ABSTRACT

Bass HW, Marshall WF, Sedat JW, Agard DA, Cande WZ (1997)
     Telomeres cluster de novo before the initiation of synapsis: 
     a three-dimensional spatial analysis of telomere positions 
     before and during meiotic prophase. J Cell Biol 137:5-18.

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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