Connections between sister and non-sister telomeres of segregating chromatids maintain euploidy.

The complete separation of sister chromatids during anaphase is a fundamental requirement for successful mitosis. Therefore, divisions with either persistent DNA-based connections or lagging chromosome fragments threaten aneuploidy if unresolved. Here, we demonstrate the existence of an anaphase mechanism in normally dividing cells in which pervasive connections between telomeres of segregating chromosomes aid in rescuing lagging chromosome fragments.

Visualizing the Dynamics of Cell Division by Live Imaging Drosophila Larval Brain Squashes.

The dramatic changes of subcellular structures during mitosis are best visualized by live imaging. In general, live imaging requires the expression of proteins of interest fused to fluorophores and a model system amenable to live microscopy. Drosophila melanogaster is an attractive model in which to perform live imaging because of the numerous transgenic stocks bearing fluorescently tagged transgenes as well as the ability to precisely manipulate gene expression.

Kinetochore-independent mechanisms of sister chromosome separation.

Although kinetochores normally play a key role in sister chromatid separation and segregation, chromosome fragments lacking kinetochores (acentrics) can in some cases separate and segregate successfully. In Drosophila neuroblasts, acentric chromosomes undergo delayed, but otherwise normal sister separation, revealing the existence of kinetochore- independent mechanisms driving sister chromosome separation. Bulk cohesin removal from the acentric is not delayed, suggesting factors other than cohesin are responsible for the delay in acentric sister separation.

ESCRT-III-mediated membrane fusion drives chromosome fragments through nuclear envelope channels.

Mitotic cells must form a single nucleus during telophase or exclude part of their genome as damage-prone micronuclei. While research has detailed how micronuclei arise from cells entering anaphase with lagging chromosomes, cellular mechanisms allowing late-segregating chromosomes to rejoin daughter nuclei remain underexplored. Here, we find that late-segregating acentric chromosome fragments that rejoin daughter nuclei are associated with nuclear membrane but devoid of lamin and nuclear pore complexes in Drosophila melanogaster.