Fig. 12

Schematic diagram of arrested mitosis (lower panel) in comparison with normal mitosis (upper panel). a Prophase. Due to the enlargement of cell bodies and primary processes in reactive astrocytes, many astral microtubules penetrate into the processes and pull centrosomes away from nuclei (arrow indicates a pulling centrifugal force applied to centrosome). Note that these forces may also pull on the plasma membrane, causing retraction of processes. b Metaphase. In arrested mitosis astral, polar and kinetochore microtubules lack a normal arrangement; several pole-like complexes are formed and include NUMA, γ-tubulin, TPX2; chromosomes cannot be congressed at a metaphase plate and consequently correct segregation is not fulfilled. Note, one chromosome is located outside of the metaphase plate in this diagram . Furthermore, in a normal metaphase, soluble proteins, such as GFAP, vimentin, and alphaB-crystallin, are excluded from the spindle area, whereas in the enlarged astrocytes, however, these proteins are not excluded, and intercalate between chromosomes and spindles (note border between lighter area of spindle and darker cytoplasm in the upper Figure, and the absence of such a border in the lower Figure). c Isolated or groups of chromosomes are covered with nuclear envelopes with formation of micronuclei