito et al., 1998; Nakamura et al., 1998).”

“, 1998), an RNA molecule that contains the template for the synthesis of telomeric repeats (Greider and Blackburn, 1989; Singer and Gottschling, 1994; Blasco et al., 1995; Feng et al., 1995; McEachern and Blackburn, 1995), and other associated proteins (Collins et al.”

“…for the synthesis of telomeric repeats (Greider and Blackburn, 1989; Singer and Gottschling, 1994; Blasco et al., 1995; Feng et al., 1995; McEachern and Blackburn, 1995), and other associated proteins (Collins et al., 1995; Harrington et al., 1997b; Nakayama et al., 1997; Gandhi and Collins, 1998).”

“…been recently shown that the introduction of the telomerase catalytic subunit in primary human cells is sufficient to restore enzymatic activity, to elongate and maintain telomeres, and, in some cell types, to sustain immortal growth (Bodnar et al., 1998; Wang et al., 1998; Kiyono et al., 1998).”

“In such cells the enzyme telomerase seems to be the main mechanism for the maintenance of telomere length (Greider and Blackburn, 1985; Morin, 1989; Yu et al., 1990; Singer and Gottschling, 1994; McEachern and Blackburn, 1996; Nakamura et al., 1997).”

“Telomerase is formed by a protein catalytic subunit with similarity to other reverse transcriptases (Lingner et al., 1997; Harrington et al., 1997a; Kilian et al., 1997; Meyerson et al., 1997; Nakamura et al., 1997; MartínAddress correspondence to María A. Blasco, Department of Immunology and…”

“The loss of control of the chromosomal number or aneuploidy is an alteration commonly observed in cultured cells (Zindy et al., 1997).”

“FISH with Cy-3 labeled (CCCTAA) 3 peptidenucleic acid, and subsequent quantitative analysis of digital images were performed as described (Zijlmans et al., 1997).”

“, Rad 52 (McEachern and Blackburn, 1996) or in DNA repair, such as DNA-PK, ATM, Rad 3, tel11, and TEL 1, have been proposed as candidates because their mutation results in accelerated loss of telomeres (Greenwell et al., 1995; Boulton and Jackson, 1996; Metcalfe et al., 1996; Nugent et al., 1998; Naito et al., 1998).”

“…for the synthesis of telomeric repeats (Greider and Blackburn, 1989; Singer and Gottschling, 1994; Blasco et al., 1995; Feng et al., 1995; McEachern and Blackburn, 1995), and other associated proteins (Collins et al., 1995; Harrington et al., 1997b; Nakayama et al., 1997; Gandhi and Collins, 1998).”

“The Journal of Cell Biology, Volume 144, 1999 594 ficient to prevent telomere erosion as it has been proposed previously for other cell types (Counter et al., 1994; Chiu et al., 1996) or, alternatively, that telomere length in these cultured cells is not tightly regulated around a fixed length.”

“…and Blackburn, 1996) or in DNA repair, such as DNA-PK, ATM, Rad 3, tel11, and TEL 1, have been proposed as candidates because their mutation results in accelerated loss of telomeres (Greenwell et al., 1995; Boulton and Jackson, 1996; Metcalfe et al., 1996; Nugent et al., 1998; Naito et al., 1998).”

“…for the synthesis of telomeric repeats (Greider and Blackburn, 1989; Singer and Gottschling, 1994; Blasco et al., 1995; Feng et al., 1995; McEachern and Blackburn, 1995), and other associated proteins (Collins et al., 1995; Harrington et al., 1997b; Nakayama et al., 1997; Gandhi and Collins, 1998).”

“…and Blackburn, 1996) or in DNA repair, such as DNA-PK, ATM, Rad 3, tel11, and TEL 1, have been proposed as candidates because their mutation results in accelerated loss of telomeres (Greenwell et al., 1995; Boulton and Jackson, 1996; Metcalfe et al., 1996; Nugent et al., 1998; Naito et al., 1998).”

“, 1998), an RNA molecule that contains the template for the synthesis of telomeric repeats (Greider and Blackburn, 1989; Singer and Gottschling, 1994; Blasco et al., 1995; Feng et al., 1995; McEachern and Blackburn, 1995), and other associated proteins (Collins et al.”

“The Journal of Cell Biology, Volume 144, 1999 594 ficient to prevent telomere erosion as it has been proposed previously for other cell types (Counter et al., 1994; Chiu et al., 1996) or, alternatively, that telomere length in these cultured cells is not tightly regulated around a fixed length.”

“…and Blackburn, 1996) or in DNA repair, such as DNA-PK, ATM, Rad 3, tel11, and TEL 1, have been proposed as candidates because their mutation results in accelerated loss of telomeres (Greenwell et al., 1995; Boulton and Jackson, 1996; Metcalfe et al., 1996; Nugent et al., 1998; Naito et al., 1998).”

“, 1998), an RNA molecule that contains the template for the synthesis of telomeric repeats (Greider and Blackburn, 1989; Singer and Gottschling, 1994; Blasco et al., 1995; Feng et al., 1995; McEachern and Blackburn, 1995), and other associated proteins (Collins et al.”

“Similarly, other studies have suggested a role of telomeres and telomere binding proteins in chromosome segregation and meiosis (Bass et al., 1997; Chikashige et al., 1997; Chua et al., 1997; Conrad et al., 1997, Cooper et al., 1998; Naito et al., 1998).”

“Recent studies in yeast and mice have proven that telomeres are essential to maintain chromosomal stability (Sandell and Zakian, 1993; Blasco et al., 1997; Lee et al., 1998; Naito et al., 1998; Nakamura et al., 1998).”

“Similarly, other studies have suggested a role of telomeres and telomere binding proteins in chromosome segregation and meiosis (Bass et al., 1997; Chikashige et al., 1997; Chua et al., 1997; Conrad et al., 1997, Cooper et al., 1998; Naito et al., 1998).”

“…for the synthesis of telomeric repeats (Greider and Blackburn, 1989; Singer and Gottschling, 1994; Blasco et al., 1995; Feng et al., 1995; McEachern and Blackburn, 1995), and other associated proteins (Collins et al., 1995; Harrington et al., 1997b; Nakayama et al., 1997; Gandhi and Collins, 1998).”

“, Rad 52 (McEachern and Blackburn, 1996) or in DNA repair, such as DNA-PK, ATM, Rad 3, tel11, and TEL 1, have been proposed as candidates because their mutation results in accelerated loss of telomeres (Greenwell et al., 1995; Boulton and Jackson, 1996; Metcalfe et al., 1996; Nugent et al., 1998; Naito et al., 1998).”

“Interestingly, it is possible to isolate survivor yeast strains that are able to stabilize their chromosomes by mechanisms that involve telomere elongation by recombination or chromosome circularization (Lundblad and Blackburn, 1993; McEachern and Blackburn, 1996; Nakamura et al., 1997, 1998; Naito et al., 1998).”

“In addition, the study of Tetrahymena mutants with an altered telomerase RNA template suggests an important role of telomeres in chromatid separation during anaphase (Kirk et al., 1997).”

“Similarly, other studies have suggested a role of telomeres and telomere binding proteins in chromosome segregation and meiosis (Bass et al., 1997; Chikashige et al., 1997; Chua et al., 1997; Conrad et al., 1997, Cooper et al., 1998; Naito et al., 1998).”

“Moreover, there are a variety of human established cell lines that do not show detectable telomerase activity ( Bryan et al., 1995, 1997 ).”

“Similarly, other studies have suggested a role of telomeres and telomere binding proteins in chromosome segregation and meiosis (Bass et al., 1997; Chikashige et al., 1997; Chua et al., 1997; Conrad et al., 1997, Cooper et al., 1998; Naito et al., 1998).”

“300 divisions, suggesting that the growth of ES cells is telomerase dependent (Niida et al., 1998).”

“This variation in telomere length could be the basis for the variable penetrance of the phenotypes described in 6th generation mTER 2 / 2 mice (Lee et al., 1998; Herrera et al., 1999).”

“The hybridization was performed as described (Hande et al., 1996).”

“, 1995; McEachern and Blackburn, 1995), and other associated proteins (Collins et al., 1995; Harrington et al., 1997b; Nakayama et al., 1997; Gandhi and Collins, 1998).”

“Q-FISH has become the method of choice for the analysis of telomere length in the mouse (Lansdorp, 1997) and for further details the reader is referred to the references above.”

“Here we find that ditions (Hande et al., 1999). the ability of the mTR2/2 mice to respond to various physiological stresses is compromised and declines Progressive Increase in the Rate of Spontaneous with increasing age of the mouse.”

“) mTRϪ/Ϫ mice (Table 1) (Blasco et al., 1997; Hemann et al., 2001b; Lee et al., 1998).”

“The technique is well established to study telomere biology in many settings (8, 81).”

“In addition, our finding that mTR −/− MEFs do not senesce in 3% oxygen, in contrast to telomerase-negative human cells, is most probably caused by the ability of mouse chromosomes to stabilize telomeres in the absence of telomerase until alternative telomere maintenance pathways are induce”