Structural evidence for elastic tethers connecting separating chromosomes in crane-fly spermatocytes

Area of Science:

• Cell Biology
• Cytogenetics

Background:

• Anaphase bridges are observed during cell division.
• Laser microsurgery studies suggested elastic tethers connect telomeres of separating chromosomes in animal cells.
• Structural evidence for these telomeric tethers was previously lacking.

Purpose of the Study:

• To investigate the existence and structure of visible connections between separating telomeres during meiosis I in crane-fly primary spermatocytes.
• To correlate live imaging with electron tomography to visualize these structures.

Main Methods:

• Live imaging of meiosis I in crane-fly primary spermatocytes.
• Electron tomography to examine structures between separating telomeres.
• Correlation of dynamic live imaging with high-resolution structural analysis.

Main Results:

• Visible structures were consistently found extending between separating telomeres throughout anaphase.
• These structures comprised two components: a darkly stained, chromatin-like part and a lightly stained, filamentous part.
• In later anaphase, the filamentous component remained extended between telomeres while the chromatin-like component retracted.

Conclusions:

• The observed structures provide the first direct structural evidence for the elastic tethers inferred from previous laser-cutting experiments.
• These structures likely represent the functional tethers connecting separating telomeres during anaphase.
• Elastic tethers are probably a conserved feature present during anaphase in all animal cells.