Limits...
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.

Show MeSH
Criteria for staging meiocytes after FISH. A summary of the multiple criteria used to determine meiotic stages in maize meiotic is shown, along with DAPI images of representative nuclei (FITC telomere signals not shown). DAPI images are shown as single  optical sections (A and B) or projections of optical sections spanning 2–3 microns in the Z dimension (C, D, and E). Each image is from  a data stack subvolume originally containing an entire nucleus (see Materials and Methods). Chromatin and chromosome fiber appearances, the most definitive characteristics of meiotic stages, are considered together with anther size, nucleolus position, and knob morphology in classifying individual nuclei. Asterisks (*) indicate those criteria established in part or in full from this study; additional staging criteria are taken in part or in full from the literature (12, 22, 23, 46). Heterochromatic knobs (k), condensed fibers (f), and the  position of the nucleolus (n) are indicated. The five conventional stages of the prophase of meiosis I (leptotene, zygotene, pachytene,  diplotene, and diakinesis) are indicated at the top. Chromosomes of leptotene, zygotene, and pachytene nuclei are not yet synapsed,  partially synapsed, or completely synapsed, respectively. Chromosomes of diplotene and diakinesis have desynapsed and are further  condensed. Additionally, premeiotic interphase and prezygotene (Pzt, and see text) are indicated.
© Copyright Policy
Related In: Results  -  Collection


getmorefigures.php?uid=PMC2139864&req=5

Figure 1: Criteria for staging meiocytes after FISH. A summary of the multiple criteria used to determine meiotic stages in maize meiotic is shown, along with DAPI images of representative nuclei (FITC telomere signals not shown). DAPI images are shown as single optical sections (A and B) or projections of optical sections spanning 2–3 microns in the Z dimension (C, D, and E). Each image is from a data stack subvolume originally containing an entire nucleus (see Materials and Methods). Chromatin and chromosome fiber appearances, the most definitive characteristics of meiotic stages, are considered together with anther size, nucleolus position, and knob morphology in classifying individual nuclei. Asterisks (*) indicate those criteria established in part or in full from this study; additional staging criteria are taken in part or in full from the literature (12, 22, 23, 46). Heterochromatic knobs (k), condensed fibers (f), and the position of the nucleolus (n) are indicated. The five conventional stages of the prophase of meiosis I (leptotene, zygotene, pachytene, diplotene, and diakinesis) are indicated at the top. Chromosomes of leptotene, zygotene, and pachytene nuclei are not yet synapsed, partially synapsed, or completely synapsed, respectively. Chromosomes of diplotene and diakinesis have desynapsed and are further condensed. Additionally, premeiotic interphase and prezygotene (Pzt, and see text) are indicated.

Mentions: Fig. 1 shows representative DAPI images of staged nuclei following successful in situ hybridization. These images illustrate that nuclei and the chromosomes within them were well preserved. The morphological detail seen in the DAPI images is used in conjunction with several other criteria to stage the meiocytes. Although meiocytes from a single anther are synchronous, we typically pooled meiocytes from 3–6 similarly sized anthers on each slide. Consequently, stages were identified on a nucleus by nucleus basis using the criteria detailed in Fig. 1 (see legend). The multiple criteria for staging are detailed here because proper staging is essential for accurately sorting out the temporal relationships among multiple meiotic processes.


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)

Criteria for staging meiocytes after FISH. A summary of the multiple criteria used to determine meiotic stages in maize meiotic is shown, along with DAPI images of representative nuclei (FITC telomere signals not shown). DAPI images are shown as single  optical sections (A and B) or projections of optical sections spanning 2–3 microns in the Z dimension (C, D, and E). Each image is from  a data stack subvolume originally containing an entire nucleus (see Materials and Methods). Chromatin and chromosome fiber appearances, the most definitive characteristics of meiotic stages, are considered together with anther size, nucleolus position, and knob morphology in classifying individual nuclei. Asterisks (*) indicate those criteria established in part or in full from this study; additional staging criteria are taken in part or in full from the literature (12, 22, 23, 46). Heterochromatic knobs (k), condensed fibers (f), and the  position of the nucleolus (n) are indicated. The five conventional stages of the prophase of meiosis I (leptotene, zygotene, pachytene,  diplotene, and diakinesis) are indicated at the top. Chromosomes of leptotene, zygotene, and pachytene nuclei are not yet synapsed,  partially synapsed, or completely synapsed, respectively. Chromosomes of diplotene and diakinesis have desynapsed and are further  condensed. Additionally, premeiotic interphase and prezygotene (Pzt, and see text) are indicated.
© Copyright Policy
Related In: Results  -  Collection

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

Figure 1: Criteria for staging meiocytes after FISH. A summary of the multiple criteria used to determine meiotic stages in maize meiotic is shown, along with DAPI images of representative nuclei (FITC telomere signals not shown). DAPI images are shown as single optical sections (A and B) or projections of optical sections spanning 2–3 microns in the Z dimension (C, D, and E). Each image is from a data stack subvolume originally containing an entire nucleus (see Materials and Methods). Chromatin and chromosome fiber appearances, the most definitive characteristics of meiotic stages, are considered together with anther size, nucleolus position, and knob morphology in classifying individual nuclei. Asterisks (*) indicate those criteria established in part or in full from this study; additional staging criteria are taken in part or in full from the literature (12, 22, 23, 46). Heterochromatic knobs (k), condensed fibers (f), and the position of the nucleolus (n) are indicated. The five conventional stages of the prophase of meiosis I (leptotene, zygotene, pachytene, diplotene, and diakinesis) are indicated at the top. Chromosomes of leptotene, zygotene, and pachytene nuclei are not yet synapsed, partially synapsed, or completely synapsed, respectively. Chromosomes of diplotene and diakinesis have desynapsed and are further condensed. Additionally, premeiotic interphase and prezygotene (Pzt, and see text) are indicated.
Mentions: Fig. 1 shows representative DAPI images of staged nuclei following successful in situ hybridization. These images illustrate that nuclei and the chromosomes within them were well preserved. The morphological detail seen in the DAPI images is used in conjunction with several other criteria to stage the meiocytes. Although meiocytes from a single anther are synchronous, we typically pooled meiocytes from 3–6 similarly sized anthers on each slide. Consequently, stages were identified on a nucleus by nucleus basis using the criteria detailed in Fig. 1 (see legend). The multiple criteria for staging are detailed here because proper staging is essential for accurately sorting out the temporal relationships among multiple meiotic processes.

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