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Telomeres cluster de novo before the initiation of synapsis: a three-dimensional spatial analysis of telomere positions before and during meiotic prophase.

Bass HW, Marshall WF, Sedat JW, Agard DA, Cande WZ - J. Cell Biol. (1997)

Bottom Line: We found that nuclei at the last somatic prophase before meiosis exhibit a nonrandom, polarized chromosome organization resulting in a loose grouping of telomeres.The stage-dependent changes in telomere arrangements are suggestive of specific, active telomere-associated motility processes with meiotic functions.Thus, the formation of the cluster itself is an early event in the nuclear reorganizations associated with meiosis and may reflect a control point in the initiation of synapsis or crossing over.

View Article: PubMed Central - PubMed

Affiliation: Department of Molecular and Cell Biology, University of California at Berkeley 94720, USA.

ABSTRACT
We have analyzed the progressive changes in the spatial distribution of telomeres during meiosis using three-dimensional, high resolution fluorescence microscopy. Fixed meiotic cells of maize (Zea mays L.) were subjected to in situ hybridization under conditions that preserved chromosome structure, allowing identification of stage-dependent changes in telomere arrangements. We found that nuclei at the last somatic prophase before meiosis exhibit a nonrandom, polarized chromosome organization resulting in a loose grouping of telomeres. Quantitative measurements on the spatial arrangements of telomeres revealed that, as cells passed through premeiotic interphase and into leptotene, there was an increase in the frequency of large telomere-to-telomere distances and a decrease in the bias toward peripheral localization of telomeres. By leptotene, there was no obvious evidence of telomere grouping, and the large, singular nucleolus was internally located, nearly concentric with the nucleus. At the end of leptotene, telomeres clustered de novo at the nuclear periphery, coincident with a displacement of the nucleolus to one side. The telomere cluster persisted throughout zygotene and into early pachytene. The nucleolus was adjacent to the cluster at zygotene. At the pachytene stage, telomeres rearranged again by dispersing throughout the nuclear periphery. The stage-dependent changes in telomere arrangements are suggestive of specific, active telomere-associated motility processes with meiotic functions. Thus, the formation of the cluster itself is an early event in the nuclear reorganizations associated with meiosis and may reflect a control point in the initiation of synapsis or crossing over.

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Specificity of oligonucleotide telomere FISH. A partially ruptured and flattened pachytene nucleus following FISH with telomere oligonucleotide probe (see Materials and Methods). Images show the relationship of chromosomes (A, DAPI image) and telomeres signals (B, FITC image), by two-colored overlay (C) with inset enlargement. The nucleolus (n) and some telomeres (t) are indicated. Bars: (A) 5 μm; (inset) 1 μm.
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Figure 2: Specificity of oligonucleotide telomere FISH. A partially ruptured and flattened pachytene nucleus following FISH with telomere oligonucleotide probe (see Materials and Methods). Images show the relationship of chromosomes (A, DAPI image) and telomeres signals (B, FITC image), by two-colored overlay (C) with inset enlargement. The nucleolus (n) and some telomeres (t) are indicated. Bars: (A) 5 μm; (inset) 1 μm.

Mentions: Individual nuclei were modeled using the Priism software program 3DModel (8). Each model file contains a list of points with the real-space coordinates of three objects: the edge of the nucleus (Object-1), the edge of the nucleolus (Object-2), and the telomeres (all the points in Object-3). Negative control experiments were carried out to confirm that none of the bright spots identified as telomeres could be explained as nonspecific background artifacts. An FITC-labeled oligonucleotide probe (produced as described above) homologous to the noncoding strand of a single copy maize gene was used under standard conditions (see above). The resulting FITC images lacked bright dots, but exhibited nucleolar staining similar to the nonspecific background staining seen with the telomere probe (see Fig. 2 B). In this study, we have decided to define telomeres as the discrete spots (three to six pixels across in the X and Y dimensions) in the FISHtreated nuclei. We also required that these spots be brighter (by a factor of > 1.5-fold) than the average intensity of pixels in the nucleolus, and within or touching the DAPI-revealed chromatin of the nucleus. These criteria allowed us to identify telomeres in decondensed chromatin where the DAPI images provide little to no assistance in recognizing the ends of chromosomes. Typically, 30–80% of the expected telomeres were observed.


Telomeres cluster de novo before the initiation of synapsis: a three-dimensional spatial analysis of telomere positions before and during meiotic prophase.

Bass HW, Marshall WF, Sedat JW, Agard DA, Cande WZ - J. Cell Biol. (1997)

Specificity of oligonucleotide telomere FISH. A partially ruptured and flattened pachytene nucleus following FISH with telomere oligonucleotide probe (see Materials and Methods). Images show the relationship of chromosomes (A, DAPI image) and telomeres signals (B, FITC image), by two-colored overlay (C) with inset enlargement. The nucleolus (n) and some telomeres (t) are indicated. Bars: (A) 5 μm; (inset) 1 μm.
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC2139864&req=5

Figure 2: Specificity of oligonucleotide telomere FISH. A partially ruptured and flattened pachytene nucleus following FISH with telomere oligonucleotide probe (see Materials and Methods). Images show the relationship of chromosomes (A, DAPI image) and telomeres signals (B, FITC image), by two-colored overlay (C) with inset enlargement. The nucleolus (n) and some telomeres (t) are indicated. Bars: (A) 5 μm; (inset) 1 μm.
Mentions: Individual nuclei were modeled using the Priism software program 3DModel (8). Each model file contains a list of points with the real-space coordinates of three objects: the edge of the nucleus (Object-1), the edge of the nucleolus (Object-2), and the telomeres (all the points in Object-3). Negative control experiments were carried out to confirm that none of the bright spots identified as telomeres could be explained as nonspecific background artifacts. An FITC-labeled oligonucleotide probe (produced as described above) homologous to the noncoding strand of a single copy maize gene was used under standard conditions (see above). The resulting FITC images lacked bright dots, but exhibited nucleolar staining similar to the nonspecific background staining seen with the telomere probe (see Fig. 2 B). In this study, we have decided to define telomeres as the discrete spots (three to six pixels across in the X and Y dimensions) in the FISHtreated nuclei. We also required that these spots be brighter (by a factor of > 1.5-fold) than the average intensity of pixels in the nucleolus, and within or touching the DAPI-revealed chromatin of the nucleus. These criteria allowed us to identify telomeres in decondensed chromatin where the DAPI images provide little to no assistance in recognizing the ends of chromosomes. Typically, 30–80% of the expected telomeres were observed.

Bottom Line: We found that nuclei at the last somatic prophase before meiosis exhibit a nonrandom, polarized chromosome organization resulting in a loose grouping of telomeres.The stage-dependent changes in telomere arrangements are suggestive of specific, active telomere-associated motility processes with meiotic functions.Thus, the formation of the cluster itself is an early event in the nuclear reorganizations associated with meiosis and may reflect a control point in the initiation of synapsis or crossing over.

View Article: PubMed Central - PubMed

Affiliation: Department of Molecular and Cell Biology, University of California at Berkeley 94720, USA.

ABSTRACT
We have analyzed the progressive changes in the spatial distribution of telomeres during meiosis using three-dimensional, high resolution fluorescence microscopy. Fixed meiotic cells of maize (Zea mays L.) were subjected to in situ hybridization under conditions that preserved chromosome structure, allowing identification of stage-dependent changes in telomere arrangements. We found that nuclei at the last somatic prophase before meiosis exhibit a nonrandom, polarized chromosome organization resulting in a loose grouping of telomeres. Quantitative measurements on the spatial arrangements of telomeres revealed that, as cells passed through premeiotic interphase and into leptotene, there was an increase in the frequency of large telomere-to-telomere distances and a decrease in the bias toward peripheral localization of telomeres. By leptotene, there was no obvious evidence of telomere grouping, and the large, singular nucleolus was internally located, nearly concentric with the nucleus. At the end of leptotene, telomeres clustered de novo at the nuclear periphery, coincident with a displacement of the nucleolus to one side. The telomere cluster persisted throughout zygotene and into early pachytene. The nucleolus was adjacent to the cluster at zygotene. At the pachytene stage, telomeres rearranged again by dispersing throughout the nuclear periphery. The stage-dependent changes in telomere arrangements are suggestive of specific, active telomere-associated motility processes with meiotic functions. Thus, the formation of the cluster itself is an early event in the nuclear reorganizations associated with meiosis and may reflect a control point in the initiation of synapsis or crossing over.

Show MeSH
Related in: MedlinePlus